Alu M52 Overheating --- Update: Sill having issues

[Chilezen]

When I had bleed the system in my driveway, I had felt all the hoses as it got up to temp.
But this morning, on my way to work, the temp spiked and I pulled over--I grabbed the lower rad hose like you said and it was cold! Freakin fantastic. I waited there, the temp dropped, and then I drove away. The temp stayed around 96. I pulled over again, checked the lower hose, and it was hot.
So I need to find out what thermostat is in there and install a lower one.

The leak from the reservoir comes from between the cap and the reservoir. It does also expel water through the vent hose, which I have routed into the driver wheel well. It's definitely spilling down there.

I do still loose fluid and it's hard to keep track of where, so I can't track if it is building pressure properly.

So for now, my solution is to find a lower temp thermostat, replace the reservoir, and maybe the gasket at the back.

The fan is blowing into the engine bay, yes.

Yes, the block was time-certed.

About getting a tune- I am planning to CA BAR this car, so I'm assuming I shouldn't have a tune if I want to pass emissions. Although it might make sense to have a correct "S50" tune that can pass emissions... I really don't know, I'd have to ask tuners and judge what I can afford based on if it's necessary. That sort of makes sense.

The wiring harness was done by a member on here; I sent it to him, he re-pinned the C101, and labeled everything. He knows my goals and I assume he configured everything correctly for me.

Yes, I'll check the O2 wiring soon. When I cleared the codes earlier for the cam timing, it cleared them all. Only the cam code has come back. Time will tell.

At least now I have more to discuss with my engine builder, he'll be able to tell me what thermostat is in there.
Oh and he rebuilt the engine but I did all the work to swap it. So he wouldn't be at fault for not going the extra mile on that front.

Thanks guys!

[moatilliatta]

Is the fan blowing the correct direction? Have you tried just running a clutch fan?

Did the shop time cert the block?

P1519 - My guess the Vanos doesn't have 8.5MM of travel

P0135, P0141 Id check your 02 wiring and trace it back to the DME and check its pin out to make sure its wired like the configuration you want it.
I've only done STD E36 harness with 4 o2 plugs, deleting rear 02's.

A lot of shops don't go the extra mile to make sure everything is right, In retrospect they don't charge all that extra time either. I've put in my share of hours on cars at the shop to make sure everything is proper.

[mjweimer]

Is the lower radiator hose hot when you are experiencing the overheating issue? If the thermostat is stuck closed the lower radiator hose will be much cooler and you will see higher temps. This doesn't explain why it would be OK after you stop and continue on unless the t-stat opens during that time where it is sitting.

You say the radiator cap is leaking...is it leaking around the cap itself or from the small overflow tube (the overflow tube is to the right of the fitting where the small hose connects to the upper radiator)? If it leaking from the overflow tube that implies the cap is lifting due to pressure, if it is leaking around the cap, the cap is either bad or the reservoir is warped/damaged not allowing a seal. Is the cooling system building pressure even with the small leaks?

Bummer about the leak on the back of the head, that gasket will be a bear to change in the tight engine bay.

Lot's of directions you can go from here depending on your answers.


You should look into a tune for the new cams, the engine would run with a stock tune but it won't be optimized for the set-up. The vanos timing may be off, so that should be checked with the proper tools to hold the cams/flywheel at TDC. If you are hearing pinging, it could be partially the result of the tune, cam timing, poor spray pattern from the injectors, etc. etc.

I'm not sure what to think about the O2 sensor issue, most of the threads seem to be dealing with OBD1 cars. Are you experiencing any dirveability issues? Since you are running pre and post cat sensors, I would make sure the wiring is not switched between them - front to back/back to front before going further with any kind of fix. My OBD2 swap M52 has the post cat sensor deleted in the tune with no codes and smooth power delivery.


These swaps are never straightforward because each set-up is just a little bit different. It takes some time to get it sorted but keep chipping away at it.

[Chilezen]

This swap just hasn't been smooth sailing at all for me...

The first issue I'm having now is that despite how thorough I bleed the cooling system, the car still boils over. Here's the setup:
Freshly rebuilt Aluminum M52 by a reputable BMW shop
OEM/Behr E36 Radiator
Custom mount to move the bottom mounts forward, increasing space for an electric fan/motor
Flex-a-lite Flex-Wave Puller Fan: 16" rated for 3,000CFM
Custom mounts to fasten the fan directly on the radiator
80/88° Radiator Temp switch
I don't know what degree thermostat
2.0 Bar Reservoir Cap
Zerex G-05 coolant + water, unknown ratio at this point.
Everything else, stock
No AC or aux/pusher fan
Ambient temperature has been between 50-75°F.

Since I'm running OBD2, I have a scanner hooked up to read the temp at all times.
My method to bleed it has been to put the front of the car on jackstands, and run the engine, revving every so often, and squishing the hoses. I've witnessed bubbles continuing to appear well after 20 minutes of revving and squishing and refilling. The car's temp had stabilized at about 96°C.

