• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Pressure Problems

Share this page

B

Bearh3526

Freshman Member
Offline
I own a 1998 XJ8 Vanden Plas, 4.0 L, Just purchased the car. Here is what happen. We have had the car about a month and driven about 400 miles, the top radiator hose came off and the coolant of course was last and the car almost oveheated. The hose the put back on the clamp was never tighten, and it looks like some one had just put s water pump on it. But can not confirm that. We flushed the system, because someone had mixed the aniti freeze, with green. and replaced the thermostate and theromstate houseing. The car did fine for about 4 day no problem drove about 150 miles and the car over heated again. Also during this time I was adding about 1 qt of coolant to the car daily. Could not find a leak. Whne it overheated this time. I replased the thermostate again thinking defective, also replased the resivor cap. Now I can not drive the car because as soon as you start the car it immediatly builds pressuse. the both radiator hoses are hard as a rock, they r soft and you can squize them b 4 u start the car.So I am getting a lot of back pressure as soon as the car is started. Could this be a bad waterpump? I don't really see how. I took the cap off the thermostate housing and there is coolant up to the top of the cap so the engine is getting coolant. Just do not know if it is moving. HELP /ubbthreads/images/graemlins/lol.gif BEar. Please write me at bearh3526@yahoo.com with any suggestion. I think I have blown a head gasket even throu there is no signs of coolant in the oil. I well all comments to this problem
 
The first possibilty that comes to mind is a defective or wrong cap. If you have the old one, try it. It may also be the head gasket. Most DIY auto parts stores have a tool loaner program. Get the tol that tests for exhaust gas in the coolant. You will need to buy the solution for it. It will tell you if there is exhaust in the coolant.
 
[ QUOTE ]
Please write me at bearh3526@yahoo.com with any suggestion.

[/ QUOTE ]

First, welcome to the forum! That's a great car you have there. I agree with previous post - it sounds like you may have a head gasket problem.

I would ask that we keep the discussion here on the forum rather than email however, so that everyone can benefit from the discussion. You can set this thread as a "Favorite" (there is a toggle at the bottom of the thread) and then set your profile to receive emails whenever there is a reply to any of your favorites. That way you will know when there is a reply but the discussion stays on the forum (that's the whole purpose of the forum - to share information)

Cheers,
Basil
 
The suggestion is valid above. aAdditionally run a compression test on all the cylinders and that will disclose a leaking head gasket. If you have one you will need to remove the affected head, check it for warpage and heat set correct it. The immediate pressure build up sounds like a blown head gasket. Jack
 
Check to see whether the radiator is clogged.

Jaguar often calls for addition of two Barr's Leak with each coolant change. Over time it will clog the radiator and the water pump will build enough pressure to rupture the upper hoses or to push them off the fitting.
 
Water pump impellor failure is not uncommon, as is thermostat failure. I have had a couple of Jaguar savvy customers report that they experianced sudden coolant loss with no indication of hot temperature on the gauge, In both cases the thermostats had failed.
 
I couldn't imagine a car maker advising the use of bars leak as routine maintenance... But odder things have happened.
 
With all the plastic parts they use in the cooling system of that car I'm not surprised. Common problems are pump impellers disintegrating and the small plastic coolant lines tend to crack and get plugged by stupid technicians rather than replace the broken part. What did you find was the fix?
--
Steve D’Angelo, Service Technician
1994, XJS, v12, 6.0 coupe
1994, XJS, 4.0 coupe
Hills Motors, Jaguar, Rolls Royce & Bentley
4011 Pacific Blvd.
San Mateo CA 94403 MOBILE: 650.455.1110
 
[ QUOTE ]
I couldn't imagine a car maker advising the use of bars leak as routine maintenance... But odder things have happened.

[/ QUOTE ]i use to be a member of the British Military, i worked on the construction plant side ie earthmoving equipment and such like we always kept Barrs seal in the cooloing system as it will plug a leak as soon as it happens. dont want to say to the enemy "please stop the war as i have a leak in the cooling system and i need to repair it !!!
 
The only reason for an immediate pressure build up as you describe is a leaking head gasket. Look no further. Jack
 
Back
Top