I have a 1990 xj6 4.0 (Daimler). There is no compression in one cylinder.
What is the problem(s)? Solution? Estimated cost of repair?
Thanks for your help!

 

Well it could be a lot of things but one things for sure, its time to pull that head off. Do you have water in your oil or oil in your water? Does the adjacent cylinder have the correct compression? Do you have any mechanical racket? Hopefully its a head gasket and not anything more serious although with NO compression it may be worse.

 

Thank you for getting back to me. No oil/water interchange. No racket, but the car does run rough. A compression test revealed no compression in cylinder 4. The others show good compression. Any further thoughts as to problem and probable costs would be greatly appreciated.
Again, thanks.

 

I'm wondering if it has burned a valve on number 4 cylinder.

 

Hi

My money would be on a burned out valve. This is the only serious mechanical problem that those engines suffer from generally although I think the norm is for cyl 5 or 6.

Assuming you've already done a wet test for compression then next step is to get the head off. A new valve is not expensive and the job is not too difficult if you are mechanically minded.

 

Rough running and complete loss of compression in one cyl sounds like a burned valve to me as well.

I just did the same job and finished last week. Check my thread for photos of what you may see when you pull the head off:
https://www.jaguarforums.com/forum/x...ok-like-66443/

Solution would be a new valve at the least. Exhaust valve will run about 60 USD, gasket kit about 130. I ended up spending a bit more on various things such as solvents and other nit noids. If your valve is burned but the valve seat is still in good condition and your head looks no worse than mine that should be about all you need.

If the valve seat is burned as well it will need to go to a machine shop to have a new seat pressed in. If the head is not flat or has corrosion wandering into the cylinders it will need to be welded and remachined by a shop.

I have seen rebuilt complete heads on ebay for 500 some USD, this would not be a bad route if the head is in need of much work.

The job itself is really not as bad as some might lead you to believe. You can pretty much unbolt the intake and exhaust manifolds from the head and peel them free from the head. It took me 8 hours to *remove* the intake and exhaust stuff completely and a similar time to reinstall. With the proper valve spring compression tool removing and installing valves is a breeze and you have the opportunity to install new valve stem seals.

 

[quote=gunnerman;464772]Rough running and complete loss of compression in one cyl sounds like a burned valve to me as well.

I just did the same job and finished last week. Check my thread for photos of what you may see when you pull the head off:
https://www.jaguarforums.com/forum/x...ok-like-66443/

Solution would be a new valve at the least. Exhaust valve will run about 60 USD, gasket kit about 130. I ended up spending a bit more on various things such as solvents and other nit noids. If your valve is burned but the valve seat is still in good condition and your head looks no worse than mine that should be about all you need.

If the valve seat is burned as well it will need to go to a machine shop to have a new seat pressed in. If the head is not flat or has corrosion wandering into the cylinders it will need to be welded and remachined by a shop.

I have seen rebuilt complete heads on ebay for 500 some USD, this would not be a bad route if the head is in need of much work.

The job itself is really not as bad as some might lead you to believe. You can pretty much unbolt the intake and exhaust manifolds from the head and peel them free from the head. It took me 8 hours to *remove* the intake and exhaust stuff completely and a similar time to reinstall. With the proper valve spring compression tool removing and installing valves is a breeze and you have the opportunity to install new valve stem seals.[/

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Thank you so much. Your help is greatly appreciated. Yesterday, I spoke with the head of service at a Bentley dealer I have done business with, and he thinls the same; a valve problem. Again, many thanks.

 

Thank you so much. Your help is greatly appreciated. Yesterday, I spoke with the head of service at a Bentley dealer I have done business with, and he thinks the same; a valve problem. Again, many thanks.

 

Thank you so much. Your help is greatly appreciated. Yesterday, I spoke with the head of service at a Bentley dealer I have done business with, and he thinls the same; a valve problem. Again, many thanks.