tap tap tap

[dustybarn]

I've got a persistent engine noise that I'm having trouble diagnosing:

-Once per engine cycle (every other rev)
-Present at idle and every engine speed. It speeds up with the engine but does not change in basic character regardless of speed
-Does not change with engine load
-Shorting plug leads did not affect it

It sounds like a very loosely-adjusted valve, but I pulled both valve covers, checked the clearances, and found nothing amiss. While I had the valve covers off, I looked for signs that a rocker arm might be hitting a valve cover, and saw no evidence.

The ear pretty easily localizes it to the starboard cylinder bank; it can be heard most clearly through a stethoscope on the starboard valve cover and on the intake manifold.

Does anyone have any suggestions? I'm sorta stumped.

[Ron]

Small exhaust leaks can sound amazingly close to valve train noise.
Try this- With the engine cool, turn your water hose down to a small stream and run it around all of the exhaust system seams, especially the bottom of the manifold where it meets the head.
Or, pull your plug wires one at a time and see if the noise changes or goes away.

[opethmike]

Agreed on the exhaust manifold leak possibility. I've seen on several cars (not limited to just DeLoreans) where it REALLY sounds like a valve train issue, but turned out to be an exhaust manifold/gasket issue.

Try taking a look at your cylinder head where the exhaust manifold is mounted. Do you see soot/black dust in the area?

I know you live not too far from me. I could help you take a look at the issue at some point, if you would like.

[DMCMW Dave]

A worn rocker arm will do this. It will also seem to go out of adjustment very quickly as the hardened surface of the arm is gone.

The key to me is that he said it does not change under load, if that is true it is probably not an exhaust leak.

It's possible to loosen suspect arm adjusters and inspect the surface with a mirror. It should not be concave.

[dustybarn]

A worn rocker arm will do this. It will also seem to go out of adjustment very quickly as the hardened surface of the arm is gone.

The key to me is that he said it does not change under load, if that is true it is probably not an exhaust leak.

It's possible to loosen suspect arm adjusters and inspect the surface with a mirror. It should not be concave.

Hmm. I need to verify that the volume doesn't change with load. I have a loudish exhaust and the noise is audible at idle and all other load conditions...I'm wondering if it is in fact varying with load but its apparent loudness is more-or-less the same.

[Some guy]

I have that problem with my car. I know the valves need to be adjusted, but i used magic mystery oil to knock down a lot of the noise. The other problem was that one of the bolts on the catalytic converter is gone. So once i get the new cat i should have a mostly quite car.

[Ron]

Oops, nix the "...pull the plug wires" idea...I just noticed you shorted them all.

[dustybarn]

Thanks, everyone, for your input. I've gone back and done some more investigating:

It does not appear to be an exhaust leak.

I can hear it most clearly with the stethoscope probe against the side of the starboard cylinder head, between the #2 and #3 exhaust ports. It definitely sounds mechanical through the stethoscope, and does not respond to engine load. None of the valve clearances are loose.

I'm starting to think about all the possibilities; what things could be hitting other things at 1/2 crank speed? Could the camshaft be mistimed, causing a valve to kiss a piston? I know the engine has non-stock cams (I found a cam data sheet in the glovebox).

Any more ideas?

[Jonathan]

Hey Dusty,

Just for reference, here's a video of my car before an exhaust leak was fixed by replacing the gaskets:


http://www.youtube.com/watch?v=t2yvgO3lNkE&feature=plcp

And after waiting 30 seconds, I'll post the after video in a second video clip...

[Jonathan]

After exhaust manifold gaskets were replaced for your reference:


http://www.youtube.com/watch?v=EPhH_NowHh8&feature=plcp

[dustybarn]

The cam lobe and undoubtedly the follower surface is badly worn on #2's exhaust valve opening ramp. I finally pulled the valve cover again and carefully inspected each cam surface, rotating the engine about 45 degrees at a time. That explains why the clearances always checked OK. While it's a bit of a PITA to change the cam, it's not as bad as it could be. Thanks to all for your help.

