95 E36 M3 S50 HPDE Car Build Journal

[95maxrider]

Here’s a really shaky video of my new PB by 3 seconds! I’m sure the new motor helped but Nankang AR-1s definitely helped! Ran them at 31psi hot for max grip!

https://m.youtube.com/watch?v=rAWf_5lCEhE

Anyways, problem! Not sure if it was because I shut off the car on pit lane after a hot hot lap to check pressures... or something worse.

My new euro coolant tank spewed coolant out of the cap. When I opened hood, about an inch of coolant was low in the tank. I could hear air still leaking out of the cap.

Autometer gauge showed 190F and the dummy gauge was till dead center.

Bad cap? Blown head gasket?

This was my second track day. First track day had several 2:27 with no coolant loss.

Got that sinking feeling. I’m really hoping it was because I shut the car down to check tire pressures without any sort of cool down. Cap is 2 year old aftermarket Rein 2.0bar.

Full pace turn 17, pit in at turn 18, 1/2 mile until full stop and shutdown. Then I went back for another 3 laps before pulling into garage and a little puff of steam was coming out of hood vent.

Will a leak down show a bad head gasket? If I see bubbles in coolant tank that’s it right?

Oof, that's scary. With that fresh rebuild I can't imagine why the HG would go bad like that. I believe the best (easiest?) way to test for a bad HG is to buy one of those combustion gas test kits for the coolant. I bought one when I was thinking my HG was bad and it was simple to use, something like this. Coolant temps do spike by about 10* from what I've seen after shutting down the engine, and probably more if you were just running at WOT for a while and didn't do any cool down. But still, if you were running at 190, and spiked to 210, that's well below where the cap should vent. It could be as simple as a bad cap. I only run OEM at this point just to eliminate that as option (as much as one can).

[aeronaut]

That's a healthy run!! I'm good friends with the CI of the National Corvette club that runs a few events there every year, so maybe I'll make it there this year.

Head gasket....I've decided that the most reliable sign of a failed head gasket, is a fair amount of pressure in the system after complete cool down.

Unfortunately, you can have a blown head gasket and have a perfectly legit leak down and no bubbles. If those fail, you have a VERY blown head gasket.

[bimmerboy318]

That's a healthy run!! I'm good friends with the CI of the National Corvette club that runs a few events there every year, so maybe I'll make it there this year.

Head gasket....I've decided that the most reliable sign of a failed head gasket, is a fair amount of pressure in the system after complete cool down.

Unfortunately, you can have a blown head gasket and have a perfectly legit leak down and no bubbles. If those fail, you have a VERY blown head gasket.

I’m going to try a new BMW cap and try again. If it pops... I think that spells the end.

Hoping Scotch chimes in with the reason for his multiple head gasket failures he mentioned one season.

My wife is instructing at the next “NCM Bash” and I’ve registered for advance. Give me a shout if you ever come to the track!

[aeronaut]

Will definitely reach out if I make it there! I have family in Louisville, so it's an easy stay once I get close.

[skrimshaw90]

I would do a sniff test. Sure fire to know if combustion games are making their way into the cooling system.

[olemiss540]

If it was the head gasket you would still have positive pressure (hard hoses) after the car cooled down so check your hoses next time. I am guessing it's the rein brand cap. Try another brand cap IMO and congrats on the PB. Any other thoughts on the AR1s? Compared to others?

[bimmerboy318]

I’ve got a combustion leak tester and liquid. Also rented the cooling system pressure test kit. And I bought a new BMW cap.

Based on all I’ve read, the cap might not be the issue... might be an air pocket. The reason it could be air is that once I saw the coolant leak, and before the engine was fully cooled, opening the cap made the coolant rise... as if there was compressed air inside. Hoping that because there is no bleed procedure for the euro tank, I should have opened this cap as the engine warmed as a method to bleed... I didn’t. Just filled, capped and ran. 18miles on dyno, 75 miles track day 1, and on track day 2 along with PB, it expelled coolant. Thinking back that is the hottest the motor has ever gotten 190ish.

