Run an engine with no compression in one cylinder?

jaguar
xk8

#1

I’ve got a 1997 XK8 Jag. (Yes, I know. I know. I had too much money when I bought it. Now I no longer suffer from that problem.) The thermostat housing blew. Now there is no compression in one cylinder. The mechanic says its most likely a valve problem. My question is: Can I run the car 450 miles up to my brother’s mechanic?


#2

If you have a cylinder with -0- compression then when the motor is running it will be “out of balance”. How much vibration is there when the motor is idling? How much at 2,600 rpm? An inline 6 might do better than a V8. Running out of balance puts more pressure and stress on bearings for instance.

The bad cylinder maybe more damaged if parts of a bad ring or valve fall apart and metal debris scores your cylinder walls, damages valves, or the head. I’d say the trip is risky.

Anyway to find a flatbed guy to transport it?


#3

If the compression leak is out of the exhaust valve, the mixture will end up being burned in the catalytic converter. The cat will most likely overheat and/or melt. You might see if your mechanic would feel comfortable about disconnecting the injector for that cylinder.

BTW, the mechanic should have been able to pin down where the compression is going by doing a leak down test on that cylinder or just injecting air. Then, s/he would listen to where the air is going to determine definitively what the problem is. If it is going into the exhaust system, it is likely an exhaust valve; intake manifold likely an intake valve; cooling system likely a head gasket; crankcase likely the rings or piston.

Hope this helps.


#4

What if the ‘valve problem’ gets worse on the way?
Which is cheaper: a 450 mile transport, or a replacement engine?


#5

I strongly recommend against it. Who knows what kinds of problems driving that distance with a dead cylinder will cause?