I'm a car guy buying a car from another car guy. We've known each other 45 years. Car was a perfect silver/black coupe until a small problem (lol) with the engine that he reports as:"The first episode was a failure of the passenger side secondary (upper) timing chain tensioner - which essentially blew apart.

The plastic body of the tensioner cracked into pieces and the guide shoe appeared to have passed through the chain and sprocket.

Using the “tie wrap” method, I replace the left and right hand secondary tensioners with the new metal design.

This method ensures that the chains are held to the sprockets in the correct timing.

The can bearing caps are removed, the cam lifted, tensioners removed, replaced, and the reassembly.



During this job it was discovered the the cam associated with the failed tensioner had skipped one tooth - probably when the guide shot passed through.

By aligning the flat spots on all four cams I was able to properly align the timing of the errant cam.

Before doing this repair I also did a compression check and all seemed fine - indicating no valve to piston contact had occurred.

It is generally agreed that skipping a single tooth will not not bring the valves and pistons into interference.

This proved to be correct since after reassembly everything was fine - it ran smooth and quiet with great power.



A few months later I've had another episode wherein the the secondary timing chain in question actually broke.

It must have been weakened during the first episode.

In this case it is all but certain that valve to piston contact has occurred since that cam is now stationary with some valves held open by the stationary cam.

What needs to be done to verify valve damage is a leak-down test.

The cams on that bank will need to be removed to insure the valves all close under spring pressure and then determine if the cylinders hold pressure.

It is likely that one or more will not since the valves have been bent.



Also, the entire timing chain business should be replaced with all new chains, tensioners and guides.




I'm looking where I can truck the car and have someone reputable diagnose the minimum repair to the engine knowing full well they really want to rebuild it to make more money. I'd prefer to keep the 4.0 V8 matching numbers and seek someone that is very familiar with this minimum repair or rebuild process. Much like shops "bulletproof" a Powerstroke Diesel or "bulletproof" an AMG 6.3 liter engine I'm looking for someone that does this to the 4.0 liter. If it has to be rebuilt, bored, stroked and hotrod ed then that is okay and fun too. I'm in Fort Lauderdale and car is in Baltimore/Washington aera. I regularly have Lycoming engines rebuilt by an engine builder and I have done engine swap on a Chevrolet Suburban on the side of my house. I want a turnkey situation where I get a price quote for various repairs. Ship the car. Give incremental funds based upon levels of completion and drive away when I pay the final bill. The engine can be rebuilt anywhere in the world and prefer a parts list and to pay for the parts separately. I understand the tensioners are made of plastic and they fail. I understand that it is an interference engine and you can bend some valves.


The first thing is a person or shop that someone trusts. Any thoughts? Tom 561-346-2816

 

Welcome to the forums Tom,

Sadly this is a well known and not infrequent scenario with the early V8's. Four generations of tensioner is an indication of how long it took JLR to resolve the design flaw. Rebuilding the V8 is a costly exercise for a knowledgeable DIY'er in parts alone but a professional rebuilt will be an eye-watering sum. I wish you luck in your endeavour.

Follow this link https://www.jaguarforums.com/forum/xk8-xkr-x100-17/ to the XK8/XKR forum for help, advice and information. The 'HOW TO' thread at the top is a good place to start for information on regular issues. You can also use the US Lower Atlantic Region forum by following this link https://www.jaguarforums.com/forum/u...r-atlantic-66/ to find other members in your region.

Please read the guidance for new members ( https://www.jaguarforums.com/forum/n...ned-up-241802/ ) which answers many of the most frequent questions about getting started.

Enjoy the forums.

Graham

 

Welcome to the Forums.

Ouch.

Good luck.

 

Welcome aboard.

 

Welcome to Jaguar Forums Tom,

Good to have you with us.
Enjoy the forum.

If you haven't done so already you should add your car details to your signature to help others to help you.
If you need help with getting around and using the forum follow this link for some help Forum Help

 

Welcome to the forum - I've had my engine rebuilt from timing tensioner failure - hope you find a shop able to do as you need so you can enjoy

 

After a leakdown test we'll know if we have to remove the cylinder heads and replace the vales.



I listed my phone number. Familiar with the garage that brings you in for a small amount of work but really wants the large rebuild job. Looking for someone that has been down this rodeo and has a recommendation for a shop that can do the work. The car has to be trailered from Maryland to Florida anyway so to find a cheaper labor rate from a shop that has done this work to satisfaction for another member makes sense.

 

Hello, Tom,
I'm sorry to read about your misadventures. I wish you success resolving them.
Welcome to the forums from ElinorB.
(';')