V6 Overheating/pressure Build Up

[eupho]

I am gradually going through all the possible problems related to this problem. Having got the thermostat out, sadly the fault did not lie there...I would gladly have paid the price, albeit ridiculously expensive for what it is, and solved the problem. Before thinking that it may be drastic, i.e. head gasket, there are 3 remaining questions which others may know the answer to.

 

1. I had ruled out an air lock, but when I drained the system through the bottom rad hose, only about 5 litres of water came out, against the fact that the Russek manual. states that the cooling is 9 litres. It was only when I removed the thermostat housing cover, that another load of water came out. Does this suggest that an air lock was the problem?

 

2. Which of the pulleys is the water pump. Clearly I can indentify the tensioner,alternator,crankshaft....is the water pulley the bottom one next to the crankshaft pulley, or the one above. The car has got air con. To check the pump impellor I assume I just need to remove belt ?

 

3. I have put a hosepipe into both the top and bottom hoses and it runs out OK. Does ths mean that the radiator is clear, or can the water bypass the galleries.

 

Thanks. Tom

[Stevoo]

1. when thermostate is closed it will allways have water inside engine so dont worry about that, most cars bleed themselves from air locks. I normally fill rad up from both ends and fill water up through water housing and water pump. then connect hoses and fire it up. while its running i keep the header tank topped up, when thermostate opens then i keep topping header tank up until its on full. Put the cap on header tank and go for a quick drive. In morning release cap and check water level.

 

2. Dunno what engine you have but if its a cambelt driven engine the water pump is normally driven by cambelt, i think the water pup is near the front of engine by exhaust manifold end.

 

3. If you spray water in on end of rad and it comes out the other side the same colour then its not showing any signs of being blocked.

[sepulchrave]

1. No. Complete airlocks are almost impossible with this engine, what you describe is normal.

 

2. The pump impellor is not a reported issue on VR6 engines, however anything is possible.

 

3. Yes, the radiator is almost certainly clear.

 

Was the engine coolant sufficiently dilute for ice to be a possiblilty?

 

How did you determine that the thermostat was not faulty (I would have replaced it anyway having done all that dismanting)?

 

By all means replace the seal on the expansion tank cap as these are a common failure and very cheap and easy to do.

 

If you overheated the engine significantly then the cylinder head is now the most likely culprit, although I would expect some cross-contamination between oil and water.

Inspecting the spark plugs may reveal if a cylinder has been burning coolant.

[Davo]

I had a problem with my 1.9 TDi where it would overheat and pressure would build up. It was the cylinder head where the problem was, but the oil was perfect. Initially it wouldn't heat up much but the water needed replacing after a while. Pressure was getting into the cooling system from the cylinders and then when the engine was of, the pressure would force water (slowly) back into the engine. I think that is what was happening. No problems driving around town, only happened when pushing the car hard. As things got worse it would happen more severely and airlocks would occur in the cooling system and the engine temp guage whold go up while the heating would blow cold.

Got the cylinder head flettened off or something like that and replaced with a new gasket and all back to normal. Now it has started happening again after 2 or three years.

[dipsomaniac]

are both fans working ok? the temp gauge on mine always goes near the red when stationary before the fans kick in and bring the temp down.

 

these engines do appear to run very hot as there is little room for air to circulate

[snapper]

I had the overheating problem on my V6 and went completely the wrong way about sorting it.

I did the pump first and as said its not a problem on the V6 with a metal impelor however it was a bit notchy compaired to the new one.

Replaced the complete thermostat housing but the original was fine, it was a bitch of a job.

Boiled old thermostat and discovered it had failed closed, replaced it and the engine has run cooler that when i bought it.

The joggle pins in the thermostat can get stuck.

 

So replace the thermostat first

 

I also replaced the auxilary drive belt and the belt tentioner

 

dipso my car was just the same, it also ran quite hot oil temp 112 to 118 and water always to the M of normal, after all the changes, and i think the belt tentioner was part of the problem, the water temp is mostly on O or R and oil temp is a good 10 degs lower.

Edited April 30, 2008 by snapper

[dipsomaniac]

snapper - i replaced the thermostat and housing when trying to sort out the source of my coolant loss. my gauge is on the r when the car is moving. does your gauge move up when stuck in traffic?