I wanted to know more about this noise... I just bought the car recently and it runs great. I'm just curious if I should look more into this noise or just leave it alone. I'm probably going to check the spark plugs soon.

 

It sounds like a diesel lol

 

Also, it is a 4.0 inline 6

 

Possibly a loose spark plug? It quiets down on the interstate when youre moving fast. It is loudest at idle or low rpms when driving slow. Car runs great and accelerates great.

 

OK, first things first.

That is an AJ6 engine in what is known as an XJ40, XJ6.

This should be posted in that area.

That is serious tappet noise to my ears.

First off I would change the oil, and filter. Use a good quality 20W/50 oil, nothing stupid, just good quality.

It sounds like it has not an oil change for a very long time.

Secondly, it may have had some head work done, and whoever did it was sloppy with the shims that adjust the clearances, and what you hear is that result. Very time consuming to fix, but really should be done, as that is NOT acceptable in my book.

Lift the oil cap, swirl your finger around the topside inside the camcover, and see if it comes out all black and sludgy. If it does, then "el-cheapo" oil has been used. This also needs sorting (I have ways of doing that if your interested), as the small drillings for oil supply to the camshafts may be blocked/restricted with that gunk, and oil starvation is making that noise.

 

I posted it in the xj40 forum also but no one ever answered.... How much will this cost to get fixed? I already changed the oil and the noise continues. The person before me changed the oil and had receipts to show. The car was purchased fairly cheap ($2500) (82000 miles) and the car runs great honestly other than the noise. I also tried seafoam and lucas oil stabilizer to quiet it down but not sure if it did much but the car accelerates great on the interstate and all that jazz. Let me know what I should do and how much its going to run me in labor

 

Bugga.

I have not done an AJ6 engine.

The earler XK engine takes me about a day, and I am slow and careful. Done many over the years.

The V12's, take forever, as the dumb chain tensioner is a PITA. Only done one in situ, and took 20 hours. Did mine with the heads OFF, and 6 hours for both, on the bench.

I am not sure of any Jag competent people in your area, but there should be someone. The risk of valve damage on the multi valve engines is quite high, so care is required.

It needs attention, for sure.

Shop around, see what turns up, the shims will be the major hurdle, as they are Jag specific.

Take the camcover off, and see what clearances you have, write them down in order, that way a lot of the work is pre-done sort of, and you know which ones are the culprits.

If all the clearances are within tolerances, there is something else amiss, like oil supply, etc.

 

Hi Grant,

Can you let me know your secret method please I'm looking at buying an XJS coupe with AJ6 but it's making a very similar noise.

Cheers,

Allan

 

OK.

In about 1975, my then DD S type 3.4, had sludge in the engine, not lots, but enough to concern me. Not wanting to strip the engine I looked at all the "snake oil" additives at the time, and an old timer in a service station (remember them well) said he used ATF to flush his engines just prior to draining them, HAHAHA.

Anyway, further discussions and his cars were Rolls Royce (3), Bentley (2), Studebaker, Riley etc. ALL awesome cars, and maintained to the top level.

He explained that ATF is highly detergent, and non aggressive.

His method was to add 1/2ltr of ATF per 5ltr of engine oil and let the engine run for 30 minutes at fast idle, shut it down, drain the oil as soon as you can, without burning yourself, and observe all the gunk dissolved in that old oil.

I did this to the S that same day, with his assistance, and the gunk that drained was awesome. Ran the car for a week with new oil, added ATF again, drained, still grubby, but the LH camcover was cleaner on the inside. It took a while, but it came clean, and I have used that method on all the Jags, and other cars since then. NO issues with the engine, or oil pick up, etc.

I stripped my HE for an oil leak, and the internals of the engine were as clean of any sludge build up, nothing to scrape off. This engine had done 80000kms with me, (200000kms in total) and that ATF flush had been used every oil change since I owned it.

When I did the timing chains on the AJ16, the gunk in the timing cover was scary (145000kms), and I washed it down with ATF and a stiff brush, came up clean very easily. It also gets the ATF treatment prior to a drain, and it is clean inside that camcover.

 

I have listened to that video a few more times, and I am still convinced its tappet noise.

I also know that a cracked exhaust manifold can make a very similar noise, but I am not convinced that the noise in that video is a manifold noise??????.

Just another suggestion from down here.

 

Excellent!! Thanks, I'll whip the cam cover off and have a gander. I'll check the valve clearances too just to be sure.

Cheers,

Allan

 

if I choose to do this myself what is the easiest and fastest way to fix the tappet noise once i get the valve cover off

 

The video was shot from the intake side. To help rule out exhaust issues, why not shoot a video from the other side i.e. exhaust.

And also one from the front left corner as you look towards the car to help with timing chain tensioner noises.

I'm hearing open air intake with a background of tappet, but my XJ40 did have a gentle tick tick at idle until I changed the tensioner situated just above the dizzy on the block.

 

I have to admit to mixed success in the the many 'spot the noise' competitions we get on the forum but this sounds like a combination of the click from excessive valve clearance and the gas blow from a loose or cracked manifold.

Graham