Cooling issue driving me crazy!

[Jeff K]

Ok, here is the back-story

When I did my first resto on my car, 2011. We changed the radiator, thermostat, hoses and water pump.
The car ran perfectly cool, even during 110 degree days in California.

About a year later, it started to have a cooling problem. It slowly heats up. Only on load, it can idle forever.
Nothing has changed.. Weird.

I decided to go Stage 2 and pulled the engine. The bottom end got hot tanked, new rings and bearings and a full valve job.
After install the cooling problem remains, exactly the same way.

I pulled the radiator and brought it to a shop. The dissembled it and cleaned it, although they said it was almost perfectly clean to start with.
I pulled the water pump and checked .. it’s fine.
I changed the thermostat.
Check all the hard tubes from the gas tank to the back of the car.
The system does not lose any coolant.

The cooling system will hold 15lb of pressure indefinitely. (I have a pressure tester)

Any clues? I did all the proper bleeding procedures.

Maybe as simple as a clogged tube in the front.. or a bad check valve somewhere. Maybe something with the heater core?
Any suggestions?

Thanks
Jeff

[Michael]

Assuming everything is working correctly (both fans running in the right direction, proper pressure, etc.) Sounds like a water pump problem.

[Jonathan]

Assuming everything is working correctly (both fans running in the right direction...

More to this...

Can you confirm how and when your fans turn on?

Do they turn on when the A/C compressor clutch is pulled in?
Do they turn on and off again based on the otterstat/coolant temperature? What does the temperature gauge read when they either turn on or turn off?

[Jeff K]

I'll add a bit more.

The fans turn on at the right temperature. They turn on with the Ac too. (Verified with laser thermometer)

It gets hot when going uphill, but I don't think it's the engine load, I think an air bubble is going to the top of the system.

It cools off when going downhill fast.

[DeLorean03]

Sounds possibly like a thermostat. I used to have an issue where driving my temp gauge would go up but idling it would go down. Changed my thermostat, and if I recall correctly, the problem went away. It had been changed in 2004, and this behavior had started in 2007.

[Jeff K]

Sounds possibly like a thermostat. I used to have an issue where driving my temp gauge would go up but idling it would go down. Changed my thermostat, and if I recall correctly, the problem went away. It had been changed in 2004, and this behavior had started in 2007.

I thought so too, but I tried two DMC thermostats. New Radiator cap too. 16lbs

Does the thermostat have to have a certain orientation? IE direction? I'm guessing no but you never know with these cars.

Never ever had a baffling cooling issue like this before, and I take a car to the track semi-monthly (Not this car of course!)

[hmcelraft]

I had a new engine installed and I could not get it to run "normal". With the old engine I never seemed to have a problem getting the air out but, the new engine seemed to always run hot. I did all the things you have mentioned to the cooling system plus testing the coolant for a blown head gasket which was negative. I tried to bleed air by doing everything except putting the car on-end. Bottom line - I finally did a vacuum on the cooling system and refilled it with the vacuum. Cooling system seems "normal" now. I've driven several hot days this year with 93F using the AC and doing some freeway driving. I've gone several thousand miles now - at least 4,000 - after the vacuum refill. The coolant level is holding solid with temps normal. When I change the coolant again in another year or so you can bet that is the way I intend to refill.

[Jeff K]

I had a new engine installed and I could not get it to run "normal". With the old engine I never seemed to have a problem getting the air out but, the new engine seemed to always run hot. I did all the things you have mentioned to the cooling system plus testing the coolant for a blown head gasket which was negative. I tried to bleed air by doing everything except putting the car on-end. Bottom line - I finally did a vacuum on the cooling system and refilled it with the vacuum. Cooling system seems "normal" now. I've driven several hot days this year with 93F using the AC and doing some freeway driving. I've gone several thousand miles now - at least 4,000 - after the vacuum refill. The coolant level is holding solid with temps normal. When I change the coolant again in another year or so you can bet that is the way I intend to refill.

You have the exact same thing as I do.

What vacuum system did you use? Did you go to a shop or buy one?

Thanks!
Jeff

[Jonathan]

Does the thermostat have to have a certain orientation? IE direction? I'm guessing no but you never know with these cars.

Do you mean like which way it is pointed in the pipe (like you would if it were check valve)? I am assuming you aren't asking about the orientation of the "tee" in which it sits? The consensus for eliminating that air trap spot is to rotate the tee to face down and so your wiring connections would then be from underneath. Pointing up tends to be a spot for air to get in and mess with the readings.

