Alu M52 Overheating --- Update: Sill having issues

[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]

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.

[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.

[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.

[Chilezen]

Small update,

I had taken a break from using or working on my car. Then I took it in to work on Friday, with the plan to rent a leak down tester that night. Lo and behold, the auto stores nearby don't have one.

But it wasn't a wasted trip; I learned two other things.
I asked my boss to sit in the car as we went around the block. When he heard the pinging sound, he thought it sounded like an exhaust leak! Crazy, I never would have thought. But he's not sure of course, he just said it doesn't sound like pinging.

Then on the way home, my commute on the freeway includes going up a large grade. The car's temp rises as I push it, which makes sense, so I decided to push it harder and speed up the hill.

Of course, it starts to overheat (120°+), so I turned on my heater full blast. The heater was cold. The car was overheating and I had no heat circulating through the core! Never noticed this before! I drop the gears into neutral and coast for a bit, and the temp falls back to normal, and then I get the heat back through the vents. This test is easily repeatable.

Yes, the hoses are routed correctly, with the cylinder head going to the bottom metal pipe, and the top metal pipe goes to the metal spider hose to the front of the engine.

So, why would I lose heat in the cabin when the engine gets hot?

I do want to do a leak down test but I have to buy my own tester first.

[gazellebeigem3]

You lose heat from the core because its full of air/ empty of coolant however you want to look at it. You need to find out where the coolant is going. Have you done compression test? A compression test also does not require shop air. Finally, that's not pinging to my ear.

[Chilezen]

Weekly update, since I only drive the car once a week now,

Bought a Harbor Freight Leak Down Tester. Performed the test on a warm engine, just right before operating temp (80C) Listened and inspected carefully. Results:

Input pressure, 80psi
Cyl 1- 76
Cyl 2- 73
Cyl 3- 74
Cyl 4- 75
Cyl 5- 76
Cyl 6- 78

That's reasonable. All leakage I heard was through the oil cap/oil dipstick. The lower numbers (2 & 3) were a tad louder, same place. Never saw bubbles in the coolant reservoir. Definitely isn't blown between cylinders.

That's good news.

Bad news I'm essentially no closer to finding the root cause of the problem.

Next best guess is a lazy water pump. Since it overheats so quickly, I'm thinking water isn't circulating fast enough. Hell, there could be a blockage. All I know is it leaks bad.

Yes, there could STILL be a huge air bubble in the heater core. I'll look into buying my own coolant vacuum bleeder.


And I've made no progress on fixing the VANOS (still has a bad idle and a code) and no progress in identifying the knocking sound.

[mtech325]

Not sure if it has been tried, but something that may help with bleeding air from the system is to fill the radiator through the top hose first. At least with my e30s and e36 over the years, I've had better results than just filling the tank. Sounds like your car is OBD2, so you may have the metal water pipe instead of the rubber spider hose, but another problem I ran into was the heater core hoses getting pinched under the intake manifold since I was in a rush to get everything installed. Albeit I use the 88 degree t-stat, switching to the s54 z3 radiator made a noticeable difference in cooling for around town and freeway driving over the standard late model e30/e36 radiator, but the downside is access to the front of the motor is more cramped for things like belt changes and alternator replacement.

[2mAn]

Wasnt there some progress this weekend?? Spill the beans man! lol

[Chilezen]

This weekend...

On Saturday, I began replacing the rear cylinder-head-to-flange (to heater hose) gasket. This time, instead of using another Genuine BMW gasket like I did the first time, I used a Permatex "water pump & thermostat silicone" RTV. I cleaned up the area, applied it, waited an hour for it to cure, then tightened it (following the instructions). I had to wait 24 hours for it to set before refilling the system.

I also did one other thing: Backstory is, my cylinder head had 2 ports on the side, one for the temp sensor, and one for that coolant line that goes to the throttle body. I took out that line and installed the brown temp sensor for my cluster.
But because I plan to pass BAR with this engine, I needed to have a functional throttle body line. So I bought & built a Tee fitting and spliced it into the coolant line going from the cylinder head to the heater. I cut the line in half, slipped the Tee in, and then fed the throttle body from that point.
I figured, this works just the same as if the line was coming out from the side of the block, only instead it comes from the back of the block.

I removed my Tee fitting and simply installed a coupler, so it's just a hose, as it was originally. And then I plugged the other end.

What changed?

Nothing.

Almost absolutely nothing changed.

What did change, was that I noticed the leak I saw previously isn't coming from that flange.
No, there's a small leak that starts from right under the cylinder head. But it's so small that it stopped leaking when the engine warmed up. Seen here:



See how the water drips a little left of the flange? I couldn't get a better photo, but it looked to me like that's from the head gasket.

There was otherwise still no difference in how the car drove: the car still overheats, and the heater blows cold air sometimes.

Some other pics:


This BMW gasket had this extra layer of blue-something. I didn't know which way it was supposed to be oriented, since it fit both ways. I'm pretty sure I faced it towards the head. It doesn't seem like it was leaking.



One extra important bit of information: Every time I drain the coolant, there's always debris. This is metal flakes mostly, and some tan bits of, something. Yes, there appears to be a thread shaving on the left. And a bit of black gasket stuff (?) next to it. This is exclusively drained from the radiator, and I cleaned the pan prior to filling.

[Chilezen]

On Tuesday...

First sidenote: the hoses definitely aren't getting pinched. The bends are smooth.

To improve the thoroughness of the bleeding, I bought the vacuum bleeder kit. So I drove the car to my shop, which it did fine (relatively). It didn't loose a bunch of coolant like it has before. So that's an improvement. I don't know if that's because the gasket I replaced did leak, or some other unknown factor didn't cause a massive piss during the 45-minute drive. Coolant was low and definitely sprayed out from under the reservoir cap, as usual.

