Alu M52 Overheating --- Update: Sill having issues

[reelizmpro]

I had the same problems with my S52 swap. Kept randomly overheating. It was due to a bad headgasket. Are you bleeding with the heater on and bottom vents open? Also block test for exhaust gasses in the coolant. They could overpressurize the system and cause the cap to expel fluid. This can be caused by a bad headgasket or cracked head which is fairly common on these engines. I know you said the engine was rebuilt but don't assume anything. Rent a block tester and use new fluid to be certain there are no exhaust gasses in the cooling system.

[ScottSneed]

I had a similar issue with overheating, it would only at idle. New radiator, new water pump, new hoses, new thermostat housing, everything..ended up being my reservoir having a hole I COULD NOT see, it didnt leak coolant but was allowing air in, just a thought.

[moatilliatta]

Pressurize the Vanos, activate the solenoid, check for 8.5mm of travel. There should be some write ups online.


Just have to diagnose with a clear mind, I see flaws in peoples work all the time, it’s hard to be perfect.

[Chilezen]

What do you mean by, do a vanos check, exactly?

I assure you it sounds the same when the temp overheats. I've never noticed temperature affecting the sound directly. Scary to think the head gasket on a new motor could be toast. But I'm on a mission to figure out why in the first place.

Good to know about the temp.

[moatilliatta]

I would do it at the temp your systems seem worse. Pulling plugs hot is fine, don't torque them hot.

Video - I bet its combustion blowing between two cylinders.

Do a vanos check when doing the headgasket.

I actually like doing my compression test super hot. That's where the engine is when pushing it. But for diagnosis , repeat the environment.

[Chilezen]

Cool, thanks for the ideas. I'll see if any of my friends who work in a shop have a leak down tester I could borrow. I'll try that before buying the coolant combustion kit. Silly question, but do you perform the leak down test on a cold or warm engine? I know you aren't supposed to take out plugs from a hot engine, but I guess I could warm it up a bit before testing.

You asked if I've run the car with the cap off; that is how I bled the system, revving the engine with the cap off, but no, not actually driving it. Bubbles almost always came out, up until about 20~ish minutes, thinking that the air pockets were purged.
But there either must be another hidden air pocket which is building excess pressure to push the coolant out from under the reservoir cap, or, the combustion is seeping into the coolant. Thanks, the leak down test should tell me something.

On a related note, I took a video of me accelerating onto a freeway, to show you the pinging/knocking sound. This is about 5 minutes after turning the car on, so it's still a bit cold. I run through a few gears at partial throttle to pick up speed, like normal. Then at 0:15, I just rev the engine with no load. No pinging.

Power delivery seems fine, but I can't be sure because I've never driving this engine when it worked properly. As a reminder, I have a code for a faulty vanos, so that's another consideration.

As the car warms up, after say 20 minutes, the pinging is minimal, much quieter.

I'll update later with results from a leak down test. Thanks guys!

[mjweimer]

You could also put a pressure gauge on the coolant system. I found those combustion gas testers to be hit or miss if you have a slight leak.

Yes, agree. It is a better test method period because you can also pressurize and peek in the cylinders for signs of coolant. I just assume no one has that equipment/adapter on hand and it seems like this thing has a fairly large leak.

[moatilliatta]

You could also put a pressure gauge on the coolant system. I found those combustion gas testers to be hit or miss if you have a slight leak.

Have you done leak down test? Or just run it with the cap off to see if it pukes air out?

Ive had head gaskets blow between cylinder intermittent feel like a miss.

[mjweimer]

Interesting that your exhaust pipes are "caked with soot" but your plugs look really clean...I'd think that the plugs would be much darker if the car was running rich.


If you want to try one more test before taking it into a shop, I would try to test the cooling system for combustion gasses.

https://www.lislecorp.com/specialty-tools/combustion-leak-detector

There is also a cheaper version at harbor freight that is endlessly out of stock.


Easy to use and would give you some more knowledge before going back to the shop that did the engine work.

[Chilezen]

For fun, here are the spark plugs. They look okay for only running about a thousand miles?









Only 4 pics but the last two look the same.

My exhaust pipes are caked with soot.

I'd love to install a wideband in the future.

[Chilezen]

Forgot to mention, there's a leak from the rad sensor too:



I'm ruling out that a stock fan will solve these problems, as I've switched on the fan manually after a couple minutes, after hitting 50*C. This helps prolong and reduce the issue slightly, but not enough.

I haven't changed the water pump. I've considered it could be a problem, not pushing enough water through, however, the car runs fine after a while, so the pump must be working. To a degree, at least.

[Chilezen]

Update, still haven't solved the problem.

I'm tired and caving, I haven't got the time to keep troubleshooting, I'm sending it to a shop.

I have replaced the coolant reservoir, the cap, the rear cylinder head coolant gasket, and the heater core (and those o-rings there). The coolant still leaks from the reservoir and the rear of the engine.

I also bought the Bavarian Autosport coolant bleeding funnel kit, the kind that you screw a cap onto the res and put a funnel on that cap, and fill it with water, so that the water is at a higher level to help get bubbles out. The kit has like 6 different caps but none *freaking* fit the E30 res. God dam it. You'd think a kit specifically for BMW's made by a BMW shop would have a cap for a fairly common BMW. But no, why would that make sense?
But one of the caps kiiind of fit; correct diameter, but wrong thread pitch. I used that and bled it again after replacing those items. Seemed to be fine. Saw a little water from behind the head. Guess I didn't replace that correctly?

I have pics,

One my way to work after the temp stabilizes:



I get my exact temp reading from the ECU with an OBD2 scanner: (the dangling wire is my manual fan switch)



The new reservoir looks like the old one: covered in coolant.





I have also noticed some debris in the res, and when I've drained the radiator. Small specs of.. stuff.





The latest theory: The head gasket might be head and/or the head has warped. Could be leaking combustion/exhaust into the coolant. Just throwing out any last ideas here.

Oh, and the pinging is getting worse. Pings bad only under load, for the first 15 minutes, then tame pinging for the rest of the journey.

[Panici]

Have you changed the water pump out? It seems you've addressed everything else.

May also be worth installing a VDO water temp gauge so you have a second (and analog) source of data.
This was the first aftermarket gauge I installed in my E30 way back when it had the original M20 engine.

It's easy to see when the thermostat opens, electric fan kicks on, etc:

https://www.youtube.com/watch?v=mVZE4X-OhKg

[moatilliatta]

Try a stock clutch fan?

[Chilezen]

Update, I replaced the thermostat with an 80° unit.

It seemed to bleed fine.

But it still has the overheating problem. I get on the freeway after about 5 minutes and then it overheats, but not as bad as before. It goes up to 110° but didn't stay there when I pulled off.

The lower rad hose was warm but not hot.

After sitting, it cooled to 88°, stayed steady in the 90s, but crawled up to 103 by the end of the drive (about half an hour).

Any ideas?