[David T]

That is unusual. I would suspect the motor oil (wrong type) low motor oil, infrequent oil changes, etc. What is the history on the car? The B28F used in the Delorean does not have a lot of problems with the cams (unlike the previous, earlier versions). I would carefully inspect the other cam too. It wouldn't hurt to do a leak-down test on each cylinder and a compression test with and without oiling the cylinders to see if you have a lot of ring wear.
David Teitelbaum

[dustybarn]

That is unusual. I would suspect the motor oil (wrong type) low motor oil, infrequent oil changes, etc. What is the history on the car? The B28F used in the Delorean does not have a lot of problems with the cams (unlike the previous, earlier versions). I would carefully inspect the other cam too. It wouldn't hurt to do a leak-down test on each cylinder and a compression test with and without oiling the cylinders to see if you have a lot of ring wear.
David Teitelbaum

I checked leakdown on the affected bank, and they all were good and identical. I know that they are not stock cams, they're from Race Cams, Inc. of Ft. Lauderdale and probably are only a few years younger than the car. I plan on replacing both of them as a matter of course. The car has maybe 75000 miles on it.

[David T]

Well, that would explain it. The cams probably did not have the proper hardening. Best to get those cams out of the motor now. My suggestion would be to go back to stock, drive the car around 500 miles or so and then do an oil change.
David Teitelbaum

[Ron]

+1

[Azar]

Hello, bringing up this thread. Did it sound similar? It is louder when warm. Oil is fresh, Castrol GTX 20W-50. The oil pressure is very low at idle and warm though....
https://photos.app.goo.gl/hd1tysQgsW8xZsis5

Thanks!

[Azar]

here for example this owner changed Timing Chain tensioners, guides, replaced both heads, New Cams, and New Rockers, New Valve guides, and had the valves lapped in. Also replaced the pulley wheels - still same so he got a new engine!
https://www.youtube.com/watch?v=JFXllpATMdE

[mark w]

here for example this owner changed Timing Chain tensioners, guides, replaced both heads, New Cams, and New Rockers, New Valve guides, and had the valves lapped in. Also replaced the pulley wheels - still same so he got a new engine!
https://www.youtube.com/watch?v=JFXllpATMdE

i have a question too. if you change the cam, do you need to have the rockers machined to match?

[dmcman73]

i have a question too. if you change the cam, do you need to have the rockers machined to match?

No, unless they are warm then you replace them. Only the adjuster screw needs to be set according to the manual.

[Ron]

Azar,
As the engine warms, the valve train should get tighter (quieter), if anything. Since you have low oil pressure at idle (confirm with external gauge), I would suspect that the oil is getting thinner as it warms, reducing the oil pressure even more... Sounds like the upper half of the engine could be starving for oil because of components in the lower half is worn (crank/bearings/pump/etc).

[Azar]

Azar,
As the engine warms, the valve train should get tighter (quieter), if anything. Since you have low oil pressure at idle (confirm with external gauge), I would suspect that the oil is getting thinner as it warms, reducing the oil pressure even more... Sounds like the upper half of the engine could be starving for oil because of components in the lower half is worn (crank/bearings/pump/etc).Thanks Ron! I will be investigating the pump. First I will change the oil to 10W -40.

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[Ron]

i have a question too. if you change the cam, do you need to have the rockers machined to match?A new cam will wear more during the first few minutes of its break in period than the rest of its life. The rockers (or lifters) must have a fresh mating surface. Otherwise, the cam WILL eventually fail prematurely and you will void its warranty.

FWIW- Once a cam has been broke in, the rocker (or lifter) it was broken in with must stay with it or be replaced with a new one.

According to the manual, the rockers can not be resurfaced.

These 'rules' are not picky, but critical...

[Azar]

Azar,
As the engine warms, the valve train should get tighter (quieter), if anything. Since you have low oil pressure at idle (confirm with external gauge), I would suspect that the oil is getting thinner as it warms, reducing the oil pressure even more... Sounds like the upper half of the engine could be starving for oil because of components in the lower half is worn (crank/bearings/pump/etc).

Hi Ron, it turned out to be valve clearance in the right bank. now it is silent again. But the question about the low oil pressure remains. When the engine is very hot (180-200), which is only after driving for 30 minutes at the +19C, the oil pressure light started to light up at idle (was replaced recently). Will do the oil change and report.