This is my daily, so I drive it to work. It takes a few minutes to get on the freeway, at which point the temp has almost come up to 90°. Once I get on the freeway, whether it's morning/afternoon/night, I have to pull off again. The temp almost immediately shoots up into the 110's. So I'll get off the freeway and pull over, and the temp immediately falls as I park. I'll wait there for a couple minutes, check the water level, which is usually now between an half to a quarter, and then I'll get back on the freeway. Here's the crazy part: the temp is stable for the rest of the journey! It sits around 94-98° for the rest of the drive, whether or not it's on the freeway or around town.

It drives me nuts. Sometimes I've refilled the reservoir right when I pull over, and sometimes I don't, and I'll do it in a few hours. Yes, I have taken the cap off slowly while it's hot, only for steam to come out because the level is very low. I would refill it and just keep going.
I've noticed leaks everywhere. I've tighten the clamps everywhere, so now it's leaking from just two spots: the Reservoir Cap, and the junction at the back of the head, where the heater hose connects (it leaks between the head and that junction, at the gasket). I've also noticed a bit of water from the heater box drain tube, that drains on top of the transmission. I took apart my center console to learn when fluid comes out of that drain tube, and it was inconclusive; water came out in such a small amount that I couldn't determine it was really a leak.

It's crazy that it will overheat in the first 10 minutes of driving, and then be fine for the next 20+. It only does it at the beginning, so I pull over, wait, and then continue like normal.

Other observations: I checked all the spark plugs. They look fine (I took pictures too). I checked the oil. The level was a bit high, so I though Oh crap, there might be water in the pan. So I drained about a cup's worth of oil: it looked fine. I did an oil change about 400 miles ago, so it was still somewhat clear. I didn't see any water come out, so I guess I just put a little too much oil in last time.

The next issue is about the codes: P1519, P0135, P0141.
P1519 is an error in the cam timing. It suggests I need to retime the cams. Another source suggested the issue lies with the Vanos solenoid. I replaced that with a used unit, cleared the code, and the code came back.
The symptom of the code can be a rough idle, loss of power, and poor fuel economy. But since this swap is new to me, I don't know what the baseline is for correct power and economy. I do however have a rough idle. I thought it was due to the engine mounts, because it shakes pretty bad. But it goes right away as soon as I rev.
The Vanos was rebuilt by me using the Beisan Systems rebuild kit. I followed the instructions, and when I was done, I gave it to the engine builder who installed it.
It's worth mentioning that I have S50 cams, so maybe, since there's no tune on this stock ECU, maybe I'm getting the code because the cams are ground differently. Is that a concern that the ECU would catch?

The next two codes are for the two O2 sensors. Since I'm using a Z3 engine, I have a Z3 harness and ECU, which uses only 1 upstream/pre-cat and 1 downstream/post-cat sensor. The codes are specifically for the heating elements. I searched (I always search before asking) for answers, and it led me to this rabbit hole of issues:
https://www.r3vlimited.com/board/for...v-backfeed-diy
https://www.r3vlimited.com/board/for...roblem?t=55208
https://www.r3vlimited.com/board/for...h-idle?t=74958
https://www.r3vlimited.com/board/for...ckfeed?t=80056
https://www.r3vlimited.com/board/for.../page2?t=76548

Basically, 24v swaps have been known to have this issue withe heating elements. There is a fix, but the exact issue still is a mystery. I haven't checked my car for the voltages like he instructs, and I haven't wired in the fix yet. I've been stuck with the first two^ problems so far. I did however check the wiring to the sensors, finding 12V / 4.5V / 4.2V / Ground in each of the looms, and both sensors gave me consistent continuity & resistance checks. I don't remember the exact values or wires.

But I do see some relationships discussed; the dysfunctional O2 elements produce similar symptoms as the faulty Vanos. I don't know/think there is any correlation, but it was interesting to find that in my case.

One of the scariest issues I'm witnessing is what I think is engine knocking. I can hear faint pings when the engine is coming up to temp, for about the first 10-15 minutes, during all levels of throttle input, and most notable around 3k rpm. I don't really know if what I'm hearing is pinging, but I do know the sound goes away after a while. But again, I checked the spark plugs, they're pretty clean. I'm running 91 gas from Shell. My exhaust is very black, though. I'd consider this amount of soot to be abnormal for a new engine.

Sorry for the wall of text. I'm just paranoid and terrified that my new engine is toast. I'm running out of time and patience and money. If I can fix anything, I really want to, but if I have to take it to a shop, I will. I haven't brought it back to the engine builder, because I want to give him enough information to work with first.

I've gone the extra mile to make sure almost everything is new and done correctly from the start, making this a lengthy and expensive project.
So it shouldn't be this damn hard to just swap and engine and enjoy the car, whereas others can do half the work and get a reliable beater.

Thanks!