Overheating .. I give up

[latief]

I just posted about this the other day, the car seems to like to creep-up towards the 105 degrees every now and then..at first, it works within normal range for quite a time (87) - maybe for like 20 minutes, but eventually the slight overheating happens...it seems like a random spike in temperature for some reason....

I changed the thermostat two days ago, parked the car on ramps to burp the system and let it run for a while to make sure there is no air in the system....

At first, I thought this was a an AC related issue, but i have been running without AC for the last two days to eliminate any potential issues with the system...still, temps spike for no apparent reason, and tend to stay higher after that.....

So, what could it be? New pump failing? that is really what is worrying me because i don't want to do the pump change again....

One thing I have noticed is that the small coolant pump near the battery (the shorter one) is ridiculously hot any time the ignition is on, even if the engine is not running......is that the mono-valve? and does it have any influence on the overheating issue?

New parts:

Hoses
Radiator
Pump
Thermostat (second on in 6 months)
coolant zerex g-05
radiator cap

thanks!!!!

Are you SURE that you have all the air out of the system? Is the aux fan working properly? Is there any oil in the coolant? Are there any bubbles in the coolant when engine is running?

[tjts1]

Test that your clutch fan is engaging with a rolled up news paper when the engine gets hot. You should be able to hear an audible wooosh from the fan when the rev the engine above about 90c.

[Rob Pruijt]

My 300SE (M103) did this some years ago.
Changed the fan clutch, didn't help.
Changed it again for a second new clutch, problem solved.
The first (new) clutch was not working properly, probably stored wrong.

Since I had the old type fan and pulley I bought an old type clutch first.
The second time I changed fan, pulley and clutch to the new version.

Rob

[latief]

I am suspecting an air bubble somehow, since i had the front timing color resealed 2 weeks ago ....

But i have put it on ramps and let it run for a while....what else to do?

Fan clutch was changed in august...i can hear it engaging and roaring as the temp goes up....still, even when running at highway speeds, the temp remains high so it is definitely a coolant related issue, and not an air flow related issue...

aux fans work perfectly on low-speed with AC on, and on high speed as it hits 105...new coolant temp sensor by the way.....

Head gasket changed last august..no oil in coolant, no bubbling of coolant...

my suspects are either an air-bubble, or a failing water pump...it is a Graf that was changed last august....

Thanks

Edit: Also, any impact from the ridiculously hot mono-valve?

[Stretch]

I'd be looking for some sort of blockage such as an air bubble. Have you flushed the system recently?

[latief]

What is the correct procedure to burp the system?

Coolant was flushed a number of times over the last 8 months ...once i did the head gasket, and then in December when i changed the radiator ..

I partially drained it two weeks ago as i did reseal the front timing cover...

Thanks

[JohnM.]

Squeezing the upper radiator hose with the radiator cap off is one way to burp the system. At the front of the cylinder head, there is two 13/14mm bolts right next to each other. One of these is for coolant. Fill until you have coolant pouring out, and no bubbles. This will ensure that the engine block has no air trapped inside.

Quick spikes in temperature as you describe can only be caused by large pockets of air. Seeing as all of your cooling system is new this is the only thing it could be.

[latief]

Originally Posted by JohnM.

Squeezing the upper radiator hose with the radiator cap off is one way to burp the system. At the front of the cylinder head, there is two 13/14mm bolts right next to each other. One of these is for coolant. Fill until you have coolant pouring out, and no bubbles. This will ensure that the engine block has no air trapped inside.

Quick spikes in temperature as you describe can only be caused by large pockets of air. Seeing as all of your cooling system is new this is the only thing it could be.

Does the blead-screw apply to the 104 engine also? any pictures of these?

thanks,

[JohnM.]

Originally Posted by latief

Does the blead-screw apply to the 104 engine also? any pictures of these?

thanks,

Sorry. Didn't realize you had the M104. It probably does have one. But the other alternative to getting the air out of the block is to take off the upper rad hose and pour coolant into it, until its "full". That combined with squeezing the same hose should get all the air out.

[latief]

Originally Posted by JohnM.

Sorry. Didn't realize you had the M104. It probably does have one. But the other alternative to getting the air out of the block is to take off the upper rad hose and pour coolant into it, until its "full". That combined with squeezing the same hose should get all the air out.

take it off at which side? radiator or thermostat?

thanks,

[JohnM.]

Originally Posted by latief

take it off at which side? radiator or thermostat?

thanks,

Radiator.

[latief]

will try it and update...

if this does not fix it then water pump will be the culprit i guess.....i really had a bad feeling about this pump ever since i bought it.....

Best,

[latief]

Any way to test the functionality/ Efficiency of the coolant pump?

[mpolli]

I would think it would be rare for it not too pump. Usually they just leak at the seal. Are you sure the radiator is not clogged? Are you sure your temp guage is correct? 100 or 105 might not be technically bad in traffic. Not sure. And is it really 105?