[David T]

Verify oil pressure with an accurate mechanical gauge. The wire going to the oil light is known to get burnt up and short to ground where it passes alongside the motor. Can make the light flicker and light up. Put a firesleeve on the wire. The wrong oil or not enough or a very dirty filter can cause low oil pressure.

[Ron]

Hi Ron, it turned out to be valve clearance in the right bank. now it is silent again. But the question about the low oil pressure remains. When the engine is very hot (180-200), which is only after driving for 30 minutes at the +19C, the oil pressure light started to light up at idle (was replaced recently). Will do the oil change and report.
Without more history, it sounds like the right side may have been too cool when the valve lash was set. It must be done when the engine is at normal operating temp ( 180°F +). Sometimes (especially with aluminum heads/blocks) you have to do one side and then warm it back up before doing the other.) Note that "180-200" is normal and shouldn't take 30 minutes to get there, driving or idling. (A good thermostat will force this.) This has me wondering if your gauge(s) are off and the oil is getting too hot, causing the oil to get too thin...

What is the gauge doing during all this? The light's wire shouldn't affect it. But, I agree with David, get a mechanical pressure gauge. And a way to accurately measure the coolant temp also.
Laser thermometers are <$20. Another type, placed in the hose immediately downstream from the thermostat, is hands free and gives you a more accurate reading of the coolant itself...
Record the pressure and temp when dead cold (sat over night), every 30 seconds as it warms up and at the highest temp it gets. Record the temp when the fans come on. Do the tests with new oil & filter, no additives. If no other red flags here, you are probably looking at worn parts (engine/cam bearings, pump), restricted pickup screen, or internal leak.

Did you inspect the rockers and cam lobes as Dave S suggested earlier in the thread when re-adjusting the right side?

[Azar]

Without more history, it sounds like the right side may have been too cool when the valve lash was set. It must be done when the engine is at normal operating temp ( 180°F +). Sometimes (especially with aluminum heads/blocks) you have to do one side and then warm it back up before doing the other.) Note that "180-200" is normal and shouldn't take 30 minutes to get there, driving or idling. (A good thermostat will force this.) This has me wondering if your gauge(s) are off and the oil is getting too hot, causing the oil to get too thin...

What is the gauge doing during all this? The light's wire shouldn't affect it. But, I agree with David, get a mechanical pressure gauge. And a way to accurately measure the coolant temp also.
Laser thermometers are <$20. Another type, placed in the hose immediately downstream from the thermostat, is hands free and gives you a more accurate reading of the coolant itself...
Record the pressure and temp when dead cold (sat over night), every 30 seconds as it warms up and at the highest temp it gets. Record the temp when the fans come on. Do the tests with new oil & filter, no additives. If no other red flags here, you are probably looking at worn parts (engine/cam bearings, pump), restricted pickup screen, or internal leak.

Did you inspect the rockers and cam lobes as Dave S suggested earlier in the thread when re-adjusting the right side?

Thanks Ron, I will try to answer step by step
- I did the valve adjustment when cold, so 0,1mm intake and 0,25mm exhaust, as per manual. the previous clearance was greater.
- perhaps my thermostat is always open. but it was 25 minutes ride and we were still at 170F. The fans kicked in after 30 minutes and standing at 200F and reduced the temp to 160F before switching off
- Ordered mechanical pressure gauge, arrives today or tomorrow. Can I measure it on the drivers side, there the oil pressure light switch is? or only on the passenger side where the sensor for the gauge is? I need a crushable washer, which I don;t have now...
- I have an infrared Thermometer, will try to measure the hoses. but you are right, probably not accurate? I think I remember the hoses being hot after the engine start, means perhaps my thermostat is stuck open. had this on my BMWs
- Restricted Pickup Screen and Oil pump - can I inspect them by just dropping the oil pan? I presume I need a new oil pan gasket then.

- I did unscrew one rocker (I hope I got it right? the rocker is the screw which I adjust?) but forgot to make a picture. I am not an expert but there was a slight wear pattern on them like on the hammer. I did make the photos of the cam lobes - attached.

https://photos.app.goo.gl/mR9XKJGzYGBAPXq18 - here are also the videos before and after the valve adjustment.

Many thanks for your support!

