I just joined this forum about 2 weeks ago and did not think I’d be seeking help this soon. I recently bought a 1999 Jaguar Vanden Plas and it seemed to be in good running condition. Well now I have an overheating problem. It overheats after driving just under an hour and turning on the interior heating seems to slow/bring it down somewhat. Sometimes I need to pull over, turn off the engine, let it cool off, then I’m able to drive again for about another hour.

Key points I have noticed: 1) Seems to be using coolant every three days, 2) have not notice any specific leaks other than once did I notice some coolant dripping from recovery tank below near left fender wheel well.

Reviewing previous owner’s service work orders it seems the following was recently done in August 2020 due to overheating; 1) replace Expansion Tank, 2) replace coolant crossover (plastic) pipe in front of thermostat housing, 3) chemical flush and refill cooling system, 4) pressure test cooling system. Other cooling system previously done was 2007 chemical flush and refill cooling system, 2005 replace T-Stat Housing Unit (plastic), replace both feed & return heater hoses, and 2004 engine and coolant flush. What stands out is the water pump has never been replaced. Hoping forum suggestions can resolve my overheating problems. Thanks all

 

The coolant being pushed out of the recovery (overflow) tank could be due to:

1. Overheating (high pressure in the cooling system, almost boiling)
2. Small combustion leaks pass the head gasket(s) causing pressure build-up in the cooling system

I would first check the following:

1. Are the radiator fans operating correctly, i.e. do they go to high speed when the engine temp is high?
2. Check/replace the thermostat and the water pump.
3. Check for presence of combustion gasses in the coolant (combustion leak tester) - this would confirm (or eliminate) head gasket leaks

 

Thanks MS for your suggestions. The fans do run properly so based on service history I will replace the most obvious which is Thermostat Housing Unit (metallic), water pump (metallic impeller) and hoses. I truly hope it doesn't turn out to be the head gaskets! Will post outcome after completion of project.

 

You mentioned seeing some coolant dripping from the recovery tank. That shouldn't happen. The pressure cap allows fluid to flow there when the engine temp. rises, but it should be drawn back as the engine cools, unless the pressure cap is defective. Several members have reported defective caps after only a few months, so it might be a good idea to get another one.

 

Maybe the expansion tank lines are crossed. I know there’s an image of how they should be on here somewhere.

 

Since the expansion tank was one of the most recent replacements I checked all 3 expansion lines and they are correctly placed. However, I will include the recovery tank cap and recovery line connection from the expansion tank as part of my cooling system repair project.

 

Thanks RJ & Addicted. Truly appreciate your newly added input.

 

Replace the thermostat housing with the aluminium version and install an OEM thermostat. Bleed the cooling system per the Workshop Manual instructions to remove all trapped air.

Does the heater work correctly?

 

Thanks NBCat. I will definitely include bleeding the cooling system to the project. Yes, the heater works correctly - I have turned on the heater to help cool the engine.

 

Here is the picture of the cooling lines: Be sure!

 

Thanks for the picture Jim. I'm downloading it for future reference. Yes , all cooling lines are correct.