One day a week or so ago the XJ6 developed a unusual noise. I thought maybe I had a tappet guide loose. My 82 did not have the shakedown kit installed. I parked it. I ordered the kit. I waited. Saturday I open up the exhaust side valve cover and everything looks fine. I installed the kit anyway. Sooner or later.

I fire it up and it runs so quietly I thought maybe I'd fixed something. Took a run around the block and stopped at the corner store. When I started it back up the sound was back. Limped home at idle. Opened up the intake side valve cover to check, and everything looks good in there too. no stake downs installed but also no evidence of any molestation of the guides.

I'm hoping someone her might know what I should investigate by listening to it. Here's a link the a short video where you can hear it.

 

Have you tried the long screwdriver trick. Use it as a stethoscope. Put the tip to the engine and the handle to your ear and you will locate where the tapping is coming from. Could be a weak tappet or valve spring.

Roger

 

Listened 6 times.

If its quiet when cold and tappy when hotter then tappets are out of adjustment.

I have heard way worse, and a time consuming reshim of the tappets fixed all the noise.

The tension of the top timing chain may be a tad slack, hardto isolate on that video.

Still sounds like simply noisy tappets.

 

The tappet shims are meant to rotate and if they have become slightly deformed then this noise (which can be shockingly loud) will come and go. I had this on two xj6 cars. Entirely harmless. You need do nothing about it.

 

About three years ago I had a similar noise. Couldn't be sure where it was coming from, but to rule out valve guides I put in a stakedown kit (which I had been meaning to do anyway). When the noise strongly and rudely persisted, I threw up my hands and had it diagnosed by a shop. Turned out to be a failing water pump.

Replacing a water pump is straightforward and not difficult, although removing the fan vis-a-vis the shroud was a bit annoying.

Good luck getting to the bottom of this. Noises can be a pain.

Andrew.

 

OMG. Why did I not turn to the forum first?

I'll open her up and measure all the gaps and order shims to see if I can quiet it down. Not very Jaguarish this way!

Thanks for all the replies. I have a automotive stethoscope and I definitely think it's in the head not the water pump.

I guess my only real concern is that I thought dohc engines lost valve gap over time unless something causes a valve to not seat properly.

Compression is 150, 148, 152, 138, 149, 151. 1-6. So maybe cylinder 4 has some build up or wear that's keeping it from seating completely? I could have sworn I heard a different sound when running it up to pressure when testing. A hiss.

 

Loose spark plug, or crap under the spark plug seat, common on that engine.

Makes a strange hiss and "popping" sound.

Put a SMALL, and I mean SMALL amount of water around the plug well, start it up, look for bubbles.

Replacing the tappet shims is a huge time consuming task.

You need to measure the gaps, write them down in order.

Remove the camshafts, retrieve the installed shims, ONE at a time, measure their thicknes, then calculate from what you wrote down what new thickness shim is
needed.

Re install the camshafts, camcovers, etc, and start it up, and see hw good you are.

 

Aughhhh!

This issue reduced down to almost inaudible. Last few days Alfred has been running so well! I planned to measure gaps this weekend and order some new shims to make everything perfect.

Then I tried to start Alfred at lunch for a quick trip. Ran great this morning on my trip to the office. Fired right up and sounded awful! Knocking. Loud knocking. I shut it right down. Started breathing deep and trying not to panic.

I had to get a uber and go. I'll try to determine what's up as soon as I get back. Oil was fine and no leaks under him. I'm a bit freaked out imaging things gone wrong. I have no idea how to proceed other than towing him home. Any next step suggestions?

 

If the noise is coming from the "exhaust" side,..I would be looking at the tappet "buckets " that are press fitted into the head. My old Jag engine had the same sound even though I had a stake down kit in it. A bucket had come loose and when cold,..it stayed put. Once it warmed up (exhaust side) it made that sound . if you have a stake down kit,..check to make sure it is tight and really staked down. One of the tappet guides (buckets) kept coming loose in its bore and the stake down kit screws would back out - making that same noise...my 2 cents.. the stake down apparatus was supposed to "stake it down" but it did not over a period of time

 

I have a complete running engine and transmission that you can get for $0.00.
If the cost of parts and labor is too much, it might be feasible for you to calculate the cost of picking up this engine It's plug and play and it's FREE.
8 hour drive each way.

 

What an incredible offer! Oh do I hope it doesn't come to that! But thank you very much either way!

I'm going to tow and try to bear running a compression test. Should be informative. It pains me to hear such sounds coming from such a beautiful machine! While I'm turning it over I'll record some video for diagnosis.

Thanks again Sanchez!

 

I'll pull the covers and check my stake down kit before I call for the tow! I'd love this to be a loose tappet guide! Hell anything in the head is better than down below!

 

Alfred turned over and did not fire up. Completely out of character as it always starts before I can get off the ignition. So strong. Not today. I readied my phone to record his efforts. I tried him once more. He turned, and he stopped. Stopped, mid spin. I sat back, gutted.

It's seized. Turns a few degrees and rebounds.

I'm going to have him towed home and start to plan his recovery. David Boger is nearby, and that is significant. And Sanchez has already given me hope! I am really pleased that I've taken Alfred out the last few summer nights and driven him at high speed on the highways and cruised the country roads. He felt really smooth, strong and solid. Just an awesome feeling and a great car.

This is not the end of this car's story.

 

Whew??? Been there!!! But, Sanchez and David Boger
offer great alternatives.


Carl

 

@JigJag: Sent you a PM. Not sure how the PM replies work or whether you received it. Let me know here

 

Epiphany???


Cranks and rebounds ?? New description to me. But, well known as
starter "kick back".


Two reasons:


1. Starter failing. Been there, way back when . 65 Corvair Monza. Began when wifey took driving test. Fixed car with remanufactured
starter. Wifey ?, took her out to a nice dinner.


2. Ignition timing slipped to "too much advance".


The good? It is trying to fire up.


Carl

 

Oh, wifey passed driving license test with flying colors!!!


The good life restored.


Sure miss her, so much in so many ways. A really good gal.


Carl

 

Have you pulled the plugs and tried turning it over? Could by hydraulic lock, coolant wont compress!!! Worth a shot!

 

A bent inlet valve will widen the tappet gap hugely and make a terrible noise. I had this shortly after a rebuild. Series 3 engines have the wider inlet valves so a lazy valve return can cause it to 'kiss' the piston as it comes up. However once bent the noise will be continuous and will not quieten.