Bleeding issues/overheat at idle issues

[BenM]

After doing my last track day at NHIS on July 5th I can't seem to get the cooling system properly bled. It was running into the red and slightly to the left of the red for some of the sessions, but had no issues running or mixing coolant/oil.

So last week I attempted to rebleed the cooling system in an effort to get it to run cooler. I was able to get it so that when I reved it up to 2500rpm no air bubbles/pockets would come out of the bleeder screw (just straight coolant), but once I brought the RPMs down to idle it would spew foamy water and then a ton of airbubbles. Bled it 5 times with the front end in the air and this happenned every time. Was able to get it so the car ran at 1/2-way when moving, but whenever I stopped even with the fan on, the temp gauge would creep up quickly past the 3/4 mark and even worse if I didn't have the heater on.

I'm hoping the head isn't cracked, but I guess its not out of the realm of possibilites. It seems like only at idle there is air being introduced in the cooling system, but I have no idea where. There are no coolant leaks either. Maybe a bad radiator cap or thermostat? Here are the specs of the swap:

M50TU
318is Radiator
88deg. Thermostat
SPAL 12" Pusher Fan
80/88deg. Fan Switch with stock wiring


Any ideas on what the issue could be?

Thanks,
Ben

[UNHCLL]

Ben,

Have you considered dropping in a lower temp thermo? 80*C?
I did that on my e36 M3 mutt, and it was a huge improvement on keeping the temps consistent, even when stopped in traffic with a marginal cooling fan setup.

-Chris

[M-technik-3]

As a basic I agree with Chris, it's cheap and also add a bottle or Water Wetter. What water pump is in the car? Not that this makes a huge difference if this is not happen on the street as well.

Was the humidity index up there that day?

Any noticeable loss in fluid? That would mean to me maybe a cracked water jacket in the cylinder head.

[BenM]

Ben,

Have you considered dropping in a lower temp thermo? 80*C?
I did that on my e36 M3 mutt, and it was a huge improvement on keeping the temps consistent, even when stopped in traffic with a marginal cooling fan setup.

-Chris

Chris,

I have a spare 75*C Thermostat waiting to go in, but was hoping I could get it to stay consistent with just the 88*F one. I'll swap it out today or tomorrow.

Thanks.

As a basic I agree with Chris, it's cheap and also add a bottle or Water Wetter. What water pump is in the car? Not that this makes a huge difference if this is not happen on the street as well.

Was the humidity index up there that day?

Any noticeable loss in fluid? That would mean to me maybe a cracked water jacket in the cylinder head.

I'll swap the thermostat and grab a bottle of water wetter. It's available at regular autoparts stores right? If not I'll just get if from Bavauto.

The water pump is a metal empeller graf unit, but I've heard mixed reviews on them and was considering upgrading to the stewart unit. Humidity was near 90% that day along with 95*F temps. It was fucking hot. No loss of fluid at all which has me stumped.

Thanks for the replies.

[jlevie]

It was running into the red and slightly to the left of the red for some of the sessions

A single trip into the red is all it takes to damage a head gasket. What you describe as happens during bleeding makes the possibility of a head or head gasket problem pretty likely.

[BenM]

I don't have a leakdown tester, but I'll be doing a compression test this afternoon and will let you know the results.

[BenM]

Haven't done a compression test yet, but I think the problem was combo of low coolant (durrrrr) and the use of tap water in my 50/50 mixture. I backfed through the top rad hose with distilled water, jacked the car up and was able to bleed it very successfully. Still runs a little hot for my taste as the needle is just to the right of the center and after a quick spurt of hard driving, the needle moved between the 1/2 and 3/4 mark and the fan quicked on high.

Will grab some water wetter asap and throw the 75*C thermostat in at some point soon.

[BonnschE30]

did you resolve this issue? I have the same symptoms with the same radiator, but I'm pretty sure my thermostat isn't opening. Hot upper radiator hose, cold lower...