[NightFlyer]

If you're not familiar with my flush and refill procedure (which if followed precisely prevents you from having to bleed the cooling system at all), it can be found here:

http://www.dmctoday.com/showthread.php?682-Coolant-Flush-and-Refill-Procedure-To-Avoid-Bleeding

As you know that your system is leak free, the only place that air could be introduced into the system when driving on steep inclines is via the header bottle. My solution to this problem is to keep the header bottle over-filled. As long as you're not pushing the thermal limits of the system, you should be able to keep the bottle slightly overfilled without having the excess coolant purged by the system, which should prevent air from infiltrating the system. You could also try baffling the header bottle, which should also work, although I've never personally tried this, as it hasn't been necessary.

When the vendors started manufacturing replacement header bottles, I don't know why they didn't redesign them to orient vertically as opposed to horizontally, as doing so would prevent such a problem from ever occurring, regardless of the grade you're experiencing with your vehicle. Apparently it's not a widespread enough of an issue for anyone to address with a mass availability solution.

[hmcelraft]

It was a desperate time when I decided to try something a friend of mine suggested who is a technician at an exotic car service center.

When I did mine originally I drained about a 1/3 of the coolant out and rigged an old Stant 15lb "closed system" coolant cap (the kind that isolates the overflow area and hose on the coolant tank). I had to remove the center relief wafer. I then used my hand vacuum pump attached to the overflow hose to pull the vacuum. I also connected the little reservoir for the vacuum pump in case I happen to pull coolant into the vacuum line attachment and pulled over 20 in of vacuum. My friend recommended at least 20 inches or more. It was a lot of pumping. After letting the vacuum hold for about 5-10 minutes to see if the vacuum would hold, I pinched the hose with my fingers, disconnected the vacuum line from the hand pump and stuck it into a bucket of coolant mixed 50-50 (almost 2 gallons of coolant). Released the pinch and the system filled up. That was it. I did end up doing some "topping off" but not much. The small vacuum line was a bit of a slow fill but ok.

What was interesting, as I was pulling the vacuum on the system I could her gurgles??? Anyway it seems to have worked.

I have looked at several of the vacuum refill tools on-line for around $50-$75 with the convenient valves, etc. that are run by air pressure from my air compressor - that is my next purchase.

[David T]

It was a desperate time when I decided to try something a friend of mine suggested who is a technician at an exotic car service center.

When I did mine originally I drained about a 1/3 of the coolant out and rigged an old Stant 15lb "closed system" coolant cap (the kind that isolates the overflow area and hose on the coolant tank). I had to remove the center relief wafer. I then used my hand vacuum pump attached to the overflow hose to pull the vacuum. I also connected the little reservoir for the vacuum pump in case I happen to pull coolant into the vacuum line attachment and pulled over 20 in of vacuum. My friend recommended at least 20 inches or more. It was a lot of pumping. After letting the vacuum hold for about 5-10 minutes to see if the vacuum would hold, I pinched the hose with my fingers, disconnected the vacuum line from the hand pump and stuck it into a bucket of coolant mixed 50-50 (almost 2 gallons of coolant). Released the pinch and the system filled up. That was it. I did end up doing some "topping off" but not much. The small vacuum line was a bit of a slow fill but ok.

What was interesting, as I was pulling the vacuum on the system I could her gurgles??? Anyway it seems to have worked.

I have looked at several of the vacuum refill tools on-line for around $50-$75 with the convenient valves, etc. that are run by air pressure from my air compressor - that is my next purchase.

There are vacuum extractors used to pull a vacuum using compressed air so you can suck coolant into all of the areas of the cooling system. Doesn't eliminate bleeding air but reduces the amount and time considerably. Not required though. I would suggest two things. Make sure the thermostat has a bleeder hole to allow air to pass. Not all thermostats have one so if yours doesn't just drill a 1/16" hole in it. The other thing to do is pressurize the system and bleed the air out the bleeder nipple on the thermostat housing AND loosen the small hose on the top, left side of the radiator to let air out.

[Spittybug]

Do you know your gauge to be good? Have you verified actual temperature versus what your gauge says it is? Or maybe a wonky sender?

[sdg3205]

I agree with Owen. Between the sensor connection, sensor itself, bulkhead plugs and binnacle circuit board there are a few places corrosion could be interfering. I once had to clean every single connection to get an accurate reading.

It sounds like you've got the mechanicals covered.

[DeLorean03]

Do you know your gauge to be good? Have you verified actual temperature versus what your gauge says it is? Or maybe a wonky sender?

Excellent point. I remember mine went bad as it was constantly reading over 220, and we had a laser thermometer reading of 187F. Yes, definitely make sure this is working right.