AR-1s? Run them 30-32 hot like a true race tire. The will take a lot of slip and keep gripping. They will also make a little bit of noise under slip. They don’t communicate like RE71Rs... they are there if you push. Haven’t past their limit yet to see what happens after that.

[95maxrider]

I’ve got a combustion leak tester and liquid. Also rented the cooling system pressure test kit. And I bought a new BMW cap.

Based on all I’ve read, the cap might not be the issue... might be an air pocket. The reason it could be air is that once I saw the coolant leak, and before the engine was fully cooled, opening the cap made the coolant rise... as if there was compressed air inside. Hoping that because there is no bleed procedure for the euro tank, I should have opened this cap as the engine warmed as a method to bleed... I didn’t. Just filled, capped and ran. 18miles on dyno, 75 miles track day 1, and on track day 2 along with PB, it expelled coolant. Thinking back that is the hottest the motor has ever gotten 190ish.

AR-1s? Run them 30-32 hot like a true race tire. The will take a lot of slip and keep gripping. They will also make a little bit of noise under slip. They don’t communicate like RE71Rs... they are there if you push. Haven’t past their limit yet to see what happens after that.

I didn't want to mention my extended problems with my coolant system staying pressurized long after the car had cooled since I didn't think it was relevant with your euro cooling system. But I had the exact same issue, where I would open my cap after letting the car sit for days, and I would always get a geyser of coolant. That's what led me to get the combustion gas tester kit. But it always came back negative. I eventually found the culprit, and it was like you suspect, an air pocket in the system. To get rid of them once and for all, I combined all the best coolant burping how-tos into one document that I now follow every time I change coolant, and have not had an air pocket since. Here's what I do:

Drain the engine block first. The drain plug on the block is 19mm. Need crow's foot wrench on short 3/8" extension. Tighten to 18 ft-lbs. Then drain radiator and tighten to 23 in-lbs. Use new crush gaskets for both. Mix 50/50, capacity is 2.8 gallons.

1. Put front of car up on ramps about 12".

2. Set interior fan to max speed and heat (with the engine off). Make sure center dash vent is set to heat.


3. Remove bleed screw and expansion tank cap, and add coolant very slowly to the block through the upper radiator hose until full, then flip hose around and fill radiator directly.

4. Once the block and radiator are full, fill up the expansion tank until only coolant, no air bubbles (keep pouring....more air bubbles will likely keep coming out) come out of the bleeder screw location. Squeeze both radiator hoses. If the level drops in tank, refill until no bubbles come out of the bleeder screw, and repeat until the level doesn't drop after squeezing hoses. Reinstall bleeder screw. Keep main cap off.


5. Turn the engine on, heat and fan still at max.

6. When coolant temp (via OBD2 port and Torque app on my phone) reaches about 150*, slowly rev engine to 3,000-4,000 rpm for 10-20 seconds. Then crack the bleed screw until no more air bubbles come out. Do not add more coolant to system during burping procedure. Repeat revving once or twice. Tighten bleed screw to 18 in-lbs.

7. Check upper and lower radiator hoses for heat. When the lower hose gets hot, that verifies that the thermostat is working.

8. Verify heat in the cabin.


9. Check expansion tank for flow for proof that the water pump flow is strong.

10. Usually make sure electric fan kicks on (about 205*)


11. Take the car for a quick, hard drive and then park it. The following day top off the expansion tank if needed. Then open the bleed screw to let any air out. Do this a few times, in this order, until the level in the tank stabilizes and/or no more air comes out of the bleed screw. This step must be done with the engine/coolant at ambient temperature.


The thing that really did it for me was revving the engine to 3000-4000 rpm and holding it there for a while. 2000 rpm just didn't do it for me. Good luck, and keep us posted!

[bimmerboy318]

Great news! Combustion leak test was negative! I still think it was the cap all along. Even at idle and shutting off the car at "operating temp" per the dummy guage, the cap would hiss. The new BMW cap doesn't. I also researched how to bleed an E30... which uses the same reservoir. The E30s have a bleed screw, I no longer do. So I ran the car up to temp with the cap off as a way to exhaust the air.

