Not this $#!* again! (Coolant leak at rear of engine)

[NckT]

I used a hot air gun to completely dry out the valley address then vacuum out any residual dirt. I relayed this until the corners were purely just aluminium and not dirt. Once done I cleaned the aluminium with brake cleaner to degrade it. Once done my personal preference was to paint the area with motorbike engine paint used for aluminium cylinder air cooled cylinder heads for future protection.

Good luck with the project, it'll be worthwhile to change the hoses to silicone ones while you're in there

[David T]

If all of the hoses, seals, gaskets and water pump are original they should all be replaced. You should not reuse the copper seals, Instead you should always use new ones. Just stopping the current leak is not going to "fix" this. When pressure testing, while very useful, you are doing it when the motor is cold and once it heats up you may still have a leak, especially with the old parts. Torque values on old rubber hoses with dirty clamps means nothing.

[DaraSue]

I didn't get much done today b/c I had to make cookies for the Thanksgiving potluck at work tonight, but when I checked this morning there was a little dampness under the smaller hose behind the water pump (the one that I had trouble adjusting the clamp on). So I ended up taking the original clamp off and sticking it back on with the bolt turned so I can actually get to it with a wrench (because it was smaller and more maneuverable and also I wasn't 100% sure I wanted to trust a truckstop clamp inside the engine). I'm still poking around for a higher-res version of that torque spec chart posted upthread but I think I got it to 35-40-ish (the torque wrench is still a tight fit and for some reason that bolt was 9/32 instead of 7mm, which took some effort to figure out).

The hoses should all be fairly new since I had the engine overhauled and practically the whole coolant system replaced last winter. They should last more than 8000 miles, right? The waterpump was replaced (twice) last year, too.

[DMC-81]

Here are a few links for the torque values...

https://www.normagroup.com/norma.nsf...LAMP_TX_en.pdf

https://www.normagroup.com/norma.nsf...tasheet_en.pdf

http://www.groenclamps.nl/files/2014...LAMP-TORRO.pdf

[David T]

Some of the vendors sell silicone hoses and better clamps in their kits. Because you can't retighten anything under the intake manifold silicone is the way to go but you must use special clamps too. If a hose was leaking, overtightening the clamp won't stop the leak. You must remove the hose, clean up the ends and reinstall the hose. Modern coolant contains additives that will try to seal any leak and they build up as deposits between the hose and the pipe where it leaks preventing a good seal. Make sure the "Y" pipe is not leaking at the "O" rings and filling the voids on top of the block.

[DaraSue]

Thanks, I'll double check the clamps tomorrow.

Another thing - how much resistance should I encounter when pumping the pressure tester to 15? It takes a lot of effort just around 12 and I didn't think I was that weak. I'm still nervous that I'm doing something wrong (It's the Stant and I'm using the colored arrows, which is how I thought it worked.)

[DMC5180]

What does the backing ring look like? I don't remember seeing it unless it's still in the mixture unit. Although I found a random O-ring over with the rest of the parts so maybe it came off of there.

The backing ring is brass metal cup shaped piece that the Air pipe O-ring fits into. I could not find a picture of one to post here, but the cross section looks something like this without the dots.

|__ ........... __|

The brass piece retains the O-ring and is pressed into the port in the bottom of the air metering housing.

It looks as though you were able to remove the housing, just look in the hole on the underside to see if the brass cup and O-ring are still in place.

Tip for reinstalling the pipe when the time comes. Disconnect the Rubber elbow hose from the ISM and just work with the pipe for getting it reinserted into the housing. Once it is in place, just rotate the pipe and hose towards the ISM and connect it.

The photo you showed with the large coupler hose bulging would be somewhat normal if the system was under 13-15 psi.

While there are other potential leak points around and behind the pump. The most common repeat leak offender is typically that large coupler hose. There is something about the hot/cold cycling that effects that connection more so than others.

Those connections really need constant tension spring type hose clamps aka GM style clamps. Unfortunately, I’ve yet to find one large enough for that connection.

[Rich]

Another thing - how much resistance should I encounter when pumping the pressure tester to 15? It takes a lot of effort just around 12 and I didn't think I was that weak. I'm still nervous that I'm doing something wrong (It's the Stant and I'm using the colored arrows, which is how I thought it worked.)

That's all normal. You're not doing anything wrong. The Stant tester is a solid tool.

The instruction manual that came with mine says to pump a 15-16psi system "up to the line indicated by the light yellow arrowhead, do not exceed this point". That pressure is higher than 15-16psi.

Go for it.

[DaraSue]

The clamps on the fat hose are 40-60 (as far as I could tell from trying to read it with a dental mirror upside down), and the spec sheet says the torque on that is supposed to be 3+.05 NM, which is just under 30 in-lbs. If I tightened it to 40 in-lbs did I break it and need to replace it?

That fat hose seems to be the culprit in the Valley, b/c it was damp under it again this morning (had leaked enough to get a pool in the crevice underneath it even through a paper towel) but I haven't found any leakage from the forked part of the Y-pipe. And now there are two new leaks, one just forward of the engine bay on the passenger's side: 20171124_103747.jpg and one up front on the driver's side: 20171124_103824.jpg

I'd had the tester pumped to between the 9-11 and 13-14 arrows overnight (where the red line is in this pic: press.jpg) and it didn't really drop noticeably even though it leaked a little.

IDK, before I started messing with it I never saw it leak except for the one by the radiator that I still haven't been able to replicate. I feel like everything I'm doing is just making it worse. Is this normal, to have to redo all the coolant hoses once a year? Should I just put it pack together, let it drip until the snow starts falling and then dump it at the shop for the winter?

[DMC5180]

You can expect that with as many clamps and hose connections on the Delorean, to need to re-tighten a clamp now and then. This is especially true on New hoses that may not have been properly torqued during initial installation. The Rubber goes through a process know as “Cold Flow”. This is where the rubber takes a permanent set leaving the hose clamp impression in the hose. Once the cold flow set has occurred the tension/compression from the clamp is reduced.
This where Constant force spring clamps really work nice. They are always applying a constant rate of force on the hose when the hose is expanding, contracting, softening and hardening from temperature changes.

40 in lbs is fine. Most hose clamps are generically rated 40-60 in lbs for torquing. Unless you strip the screw and feel it skip a tooth while tightening, you should be okay.