M50: Unusual temperature and heating

[Blade0058]

Hey,

I am trying to understand the problem I am having as of now and its driving me nuts these days! So let me start from the beginning. A month or two back due to the radiator cap not being properly closed the engine heated up close to red. But I manage to stop the engine prior to that and after waiting for the engine to cool down added the water which had leaked and did bleed the system for air bubbles as well. Ever since that day the temperature gauge in the instrument cluster has slightly moved towards the hotter side from the middle. Check the image!
IMAG0359.jpg

Then again during heavy traffic the temperature went up and I stopped the engine before it went passed the 3/4. Then after a week or two I decided to change the fan clutch, thermostat and water pump. I feel the problem still seem to linger from time to time. This is mostly noted after driving for a long period or heavy traffic. Also if I drove for a long period and stops the car and starts again the temperature needle goes all the way to the 3/4 and comes back. Have a look at the video attached.



So looking at all this do you think I am looking at?? whats going wrong???

[jclausen]

Get in infrared temp reader gun measure the upper and lower radiator hoses when the engine is warmed up

[tonynang]

Is it still drinking water? Cooked thermostat ? Blown head gasket?
Tony.

[moroza]

Behaves like my M30 after I changed the coolant and didn't bleed fully. I think you've still got air in the system.

[Blade0058]

Sorry for being dumb! What should I be looking for in that exactly?

Get in infrared temp reader gun measure the upper and lower radiator hoses when the engine is warmed up

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The water level doesn't drop. It seems to hold for good week or more. Then it drops around 50ml. Which is very little I thought... At least my mechanic is suspecting its a head gasket? Has this happened to you? If so how did you diagnose the head gasket?

Is it still drinking water? Cooked thermostat ? Blown head gasket?
Tony.

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Another member from the forum also suggested a very detailed process for bleeding. I am going to do probably on Tuesday or so! Will update afterwards. Till then please enlighten me with your wisdom

Behaves like my M30 after I changed the coolant and didn't bleed fully. I think you've still got air in the system.

[Ricky318i]

Please let us know what was the outcome of re-bleeding the motor.

[Blade0058]

I sure will! Still didn't do it... Got stuck with some other work!!

Please let us know what was the outcome of re-bleeding the motor.

[JoeGons]

I have had similar problems.
I found that I had to let a lot of coolant bleed off and topping off before things returned to normal.
After the extended bleeding process, everything is fine even in the worst conditions.

[Blade0058]

Thanks Joe. I am also doing the same as of now! In a few days let me update the thread how it goes. Thank you for all the responses!

I have had similar problems.
I found that I had to let a lot of coolant bleed off and topping off before things returned to normal.
After the extended bleeding process, everything is fine even in the worst conditions.

[Blade0058]

Folks,

Very sorry for the delay. I have had bad timing one after the other... So let me share the latest. After bleeding the cooling system I have been using the car. The tempreture gauge needle still seem to be little beyond the half way mark. Best thing was on last Tuesday a heater water hose burst. I was fortunate enough that it happened at the car park. Not on the road. So had to replace that hose. Now I am considering replacing all the hoses since I am sure its been a while since they were replaced.

So... as of now I am clueless!! I hope things will settle down

[JoeGons]

Might seem like a bit of a strange question but did you turn on your heater while bleeding?
The heater is a big hoarder of trapped air.
Joe

[Blade0058]

Yes I did. I bled the system few times before that incident.

Might seem like a bit of a strange question but did you turn on your heater while bleeding?
The heater is a big hoarder of trapped air.
Joe

[JoeGons]

Kool!!

[Blade0058]

Still I am not too sure whether things have been fixed! I will update the thread as soon as I see an improvement of the situation.

Kool!!

[Blade0058]

If anyone is still following this thread this is the latest!

Recently changed fan clutch was swapped from a Behr to Sachs. There is a difference in the speed in which they seem to operate. So now I have changed the Thermostat, fan clutch, water pump and one heater hose. But still the temperature gauge remains little over halfway mark. I have done the bleeding again and again according to specific set of instructions I received from a member which actually kind of tally's with the method recommended in the service manual of BMW.

Any ways... This seems to be leading towards head gaskets!! If anyone have any suggestions or advice they are most welcome at this point in time!!

[m735is]

Have you measured the actual temps at different points of the radiator and head to see if it really is hotter?

I'll have to do this to my 92- my temp gauge reads just above the half way mark also- but I have something electrical going on with the cluster.

Once it gets up to temp, the gauge stays right there, so I haven't really worried about.

[Blade0058]

No I have not done it. Let me try and do it soon! What exactly should I expect out of the temperature measurements?

Have you measured the actual temps at different points of the radiator and head to see if it really is hotter?

I'll have to do this to my 92- my temp gauge reads just above the half way mark also- but I have something electrical going on with the cluster.

Once it gets up to temp, the gauge stays right there, so I haven't really worried about.

