To Drive It or To Not Drive It? Can I wait to replace the engine until it actually dies?

Hi Tom & Ray ~

I bought a 1986 Jaguar Xj6 that is making some knocking, ticking, and squeeking sounds. It passed the CA smog inspection three-weeks ago…although the mechanics were afraid to rev it up to 3k. I drive it and other than the knocking it feels pretty solid.

I had Sacramento Jaguar take off the cover to see if the sound was a broken lifter/tappet. They did not find anything broken in that area, but they found a significant amount of sludge. I had them clean as much as possible, put new oil, new plugs, new thermostat, filter, etc… the other things associated with a 30k mile oil change.

The sounds did not stop. They think it is lower in the engine.

When it idles, it knocks.

When it is underload…or I accelerate, it ticks/taps rather bad.

I can coast or brake or let up on the accelerator when I’m at a cruising speed and get the vibrations into harmony where they virtually do not make any noise. However, when the engine is cold and/or whenever I have to give it gas (ie starting from a stop or accelerating) it ticks/taps loudly. The knock seems to exist or be heard after the ticking/tapping.

I am also hearing a squeeking noise lately, like brakes but I’m not applying the brakes.

So, I think the bearings might be broken. What do you think?

My real question is whether you feel it is a good idea or not that I continue to drive the car until it dies.

I realize with the amoung of sludge and engine sounds that the engine is doomed.

Is it safe for me to keep driving until it dies and then replace the engine and components or should I stop now and take immediate action to replace the engine?

I would like to get the last value out of the engine and delay my expenses if possible.

Would this do more damage to the car if I keep driving it?

Will I ultimately have to replace the same things whether I drive it until it dies or if I stop now and make the replacements?

Thank you so much for your time.

I am always in stitches after listening to your program, and I am honored and delighted to hear back from you.

Thank you,


Roseville, CA

Well you can drive it until it quits, but be forewarned that having an engine quite in the middle of a freeway is not fun and it is dangerous. At the very least drive it only with a cell phone handy, tow truck on speed dial.

Thank you for your reply.

The sound you hear could be from the timing chain, either a loose gear or chain tensioner. This I would fix asap as it can do serious damage. Since it comes from the bottom of the engine, I would look at the crankshaft timing gear as the culprit, but I wouldn’t rule out the tensioner.