Replaced Thermostat - Still overheating
#21
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I drove the car for 15 miles on the highway - no problems, temperature normal.
Sitting at the light on the off ramp the temperature gauge started ticking up, went up to 3/4 and then leveled back off. Coolant light came on and went off.
I drove home 3 miles with no problems. No coolant spilling, fan wasn’t running.
Coolant droplets and residue were on the top of the overflow compartment. After it cooled I opened the cap and added ½ gallon of antifreeze to bring it back to MAX.
I started the engine, unscrewed the bleed screw and let the car run for 3 minutes as it bubbled and began overflowing through the screw.
It’s getting dark here so I’m done for the night. Tomorrow is another day, I’m open to suggestions/insights/encouragement!
The oil is fine.
#22
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When the Jaguar V8s came out, there was a spate of water pump problems with impeller blades breaking off, so coolant didn't get pumped around. However this problem was fixed during the production of the 4 litre engine. The later 4.2 litre engines obviously have the later pump, but clearly if everything seems OK with coolant level and thermostat, one has to carry on looking.
So if the bleeding doesn't work, maybe look at the pump, which is unfortunately a bit of a PITA to remove. Only other thing would be a clagged up radiator, either externally or internally. Maybe check the air flow side of the radiator first to make sure it is clear, then the pump.
Edit
Has it got the correct coolant in ? If somebody put in the old type, (non-OAT type), then there is a possibility of sludge forming, because the two don't mix, and that will clog up the system
So if the bleeding doesn't work, maybe look at the pump, which is unfortunately a bit of a PITA to remove. Only other thing would be a clagged up radiator, either externally or internally. Maybe check the air flow side of the radiator first to make sure it is clear, then the pump.
Edit
Has it got the correct coolant in ? If somebody put in the old type, (non-OAT type), then there is a possibility of sludge forming, because the two don't mix, and that will clog up the system
#23
#24
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Combustion chamber gas pressurises the coolant and the coolant then gets blown out of the header tank past the pressure cap. One feature of HGF like this can be pressure in the coolant jacket even when the car is completely cold.
There is an awful lot of coolant disappearing here, and there should be some evidence of where it's going, I'm sure.
#25
#26
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I have no idea when coolant goes into combustion chamber causing "smoke" and particularly in n/a engines.. maybe its just matter of high mileage and real age of gaskets or total damage of gasket in turbo example described above.
I heard of problematic 4.2 NA motor in comparison to SC version, but without any proof yet.
#27
#28
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Some questions.
When you say you replaced the thermostat housing, was this the complete thermostat unit housing?
Can you get the coolant system pressure tested?
This may not show anything, as I suspect the leak is very small.
Does/ has your low level expansion tank alarm worked?
Can you check the coolant for combustion gases?
At least this will put your mind at easy that it is not the cylinder head gasket leaking.
You may I suspect, have a small leak,(very small) on the coolant pipe between the back of the water pump and the throttle body (this would be the prime suspect.)
As it would not be visible in most part as the majority of it is under the air manifold. Similar to the valley pipe position on the S type R's. and a lot of the coolant would evaporate off.
Mine started to have low coolant level/alarm and I could not figure it out, nor find the leak. But eventually did when the thermostat housing went.
Throttle Body coolant line AJ 811763, was the pipe. Mostly hidden under the air manifold. There is a larger dia pipe about 4/3" into the back of the water pump, and a 3/8" into the throttle body. The connection reducer (plastic fiber type) between the two pipe sections had cracked, and was leaking coolant out between the cylinder heads, and down the back of the engine. None was to be seen on the ground, only a small puddle on the under tray, and soaking the foam.
What makes me suspect this, option of leak and low coolant, is the turning on of the climate control, and the overheating, as the water is further reduced from the cooling system and is pumped into the cabin heater. Together with the then normal running temp and then the overheating over time as the coolant is lost.
It took weeks for mine to register low level in the expansion tank.
Then again this explanation only really works if the expansion tank level alarm is not working, and this could be rubbish and not this pipe or coolant leak at all.
But a good story and a better ending than cylinder head gasket replacement.
below photo of the hose I am talking about. #7
https://www.jaguarforums.com/forum/a...ody-hose-2.png
When you say you replaced the thermostat housing, was this the complete thermostat unit housing?
Can you get the coolant system pressure tested?
This may not show anything, as I suspect the leak is very small.
Does/ has your low level expansion tank alarm worked?
Can you check the coolant for combustion gases?
At least this will put your mind at easy that it is not the cylinder head gasket leaking.
You may I suspect, have a small leak,(very small) on the coolant pipe between the back of the water pump and the throttle body (this would be the prime suspect.)
As it would not be visible in most part as the majority of it is under the air manifold. Similar to the valley pipe position on the S type R's. and a lot of the coolant would evaporate off.
Mine started to have low coolant level/alarm and I could not figure it out, nor find the leak. But eventually did when the thermostat housing went.
Throttle Body coolant line AJ 811763, was the pipe. Mostly hidden under the air manifold. There is a larger dia pipe about 4/3" into the back of the water pump, and a 3/8" into the throttle body. The connection reducer (plastic fiber type) between the two pipe sections had cracked, and was leaking coolant out between the cylinder heads, and down the back of the engine. None was to be seen on the ground, only a small puddle on the under tray, and soaking the foam.
What makes me suspect this, option of leak and low coolant, is the turning on of the climate control, and the overheating, as the water is further reduced from the cooling system and is pumped into the cabin heater. Together with the then normal running temp and then the overheating over time as the coolant is lost.
It took weeks for mine to register low level in the expansion tank.
Then again this explanation only really works if the expansion tank level alarm is not working, and this could be rubbish and not this pipe or coolant leak at all.
But a good story and a better ending than cylinder head gasket replacement.
below photo of the hose I am talking about. #7
https://www.jaguarforums.com/forum/a...ody-hose-2.png
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