I also changed the oil to Redline 10w40 and hooked up the Accusump! Car takes 10 quarts now. Also the electronic valve Accusump works better than I thought. There is no need to turn it on for it to fill. It will fill but not release the oil unless it's on. Was able to get 64psi according to the guage. When starting the car, pressure goes from 64 to 40 before the car actually starts and oil pressure goes back up.

2F1E1BE1-9B65-4CC9-8D50-7442ECD280CD by D S, on Flickr

[bimmerboy318]

Still blowing out cooling with new cap.

I can go out and run 2:30sec laps and all is well. As soon as I push to 2:27sec and below... the dummy gauge starts to go up and I slow down. And the dummy gauge goes back down.

The weird thing is that the autometer gauge never goes past 180ish.

Someone suggested the thermostat might not be opening all the way? So at slower speeds 2:30 sec lap times, the tstat is open enough to keep it cool, but at faster laps 2:27 and faster, the coolant blows out the cap.

Any other suggestions?

[95maxrider]

Still blowing out cooling with new cap.

I can go out and run 2:30sec laps and all is well. As soon as I push to 2:27sec and below... the dummy gauge starts to go up and I slow down. And the dummy gauge goes back down.

The weird thing is that the autometer gauge never goes past 180ish.

Someone suggested the thermostat might not be opening all the way? So at slower speeds 2:30 sec lap times, the tstat is open enough to keep it cool, but at faster laps 2:27 and faster, the coolant blows out the cap.

Any other suggestions?

I use an OBD2 Bluetooth dongle in combination with the Torque app on my phone to monitor coolant temps. Where is your Autometer sender located? IIRC the dummy gauge will stay in the middle up to at least 210*, so if you're seeing the dummy gauge rise above that, you're probably getting to 220* or more. I would trust that over the Autometer at the moment. Having a third source, like the Torque app is worth the cost of the BT dongle.

Did you ever attempt to burp the system when installing the OEM cap? If not, I would do that. Your symptoms indicate air in the system.

You can also remove the thermostat and test it in a pot of boiling water and make sure it opens up at 195* (if you're running stock temperature). To aid in burping my system, I drilled a tiny hole at the top of the thermostat.



Are you sure your fans are kicking on at the right temp? Again, the Torque app is your best friend for this.

[fbirch]

As mentioned above, your Autometer temp gauge might not be reading high because of where it's located. I had a very tiny leak in my HG and got the same symptoms as you: dummy gauge would start to climb but Autometer gauge (who's sender was on the cold side of the radiator) didn't show anything wrong. After replacing the head gasket, I moved the sender to middle of the top radiator hose, by installing an inline hose coupler with a port for the sender. It comes up to temp much more quickly than before and shows the true dynamics of water temp. By the time the OEM gauge starts moving away from mid span, you are on the brink of being way too hot.

[bimmerboy318]

Ok, bad news, head gasket is shot. Water was collecting in cyl 5. Sparks plugs in all looked like they were steam cleaned.

The end was getting nearer as symtoms were worsening. We used a vacuum Airlift coolant bleeder/filler... it took 1/2 gal of coolant mix and we thought we were on to something. Well, took it out for a spin. And the needle started to rise at the end of the front straight. But this time, the needle didn't come back down, instead it kept climbing until the light turned on.

Pretty sure there was a small leak. Then after all my antics trying to bleed and playing russian roulette with the temp needle, it kicked the bucket.

Hopefully this head isn't warped into a rainbow. I'll have my engine builder check it and pressure test it. But since my local pull a part has 2 400 casting heads on cars... I'll be pulling both as spares in the next week or so. Bummer. Car was destined to go sub 2:20 at NCM.


Also planning to delete the thermostat completely, drill and tap the tstat housing for the sending unit.

Anyone think I need to upgrade the head gasket to a cut ring?

[olemiss540]

ARP head studs are awesome in case not already installed. No need for a cutring IMO but I am not very well versed in them. I went back with a stock style gasket and studs for better clamping force/distribution.