At the shop:



Drained the coolant, this time from the radiator and the block. Wow that sucks so much. My other car is a first gen Toyota Tacoma, and on the block, it has a little fitting for you to pop on a hose, and then you crack a bolt, so you can drain the block very neatly through the hose. I want one for this stupid motor :(

Once again, there was debris in the coolant. I wanted to reuse the coolant so I filtered it through some new shop rags. Then I added more fresh mix to the bucket, and began the process.



It held vacuum for the 5 minutes I waited.

No leaks. No hissing. That needle stayed put for the longest 5 minutes ever. The system is tight. The engine was warm too. I drove it for 10 minutes prior to emptying it. No of course it wasn't hot, I'm not that much of an idiot.

Just to be clear, no leaks.

So I opened the tap and filled'er up. Worked perfectly.

I started the car, jiggled the hoses a bit, and all seemed fine.

Cleaned up, drove home.

Overheated as soon as I got on the freeway. And again, no heat blowing through the heater only when that happens.

I took the freeway exit, stopped for less than a second, drove straight, and got back on the freeway, watched the temp drop, and kept going.

I dropped from 107 to 90C in less than a minute. The thermostat opened, yay!

It does this every single time. The engine heats up faster than the thermostat will open.

And then I drove home, while the temp slowly crawled up again, from 90 to 101 by the time I got home.



Not that you really needed proof but there it is. I did loose a bit of fluid again, again from the res cap. (It's a new cap and reservoir, both twice replaced. Can't imagine both have been bad each time.)

I bled the shiz out of this. There should be no reason an air bubble is still causing this.

---

There's only three other things I can think of:

• A bad water pump (which doesn't make sense because I've driven to work and home... I would think a bad pump would never let me get more than 10 minutes from my house... but it would explain why the thermostat opens late, due to lack of circulation), or,
• I really do have combustion leaking into the coolant (that the other tests have not caught) causing air bubbles, or,
• the engine is running insanely lean? Is that possible without throwing a code or showing any other signs?

I do need to find out soon because summer is coming and I intend to reinstall the A/C on this car...

[moatilliatta]

I chased my tail on an M20 for a few months till I put a head on it. And have watched others chase there tail on M5X engines with a cracked head.

I would look at the head gasket, and if it looks find, look at putting a head on it.

It probably pushes combustion though at a certain temp and load that cant be replicated in the shop.

[Northern]

I wonder if the metal shavings in the coolant are from machine work? If not, it basically *has* to be from the pump?

Did you pull the pump when you had the coolant out? Hopefully the Oring seal means you'd be fine to R/R.

If you're running crazy lean, I think the long term trims are +/- 28% max. It throws a code if it hits those, which is a lot of fuel.
Should be able to see LTFTs or "Lambda Multiplicative" with a scanner, INPA, romraider logger, etc.
If your bank1/2 O2 sensors are switched, it'll usually pull fuel on one and add on the other until it hits the limit and throws a code, but since it hasn't done that, I don't think that's the case?

I'm wondering if the pump ate itself, or tstat somehow doesn't open fully? Both are a hell of a lot cheaper than pulling the head.

[Chilezen]

I wonder if the metal shavings in the coolant are from machine work? If not, it basically *has* to be from the pump?

Did you pull the pump when you had the coolant out? Hopefully the Oring seal means you'd be fine to R/R.

If you're running crazy lean, I think the long term trims are +/- 28% max. It throws a code if it hits those, which is a lot of fuel.
Should be able to see LTFTs or "Lambda Multiplicative" with a scanner, INPA, romraider logger, etc.
If your bank1/2 O2 sensors are switched, it'll usually pull fuel on one and add on the other until it hits the limit and throws a code, but since it hasn't done that, I don't think that's the case?

I'm wondering if the pump ate itself, or tstat somehow doesn't open fully? Both are a hell of a lot cheaper than pulling the head.

I don't think the metal shavings wold be from machine work anymore, because I've drained the coolant 4 times now, and each time the shavings have been there. It's possible, but unlikely. The pump could be eating itself.

I did not pull the pump because 1) my method has been to do one thing at a time, so I can pinpoint the cause. I don't have a problem opening up the system multiple times diagnose. And 2) I want to buy a pump to have on hand to install, if the pump does need to be replaced. I haven't bought one yet because I have been hoping to have found the problem already.

I'm going to assume the "Scan Gauge 2" unit I have plugged in doesn't read LTFTs. What is an INPA?

On the Z3 engine, from the factory, there's only 1 pre-cat O2 sensor, located at the Y-merge before the single cat. The headers are plugged. This does give me the opportunity to install something like a wideband on each bank if I wanted to, but I haven't looked into it. So considering it's set up from the factory like that, and I am using the ECU that came with the engine, I can't suspect there is a fault there.

I was talking to someone at a car meet, and he pointed out the possibility of the wrong head gasket, restricting flow from the block to the head. I highly doubt the engine builder would have made that mistake, but hey, after all this, there's a chance.

Thanks for the suggestions. I think I will buy a water pump and tackle that next. The metal shavings point to a fault there.

[Northern]

INPA is BMW's diagnostic reader/live data viewer from the OBD2 era, multiple versions have leaked over the years along with other factory tools for flashing/coding.
It can be a pain to set up, but I mention it because it's free and works well once it's setup.
On the other hand, romraider logger is also free and would be easier to setup if you use the MS41 ECU portal (here: https://sites.google.com/site/openms41/romraider) that basically automates the install/setup.

But yeah, I forgot you had a Z3 harness. Can absolutely do the wideband, MAP, etc, to the pre-cat Bank 2 sensor, or the post-cat Bank 2 if refresh rate is less important. I'm told there's nothing different about the Z3 DME hardware so it's doable.