[JoeGons]

My gauge is usually a needle width above the mid position.
As long as it does not go above that, I'm happy.
All that's left to change is the temperature sensor.
There are two on the left side of the head.
sort of next to each other.

One for the coolant and one for the engine temp to the ECU.
Very hard to see but the one you want is the one towards the rear of the head.
#13

E34 Vanos Clyn Head.jpg

12621710511
ENGINE COOLANT TEMP SENSOR
From:
07/01/1986
To:
Supersedes:
12621710512
(09/01/1985 — 06/13/2013)

[Apollo65]

If anyone is still following this thread this is the latest!

Recently changed fan clutch was swapped from a Behr to Sachs. There is a difference in the speed in which they seem to operate. So now I have changed the Thermostat, fan clutch, water pump and one heater hose. But still the temperature gauge remains little over halfway mark.

Please post a head-on picture of the gauge with the hot reading.

And have you changed the temperature sender ? It is screwed into the cylinder head under the manifold, brown tipped, probably 25 years old, and could be the problem here.

Someone suggested taking temperature readings at various spots on the radiator and engine. Use a laser temp gun for this. It costs $10 shipped worldwide, off ebay. For this purpose, you don't need anything more sophisticated than that.

But lets have a look at the gauge reading first..

[Apollo65]

Wait a sec. You've posted a video of your gauge in your first post. Ok.

The needle is behaving abnormally. Wobbles too much. Can be seen on the close up in the first half of the video. It is not supposed to wobble, or move back and forth. Either the gauge, or the brown tipped temp sender, is damaged.

Shoot us another video to confirm. This is what you need to do. Start the engine and let it run until the temp is at the problem level. Go for a drive. Then shut the engine down and start shooting close up video of the gauge. Then flip the key to full on position (the next position is cranking). The gauge will activate. Stay on it for 1 minute. Then flip the key to the off position. The gauge will deactivate. Then start the engine and keep the camera on the gauge for another minute. Time this and keep it close up head on like in the first half of your earlier video. That should be all we need to see.

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Also if I drove for a long period and stops the car and starts again the temperature needle goes all the way to the 3/4 and comes back.

This is not unusual. Heat soak. It will come back to normal within a minute of the engine running. Not anything to be concerned about.

[Blade0058]

Thank you @JoeGons and Appollo65.

@Appollo65: Let me do what you suggested and update the thread. I also really hope its something minor but not major.

On a separate note, what do you all think of Silicone water hoses instead of the rubber hoses. I have replaced my the blown up heater hose with a genuine. My idea was to change whatever that's required with OEM or Genuine. A friend suggested to use aftermarket silicone set. Just wanted to know if anyone have used those instead of the rubber during these sort of failures!! Like to hear yhour thoughts.

Wait a sec. You've posted a video of your gauge in your first post. Ok.

The needle is behaving abnormally. Wobbles too much. Can be seen on the close up in the first half of the video. It is not supposed to wobble, or move back and forth. Either the gauge, or the brown tipped temp sender, is damaged.

Shoot us another video to confirm. This is what you need to do. Start the engine and let it run until the temp is at the problem level. Go for a drive. Then shut the engine down and start shooting close up video of the gauge. Then flip the key to full on position (the next position is cranking). The gauge will activate. Stay on it for 1 minute. Then flip the key to the off position. The gauge will deactivate. Then start the engine and keep the camera on the gauge for another minute. Time this and keep it close up head on like in the first half of your earlier video. That should be all we need to see.

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This is not unusual. Heat soak. It will come back to normal within a minute of the engine running. Not anything to be concerned about.

[ross1]

This looks to me like either air in your system or poor circulation. Nothing wrong with that gauge or sender, save your $.
A loose cap won't cause overheating, unless of course you've lost coolant.
The original, and some replacement water pumps, have plastic impellers that loosen on the shaft. In the early stages of this failure mode you may see intermittent overheating.
My advice is be CERTAIN the system is properly bled and proceed from there.

[Blade0058]

So you are saying to bleed the full system and try it! Yes, that's something which I didn't do or for that matter my garage guys didn't do. Will try it out!

[JoeGons]

So you are saying to bleed the full system and try it! Yes, that's something which I didn't do or for that matter my garage guys didn't do. Will try it out!

What exactly have you been doing?
What do you mean "...bleed the full system..."
To bleed the system you must have the engine running, turn on the heater and with the radiator cap on, open the bleed valve and let the coolant run out for a while. Then top-up and do it again. The bleed valve is the little round disk next to the filler cap.
Bleed screw E34.jpg

This is a good write-up.

http://blog.bavauto.com/12247/bmw-an...ostics-how-to/

Towards the end of the write-up there are detailed instructions on bleeding.

[Blade0058]

My sincere apologies to all for the miscommunication. Yes I have bled the system few times earlier but since the problem persist I thought of draining the full system and refilling. This is what I meant to say! Thank you for those who pointed it out.

I have done the full system drain but still no difference.