[Azar]

Verify oil pressure with an accurate mechanical gauge. The wire going to the oil light is known to get burnt up and short to ground where it passes alongside the motor. Can make the light flicker and light up. Put a firesleeve on the wire. The wrong oil or not enough or a very dirty filter can cause low oil pressure.Thanks Dave, will do! Appreciate your help!
I was under the car and the oil pressure gauge sender on the passenger side is not easy to remove. Can I measure it on the otherwise instead?

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[Ron]

Thanks Ron, I will try to answer step by step
- I did the valve adjustment when cold, so 0,1mm intake and 0,25mm exhaust, as per manual. the previous clearance was greater.
- perhaps my thermostat is always open. but it was 25 minutes ride and we were still at 170F. The fans kicked in after 30 minutes and standing at 200F and reduced the temp to 160F before switching off
- Ordered mechanical pressure gauge, arrives today or tomorrow. Can I measure it on the drivers side, there the oil pressure light switch is? or only on the passenger side where the sensor for the gauge is? I need a crushable washer, which I don;t have now...
- I have an infrared Thermometer, will try to measure the hoses. but you are right, probably not accurate? I think I remember the hoses being hot after the engine start, means perhaps my thermostat is stuck open. had this on my BMWs
- Restricted Pickup Screen and Oil pump - can I inspect them by just dropping the oil pan? I presume I need a new oil pan gasket then.

- I did unscrew one rocker (I hope I got it right? the rocker is the screw which I adjust?) but forgot to make a picture. I am not an expert but there was a slight wear pattern on them like on the hammer. I did make the photos of the cam lobes - attached.

https://photos.app.goo.gl/mR9XKJGzYGBAPXq18 - here are also the videos before and after the valve adjustment.

Many thanks for your support!
Seems you have the valve clearances correct. Just in case:
64404
This is from the Volvo Service Manual, Pg. 59.
But, follow the spec sheet if an aftermarket cam.

Sounds like thermostat needs attention to me.

Rule of thumb is check oil pressure at the place furthest from the oil pump. But either place should be OK, assuming the gauge reads low too...?

Infrared units are very accurate. The problem is reaction time and hitting the correct spot, I.E., you can shoot the thermostat housing and the attaching bolts an inch away and get 3 different readings, and, the metals take time to heat/cool, at different rates. Keep this in mind and I'd say you can use one here, since the temps are so far off.

You can see the screen with the pan off, or a bore-scope...
Looks pretty clean under the valve covers, FWIW.

Yes, the screw you adjust is on one side of the rocker/follower. The other side mates to the cam. Compare the wear to ones that didn't need adjusting.
What seems to be #3 intake (single lobe in pic) appears a bit worn. It's hard to tell...maybe only scuff marks from trash etc. Did you happen to see if you could feel the edge of the wear with a fingernail. If you can feel it, it's time to replace it before it breaks down and the loose metal trashes the rest of the engine. The mating surface is harder, so once it starts, it breaks down very fast.

[Azar]

Thanks Ron! I will do the tests. I noticed that I have an oil leak under the engine. Not sure where it is coming from. The Valve covers are dry. Mostly it is wet near the right motor mount and the lower part of the generator. The sensors and oil filter are dry. Can this be the reason for the low oil pressure?https://uploads.tapatalk-cdn.com/20200905/4aca75ee901f8330e5498b7a731350c5.jpghttps://uploads.tapatalk-cdn.com/20200905/a30957f9d26e95e49f5f5f884cc1a389.jpghttps://uploads.tapatalk-cdn.com/20200905/7db8b7b12d5340f4f3c623f19f0f73c4.jpghttps://uploads.tapatalk-cdn.com/20200905/82e0e99f9fa8fa159a2a412ec7e928bb.jpghttps://uploads.tapatalk-cdn.com/20200905/7fc9cd72d52b8b67c7e3fd4ca717efb0.jpghttps://uploads.tapatalk-cdn.com/20200905/28eecdf15f1fc1f882336ffe8d25833a.jpg

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[Ron]

YW!

It doesn't look like the leak would cause low oil pressure, unless it lost so much that the level got very low and damaged the bearings/etc.
If you are sure it isn't the valve cover, check: the cam plate on the end of the head, the oil gauge sending unit, and the starter's port (rear seal leak?). Chase the stains from front to back/to the highest point.

