Overheating C class - head gasket

[sally.hobson]

I wondered if anyone has had similar problems or could offer advice about my recent car problems!

I have a 1997 C class Diesel 220 with 74,000 miles on the clock.

Recently it started to overheat, preceded immediately by the heater on the fan not working. The garage diagnosed head gasket failure (cylinder 4) and replaced it. The head was pressure tested etc. and found to be OK.

I have now got the car back but if the temperature dial is to be believed it now runs hotter than it did before this happened. It used to sit happily at 85 degrees but now seems to run more like at 95. It doesn't get hotter than this. The car heater now works well and water/coolant is not being lost from the system (never was to begin with).

I took it back to the garage who used an infra red tester to demonstrate that the temperature of water coming out of the engine was no more than 75-80 and the temperature decreased nicely down the length of the radiator. He told me that he thinks the head gasket was the only problem and not something else which caused overheating and then subsequent head gasket failure.

I remain worried that there is a problem that caused the original head gasket failure, especially as I was somewhat surprised (maybe misguidedly) that this had gone wrong on my fairly low mileage merc.

Has anyone had similar problems?
Should I just not worry about the temperature gauge?
Husband determined to change viscous fan coupling - is it worth it?

Thanks for any help.

 

[Suki]

Hi Sally,
Your issue is surprising to me as I have a C class diesel with more than 170 k on the clock with out this problem! From what you have said you seem to have a disparity with what the temp sensor is telling you and what the garage is telling you. When the garage tested the water temp what did the internal gauge tell you?

I suspect that the reason that the internal heater stopped working is because you ran out of water in the radiator and nothing else.

Before your husbands replaces the viscose fan can he see if the oil from the fan has leaked?

Regards
Suki

 

[sally.hobson]

The internal guage did read about 85-90 (ie a bit higher than what the temperature actually measured) but I just find it hard to believe that the internal guage has gone wrong at exactly the same time as everything else!

I will mention to my husband to check for oil leack when he changes the fan.

 

[television]

On the Viscous fan why not do the carrot test, run the engine up to its normal 80c temperature and see if it will slice a carrot, if it does the Viscous fan is perfect

 

[Glenn Smith]

Was the thermostat replaced, it may have the wrong one in, or the old may have been letting the engine run cooler than it should have, sometimes head gaskets do fail, not as much to do with mileage but more age, type of use and maintainance (regular coolant changes help). This is what i would do, run the engine from cold, have the bonnet up and check the gauge just as the thermostat starts to open (check by feeling top hose, which will become very hot quickly as the thermostat opens) under normal circumstances the engine should not run much hotter than this, if it does whilst you are driving you have a problem, if it doesn't this is the temperature the thermostat is working at, and was probably changed during the head job. You should try to get to
the bottom of the problem as it may not cause a problem till a very hot day sitting in traffic, also whilst driving at any speed the fan has little or no effect on cooling, it's all done by air flow from the movement of the car, so will only be an issue if it runs hot whilst stationary.

 

[Glenn Smith]

On the Viscous fan why not do the carrot test, run the engine up to its normal 80c temperature and see if it will slice a carrot, if it does the Viscous fan is perfect

Run it a bit hotter and see if it can slice your finger off, then you know it's working!

 

[sally.hobson]

Definate failure of carrot test so will be replacing the viscous coupling!
We did change the thermostat before the head gasket was fixed in order to see if that was the cause of the overheating so I guess that could be a reason for it to be running at a different temperature but pretty sure it was an identical thermostat to the one we took out - might try changing it back to the original one.

Is it reasonable to be reassured by the infrared temperature probe reading 75-80 degrees after a reasonable length drive?

Thanks for all suggestions!