[Dynomyte]

Hey guys I have been having issues with my engine oil temp for about a year now and I would like your help to solve this issue.

My car is a 2007 e92 335i manual with 107,000 kms. It is also FBO.

The story

I brought in my car last year after it overheated to get my water pump and T-stat replaced at the dealer. Ever since I got my car back, my oil temperature has not been the same. Usually when cruising oil temps are slightly below the half way mark (120C is the halfway mark 250F) and are reluctant to pass that mark. Since I got my car back my engine oil is at or above the halfway mark while cruising. If I do 1 or 2 pulls once the engine is hot, the oil temps will easily reach 130C. I never had that problem before. At that temperature the car makes much less power.

I brought it to the dealer as I suspected it was a faulty part they installed and they said everything was working fine (even though the foreman that did the road test said there was obviously a problem). They said that the water cooling system of the engine should not have an impact the oil temperature of the engine.

Now I am desperate to fix this problem as I am not enjoying my car anymore. I need your help to try to troubleshoot what could be causing this issue.

I have the following codes at the moment.
29F3 Fuel Pressure sensor
2C9F Lambda probe heating behind CC 2

I will be swapping out the fuel sensor and oxygen sensor this Thursday. These codes do not seem to be related to the problem as other forum members have had these issues without an impact on their engine oil temps. 2C9F has been there for 2 years.

I have been searching on these forums for a very long time no one seems to have had a similar issue.

Do you guys have any suggestions as to what can be the problem? Is it possible the overheating of the engine caused some oil lines to clog. Is this an oil pressure problem? Should I datalog a few parameters?

Also I just got an oil change at the dealer last week and am still having the same problem.

Thanks in advance,
Dynomyte

[Jeff@TopGearSolutions]

Can we assume your car is equipped with the factory oil cooler?

[Dynomyte]

Sorry I forgot the most important info. My car has factory oil cooler and additional AR oil cooler mounted in the front grill.

[j1gilles]

I'm going to go with some sort of damage due to you overheating it originally.... Maybe a head gasket or scored cylinder walls?... Next oil change look for coolant in the oil.

[Dynomyte]

I had my oil change done last week at the dealer. No coolant in oil. Also my coolant level has not changed since last year.

[Dynomyte]

Someone suggested it might be my oil thermostat that is sticking closed. I will reverse the spring later today.

[j1gilles]

Might not be a bad idea...

[135Hoser]

Yeah. I just have the factory cooler in my car. In some short spirited driving, I have issues getting the oil past 110c.

I like the suggestion of checking your oil thermostat.

[MrRager]

id look at the AR cooler first and make sure its working properly

[Dynomyte]

Just reversed the thermostat. Will go for a spin and report back. The AR oil cooler is not worrying me because even when I had only the factory cooler my temps were never this high. I will still look at it though.

[Dynomyte]

I did the bypass last night. I am really impressed at this mod. I drove for 15 minutes and could not get the car near the halfway mark (120C-250F). Weather was cool yesterday so it really did not help. I will take a longer cruise tonight as it is warmer than yesterday.

One thing is for sure, the oil coolers are doing their job.

If anyone has any more suggestions please feel free to share them.

[135Hoser]

You should get the BMS oil thermostat

http://www.burgertuning.com/low_temp...W_135_335.html

Ideally you don't want to run without a thermostat entirely, unless of course your a race car. Cold oil can be as bad as oil thats too hot.

Also you won't want to run without a thermostat when winter hits.

[Jeff@TopGearSolutions]

Originally Posted by 135Hoser

You should get the BMS oil thermostat

http://www.burgertuning.com/low_temp...W_135_335.html

Ideally you don't want to run without a thermostat entirely, unless of course your a race car. Cold oil can be as bad as oil thats too hot.

Also you won't want to run without a thermostat when winter hits.

[DallasBoosted]

Originally Posted by 135Hoser

You should get the BMS oil thermostat

http://www.burgertuning.com/low_temp...W_135_335.html

Ideally you don't want to run without a thermostat entirely, unless of course your a race car. Cold oil can be as bad as oil thats too hot.

Also you won't want to run without a thermostat when winter hits.

I have the stett stage 2 oil cooler with the 180 degree thermostat, and when cruising on the freeway in cold temps (like below 50F) the oil will just sit on 180. In stop & go and at red lights and such the temp will creep because of no airflow on the cooler. With no thermostat it definitely would never get up to temp in the winter, which would be bad.

[Dynomyte]

I can not get the BMS thermostat, I have the old thermostat version.

I am being careful when the engine oil is cold (below 210)

[SharkBait]

Unless it's always hot where you are, you should have some sort of thermostat whether you're racing or not. You want the engine as close as possible to the optimal running temperature. You don't want it to be running cold.

[Dynomyte]

So yesterday after the engine reached a good temperature (230F 110C) I did a few pulls on the highway. Temps never passed 115C/240F.

Is it possible my oil thermostat was defective? I am thinking of replacing my oil thermostat housing with the updated part# and getting a BMW thermostat.

I am suspecting a head gasket problem, I opened the coolant reservoir yesterday and saw a very small drop of oil on top of the coolant. I did my oil change last week the dealer did not mention anything suspicious in the oil though.

any thoughts?

[SharkBait]

Remove the oil drop and recheck in a week. Just because there's no coolant in the oil doesn't mean you don't have a HG issue or damage from overheating. It can be one way. If your oil temps are resolved, do some WOT runs. Check if coolant is being over-pressured and forced out of the vent.

[Dynomyte]

How can I know if the coolant is being over pressurized?

[135Hoser]

Originally Posted by Dynomyte

How can I know if the coolant is being over pressurized?

Do we have an overflow bottle? If so it'll end up in there.

And looking at the parts diagrams, I'm not seeing one aside from the expansion tank, which you shouldn't open on a hot engine I don't think.

The shop may have to connect a pressure gauge on a hose running to it, then test it that way.

There's also dyes they can use to determine if there's combustion gasses present in the coolant.

[Dynomyte]

I just took care of the Fuel Sensor and the p29f3 code. Unfortunately I now have a 2AAF code...

Car still seems to be running cool for now.