[e90pilot]

While I haven't had any problems during regular driving, on the track my car vents A LOT of coolant then cuts power as it starts to overheat. The funny part is the water temp display shows about 80C which I thought was pretty normal. Eventually the car stopped accelerating and I got the yellow over-temp warning followed by low coolant. I let the car cool off during lunch and opened the filler cap. Quite a bit of air came out and I had to add almost a half gallon of coolant throughout the day. Other than that there are no stored codes or shadow codes.

The problem with this is the fact that I can only replicate the issue on the track which makes it difficult for a shop to troubleshoot. My theory is that if there is a hole in the head gasket, it really doesn't open up until it sees high cylinder head temps. Does anyone have any idea on how a shop could replicate this? Maybe it's not a blown gasket but a simply a trapped air the needs to be flushed. I'm guessing the only was to know for sure is a compression check. What do you guys think?

[F32Fleet]

Could be a hole in radiator. I waited 2yrs to get a pin hole leak repaired on my e90 330. Check under oil cap for coolant mixed with oil if you think its a head gasket.

[e90pilot]

Interesting. I don't see any evidence of leaking on the radiator though. There're marks all over the reservoir and cap.

[Bartman619]

Any coolant leaks under the car? Any white smoke out of the tailpipe ? Any coolant smell inside the car interior coming from the A/C vents ? Try a new radiator reservoir cap maybe.

[e90pilot]

I couldn't really see if anything was coming out of the tail pipe but that though go me thinking. There are some soot stains on the outside of the tips that were not there before. I'll grab a pic later to show you. Coolant was leaking on the ground but that was for sure conning from the reservoir as the puddle was right underneath. Also, it slashed on the headers and made a lot of smoke. The a/c and fan was off so I can really confirm if any coolant was coming from there. I could definitely smell the coolant as I had the windows down and the reservoir is right next to the passenger window. I also had the system pressure tested not that long ago. Pressure held just fine

[e90pilot]

Shop says its a warped head... Not good.

[Bartman619]

not good...i'd check salvage yards for a good used e90 325i head and have a competent indy shop/indy BMW garage do the install. Did the engine overheat ? Just asking because usually that's when the hear warps.

[e90pilot]

I got the yellow over temp warning only. If the head is warped isn't the block warped too?

[Bartman619]

Yeah..it could be also. The machine shop will have to mill the block. Be sure they do a proper leak down test also. I went through this entire ordeal with my e36. Also while the head is out, might as well have the valves, valve springs, and all associated gear with head. Have them checked and only replace if needed.

[e90pilot]

It's funny though. I can only replicate the problem on the track. Also the car seems to vent coolant then overheat. I think the the high engine temps are a result of blowing coolant overboard. What if it's as stupid as f reservoir cap as someone mentioned?

[Bartman619]

Originally Posted by e90pilot

It's funny though. I can only replicate the problem on the track. Also the car seems to vent coolant then overheat. I think the the high engine temps are a result of blowing coolant overboard. What if it's as stupid as f reservoir cap as someone mentioned?

Yes it could have been the cap. On my e36 the previous owner never changed the coolant. As a result it corroded the aluminum heads via electrolysis. $3400 later I had head rebuilt and the engine was good for another 150K. Hoping for the best in your situation. Keep us posted on your car's status.

[F32Fleet]

Look through oil cap. If you see mayonnaise goop you'll know its a bad gasket.

[e90pilot]

Originally Posted by Socom

Look through oil cap. If you see mayonnaise goop you'll know its a bad gasket.

Look clean. So does the coolant. Gonna get the coolant flushed tomorrow and see.

[rusty_g80]

It is most likely a faulty water pump. Not a cheap fix either but way better then head gasket. How many miles are on the car? Water pump fails at about 60k on average in our cars. My car was overheating and had similar symptoms to yours. Even closer to your case...I had one of the members on this board pm me and he had almost exact issues as you, the car would only overheat when driven hard. Do you hear any noise when it happens (like rattling)? When the electric water pump fails in our cars it sometimes is weird as the car would be fine if you drive it gently with heater off, but driven hard or with the heater on the pump just cannot keep proper flow. BTW I would suggest replacint the tstat while you at it. DO NOT BUY A USED WATER PUMP my old pump looked fine and even worked to an extent :-).

[rusty_g80]

BTW you can get a pump for about $400 or less and tstat for $95, BMW coolant should be about $20. I suggest BMW coolant and it will cost you the same as premixed Prestone as you only need a gallon of coolant and a gallon of discilled water. If you do it yourselt it will take 4 to 8 hours depending on your skills and tools. Takes longer for XI because of front subframe that's in the way.

[e90pilot]

I need to know for sure though. I'm already running an updated pump. No shadow codes have been stored. No rattling either.

[rusty_g80]

When was the pump replaced? Since you're not seeing any oil mixing with coolant I would not rush to change the head gasket. Do a leak down test (not compression test) and see whot it shows?

[e90pilot]

That's gonna be next on the list. Also the water pump thing got me thinking. What if it's starting to go as you say, but not enough to actually throw a low flow/low rpm code? It has to reach a threshold before the car throws the code. Most people find out when street driving. The pump could have been bad long before. I've got a BT tool and a track day coming up. Maybe I can view the actual values and try and see if anything looks funny.

[rusty_g80]

When my pump went bad it threw no code. At least I couldn't get it with BT scanner and the dealer did not mention anything when they scanned the car about a month after I replaced the pump. Head gasket is a costly fix unless you do it yourself, so I would run all test possible before doing a head gasket replacement.

[e90pilot]

Originally Posted by rusty_g80

When my pump went bad it threw no code. At least I couldn't get it with BT scanner and the dealer did not mention anything when they scanned the car about a month after I replaced the pump. Head gasket is a costly fix unless you do it yourself, so I would run all test possible before doing a head gasket replacement.

I think you're right on this one. Just went to the track and ran the heater full blast. It took much longer to overheat. Before I do anything though I really need to make sure. The BT tool can tell my current water pump electrical load and rpm. Now all I need to know is what it should be at on the track. Running the heater in Monterey in the winter works out ok. Not so much at Thunder Hill in the summer.