[Azar]

The level is at max. Probably starter, did not know that it has seal with the motor.
So I decided to change the oil. It is not very dirty (jest a couple of hundred kilometres) but very thick. It's +15C here. What worries me is the amount of metal on the magnet (new style oil drain plug).
The filter looks clean - does it make sense to cut it and see what's inside?
I have a small camera on the cable and put it in but couldn't find the oil pickup tube. I suspect it might be plugged. I will start the engine tomorrow and note the pressure.
Currently with the cold start it's approx 20 psi (fluctuating 15-30psi due to idle hunt) and 45 psi at 3000 Rpm (according to panel gauge).
https://uploads.tapatalk-cdn.com/20200905/4273a8518639f22b8a957b09b6bc3026.jpghttps://uploads.tapatalk-cdn.com/20200905/c980ef5eaacb02181eec0eb11af3c099.jpghttps://uploads.tapatalk-cdn.com/20200905/23ef400715bc84f23243210386740307.jpg

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[Ron]

To be clear, the starter doesn't have a seal. If there is oil leaking from the rear main seal, it can get slung'/drip and come out around the starer where it goes through to reach the flywheel... Wind can blow it back and make it spread.

That looks like a lot of metal to me too, especially if you recently changed the oil.
Can't hurt to look inside the filter...could be clogging up from the looks of things. Dunno.

I wouldn't get too worried until you get a mechanical gauge on it.

[David T]

That is a LOT of ferrous metal! Way more than you should see. I would do a compression test, get an accurate pressure gauge on the oil system, and a leak-down test to see what has been damaged. My guess is rings. When you pull the spark plugs, see if they are oily. Might want to measure valve lift to see if the cams are damaged too. With that much metal, it is no surprise you have low oil pressure. When you cut the filter open you will probably find a lot more metal.

[mark w]

That is a LOT of ferrous metal! Way more than you should see. I would do a compression test, get an accurate pressure gauge on the oil system, and a leak-down test to see what has been damaged. My guess is rings. When you pull the spark plugs, see if they are oily. Might want to measure valve lift to see if the cams are damaged too. With that much metal, it is no surprise you have low oil pressure. When you cut the filter open you will probably find a lot more metal.

that kind of dark gray sludge like grease is ground up metal. time to rebuild. my fear with low oil pressure is that you have an excessively scored/worn oil pump bore.
before you tear down the whole thing, maybe pull the timing cover and the oil pump and inspect that, in addition to what David T said

[Ron]

That is a LOT of ferrous metal! Way more than you should see. I would do a compression test, get an accurate pressure gauge on the oil system, and a leak-down test to see what has been damaged. My guess is rings. When you pull the spark plugs, see if they are oily. Might want to measure valve lift to see if the cams are damaged too. With that much metal, it is no surprise you have low oil pressure. When you cut the filter open you will probably find a lot more metal.

+1 ...that much/quick and it not knocking, sounds like cam (?now adjusted out?).


that kind of dark gray sludge like grease is ground up metal. time to rebuild. my fear with low oil pressure is that you have an excessively scored/worn oil pump bore.
before you tear down the whole thing, maybe pull the timing cover and the oil pump and inspect that, in addition to what David T said

+1... Showing 45lbs, but, the pump has definitely had a bad diet.

Hmm,...the pics of cams don't look like they've been eating at the same place, to me. (Too 'clean'??)
:headscratch::dunno:

[Azar]

Thanks to all! I will measure the compression and will try to measure the oil pressure. My neighbours are not very happy with me running DeLorean since "it stinks"...

Yes, the cold oil pressure is there (but these numbers, 15 idle and 57 at 3000 rpm should be also with hot oil), the cams look not bad.

I have a feeling that the oil pickup tube/mesh is dirty, probably it's a good time to drop the oil pan and inspect? Will I also see the pump?

I am wondering what is the reason for all this wear...the car ran only a couple of hundred miles since last oil change. Before that it was standing for half year (according to the previous owner, may be longer since it was not running and we had to rebuilt whole gas tank pump unit).



