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Discussion Starter · #1 ·
Hello,

I just bought a e39 m5 from the dealer who changed the thermostat before me buying the car. The car’s oil is running way to cool and low when driving as it does not exceed 165 degrees. Has anyone experienced this?

Jay
 

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I just bought a e39 m5 from the dealer who changed the thermostat before me buying the car.
I take it then you never figured out how to get in touch with mgdmb. Just so you know 5 posts above where you asked how you could get in touch with him he had already posted his email. Reading posts is how you will become an informed owner.
I am not going to type out an answer that I have given likely a 100 times, someone else might. The answer is really easy to find with a simple search of this forum , E39 with the simple term oil temp. I would suggest you just start reading and it does not need to be a too low thread. Discussions wander here so the answers could be in a too high thread, but also read the ones where coolant and oil are low. You want to understand how these things relate for your years of ownership.
 

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I just ran across this issue. The dealer just changed the Thermostat though. Does the oil level sensor at the bottom of the pan also read temperature?
Yes that sender in the pan gives you oil temp, it also gives you a vague oil level reading. If you are getting a warning that your oil level is low and when you check it is still well above the min mark it might mean the sensor has seen better days. There are still a lot of other things that could be causing this including a broken heater block located under the hood just in front of the driver.
First you need to learn how to unlock and monitor the secret menu.
See here.
Drive it for a couple of weeks and keep an eye on Ktemp and Oeltemp and see how they behave. Even though the dealer replaced your T-stat your real issue might have been the seal that goes around that part, or many other things so the starting place for this is to monitor temps and report them. Also note what your gauge says at the same time.
 

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Discussion Starter · #4 ·
Thanks Sailor. I checked out the Oeltemp today and when fully warm it ranges between 80-94 degrees C so it’s most likely the sensor. The Ktemp is sittting at 85 degrees C flat.
 

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Don't know about that. Your Ktemp seems high unless it is really hot or maybe you were feeling racy? It is sort of looking like you might have a bad heater valve. Very hard to say at this point without more data. If the heater valve is bad in the way that keeps by passing the system and returning coolant back to the head the coolant gets hot but the oil stays cool. The valve fails many ways one way it makes both temps jumpy and often cool.
Why did yoo replace the T-stat and did you have a 69 code?
 

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I assume the dealer changed it with an OEM stat, so most of the time you should see 80. Depends on outside temp and driving though. Watch for awhile, you are not going to change the temp sender until you do an oil change so you likely have time. Keep reading lots of things can affect the temps. There will be hints in the threads that you might get a better idea. Note how fast you can get hot air out of the vents after startup. Note if you have hotter air coming out of the lower vents when they are the only ones on and the temp is set low for the cab heat.
 

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Would that throw a code?
I don't remember but we had a good thread on this last year or so ago. The guy was a pro and followed up after he switched out the whole thing, he had tried every other part prior to coming here. It is not the pump that changes things it is the valves. The process is complex and worked much better in E34/38 vintage cars than it does now but they redirect head coolant through the heater core then back to the head so that the heater core will produce heat way before the t-stat even opens.
 

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I don't remember but we had a good thread on this last year or so ago. The guy was a pro and followed up after he switched out the whole thing, he had tried every other part prior to coming here. It is not the pump that changes things it is the valves. The process is complex and worked much better in E34/38 vintage cars than it does now but they redirect head coolant through the heater core then back to the head so that the heater core will produce heat way before the t-stat even opens.
Interesting. It's probably just me over analyzing things but I feel like I've been chasing a "running a little hotter than it used to" problem. I might have to test mine, if even possible... but also not sure it's my issue. I'll expand in a new thread sometime.
 

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Interesting. It's probably just me over analyzing things but I feel like I've been chasing a "running a little hotter than it used to" problem.
Not as easy as it was on the E34/8 to diagnose. For a skilled person like yourself, might just be faster to pull the part and take a look inside. The impeller is magnetic so no noise when it gets stuck the valves also collect crud. Maintenance item on E34s so even if you find nothing likely time for a good clean anyway, cheap insurance.
 

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I feel like I'll have to take mine out to clean it just for the sake of it. Would light agitation using soft brush and distilled water suffice?
Take it out and look. If that was sufficient then it never to come out. There can be a ton of crud and the valves still work although the impeller can stop with just a minimum. I have not had much success cleaning these new version ones(left too long) and have put two in my old car.
 

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Hmmmmmmmmmm

I’ve previously gotten the six heater valve code, replaced it with a working used unit from Adam or Mike, and the code disappeared for awhile now it’s back again unfortunately but I’ve been struggling with a seemingly too cool scenario (coolant temp seems to sit at 74 in the winter when it’s cold while running on the highway). Either my thermostat is partially stuck open but maybe just in a spot where there is not a drastic change, only an issue in the winter never when it gets hot,

Unfortunately although I have a record of the previous owner getting the Tstat replaced, I’ve never touched it myself since 2017 when I got the car with 79k miles, currently at 110k. The pics I have going back seem to show similar data so maybe it’s always been like this and is ok.., argh. Seems a bit cool, gauges not at halfway on highway when car is warm in winter, but get close.

Could be impacted by aux heater valve going bad again???

Not if it always acted this way! Sorry I’m so confusing.

I have a new tstat and multiple copies of o rings but was going to do it with the water pump at some point.


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Take it out and look. If that was sufficient then it never to come out. There can be a ton of crud and the valves still work although the impeller can stop with just a minimum. I have not had much success cleaning these new version ones(left too long) and have put two in my old car.
Ok I'll take a look.
I'm switching to the newer G13++ coolant this summer and based on the DIYs, it looks pretty easy to pull it out with the airbox removed.
Thanks!
 

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I know I had to replace the heater valves twice in my E38 as it was somehow affecting the cooling system. The PO tried to rebuild the valves and it did not work. They all come with aux water pumps to help circulate the coolant while the car is off.

I dont know how it would affect the E39s but just wanted to share my experience.

As far as for E39, in my opinon, thermostat/housing seal will affect how the car will run in cooler weather.
 

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Hmmmmmmmmmm

I’ve previously gotten the six heater valve code, replaced it with a working used unit from Adam or Mike, and the code disappeared for awhile now it’s back again unfortunately but I’ve been struggling with a seemingly too cool scenario (coolant temp seems to sit at 74 in the winter when it’s cold while running on the highway). Either my thermostat is partially stuck open but maybe just in a spot where there is not a drastic change, only an issue in the winter never when it gets hot,

Unfortunately although I have a record of the previous owner getting the Tstat replaced, I’ve never touched it myself since 2017 when I got the car with 79k miles, currently at 110k. The pics I have going back seem to show similar data so maybe it’s always been like this and is ok.., argh. Seems a bit cool, gauges not at halfway on highway when car is warm in winter, but get close.

Could be impacted by aux heater valve going bad again???

Not if it always acted this way! Sorry I’m so confusing.

I have a new tstat and multiple copies of o rings but was going to do it with the water pump at some point.


Sent from my iPhone using Tapatalk
Def thermostat or housing seal failure. Do both and you should have a good long lasting cooling system without any failures.
 
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