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[Azar]

Filled in 10W-40 Castrol GTX. Interestingly, the gauge showing more stable pressure, and higher after cold start (+16C) than with the 20W-50. 30-40 psi at idle cold and 50 at 3000 rpm. When the temp gauge showed 130 F the idle went down to 10 and 3000 rpm at 30psi. Further increase in temp (190) showing idle 0 psi and 3000 Rpm 20psi. The fans turn on on 190 and cooled down to 170F.
Interestingly, the oil warning light did not come on today during idling hot at all. The temp was about 5deg lower, too.
Driving down the hill cooled down the engine to 120F so my thermostat is definitely stuck open?

I did not have a chance to hook up the pressure gauge instead of pressure sensor, will do it in one week after my return.

My plan is to drop down the pan and inspect the motor from underneath. Cut the oil filter to check. Perhaps will send the oil sample for testing in the lab.

[Rich_NYS]

Hello, bringing up this thread. Did it sound similar? It is louder when warm. Oil is fresh, Castrol GTX 20W-50. The oil pressure is very low at idle and warm though....
https://photos.app.goo.gl/hd1tysQgsW8xZsis5

Thanks!

I had something similar a few years ago, it was a plugged oiler orifice.

Have you tried using a listening rod to pinpoint the location? When I had the noise, I was able to easily determine where the noise was originating.

[Azar]

I had something similar a few years ago, it was a plugged oiler orifice.

Have you tried using a listening rod to pinpoint the location? When I had the noise, I was able to easily determine where the noise was originating.Thanks. Yes these were the valve clearance issue (please see the discussion above). Yes will drop the pan and inspect the orifice.

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[Rich_NYS]

My issue was an oiler orifice on the rocker (didn't need to drop the pan.)

I used a listening rod to find the location, then a small mirror to inspect the orifice & confirm the blockage.

Sent from my LGL164VL using Tapatalk

[Azar]

I have cut open the oil filter (was a fresh oil change 200 miles ago). Did not find much metal "sand" there like on the magnet of the oil drain plug. Most of them are from me cutting the oil filter with the saw. But found one piece of metal about half an inch long. Wondering if this is also the piece of the filter body.
Will drop the oil pan next.https://uploads.tapatalk-cdn.com/20200915/0f3c9f9c40ada7f71ec4d57161169377.jpghttps://uploads.tapatalk-cdn.com/20200915/da83df38d19b81298faf4de7bd01351c.jpghttps://uploads.tapatalk-cdn.com/20200915/e6765a8ab08e2e9aab9c196eeea93ca3.jpghttps://uploads.tapatalk-cdn.com/20200915/4748409097f62b243e31782301406d4a.jpghttps://uploads.tapatalk-cdn.com/20200915/22db79c9a0226c6ae76a071959461934.jpg

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[Azar]

Do I need to lift the engine to drop the oil pan? Thanks

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[Azar]

Hello and Happy New Year to all!
I have some news and was writing the text here but lost it due to crash:( Have to start again but it is pretty late in Europe so will do tomorrow.
Watch this space :)

[Jonty]

Do I need to lift the engine to drop the oil pan? Thanks

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Yes you do. It’s not much of a fun task. I took loosened the engine mount bolts and used a trolley jack and a peice of wood against the rear timing chain cover and lifted it a few in inches to be able to get my hand in to undo the front bolts. Getting the old gasket off took a few hours..

[Azar]

Yes you do. It’s not much of a fun task. I took loosened the engine mount bolts and used a trolley jack and a peice of wood against the rear timing chain cover and lifted it a few in inches to be able to get my hand in to undo the front bolts. Getting the old gasket off took a few hours..

Thenks! I am planning to use the engine lifter. Why did it take so long to remove the old gasket?

[Jonty]

Thenks! I am planning to use the engine lifter. Why did it take so long to remove the old gasket?

Just because it’s likely an original gasket and it’s effectively fossilised to the pan. You will need to chip it off peice by piece being carful it to damage the pan.

[dn010]

Just because it’s likely an original gasket and it’s effectively fossilised to the pan. You will need to chip it off peice by piece being carful it to damage the pan.

+1. I had to use a die grinder to get rid of my original gasket.

[Azar]

Thank you for all your help here and sorry for hijacking the thread. I have opened a new one and posted the manual gauge readings here:
http://dmctalk.org/showthread.php?18616-Low-Oil-Pressure