I'm "rebuilding" a late '2000 XJR, and now I'm facing with a problem. The engine has ticking noise, and rough idle, so I took of the head covers. The last intake valve (cyl 8th, or left bank 4th) has too high, 0,55 mm clearance. All of the other valves, even the other intake valve of this cylinder has the right clearance. That's would not be strange problem, if the cam of this valve is weared. But the cam is like a new one. Strange that this valve's tappet (under the cam) is sitting lower in the cylinder head, than the others. I made a compression test, and this cyl has zero comp. I filled up this cylinder with carbon cleaner across the spark plug hole, when the intake valve are opened, trying to remove any carbon, if that causes the problem, and the liquid level in the spark plug hole goes down very-very slowly, that means, the compression losing is not caused by the piston's ring or cylinder wear.
I checked the position of the timing, and that is OK. I already have iron chain tensioners. Do you think that there is any other possibility that the valve bended? I'm hoping.

You should have to know, that this car was sitting almost two years, before I bought it. But it was started almost every 2 months under this period.

 

I forgot to mention, that I still can't use the car on the roads, only tried it in front of the garage. It was idling for an hour with some rev til 3000rpm, but the ticking did not go away.

 

The following comment is far above my experience level but there have been reports of valve stem guides moving during overheating.

 

If you have a valve clearance problem, the ticking will not go. It needs fixing.

Why was the car sat for 2 years?

There is a problem with these engines if overheated, the valve seat can drop out.

I would suggest getting the correct shim and fitting it to the offending valve. If this does not cure the loss of compression (and ticking) then you will have to remove the cylinder head, and check the valve/seat.

 

That could be the reason, it sounds logical. Thank you. But can the valve stem guide -if that is moved down towards the cylinder - stop the valve, before it closes the intake port? I don't know really the construction of this engine's that part.

 

-Yes I know that a clearance usually won't go, I just thought that because of the car was sitting so long, there are corrosion between the valve lifter and it's bore, or there is any debris around the valve's area. I just waited a wonder by the new synthetic oil, and the first fully warming after that long sitting.

- I have a thread - Two XJR's in one - where I told that this car was damaged at the front. Maybe the engine was not stopped after the accident, and it was working without water. Sadly I don't know the story. Anyway, all of the parts are clean like new inside the cylinder head, the engine oil was very clear, I don't see any colorisation. ..and why just one valve (or that's area) is hurted, and why the cooler and bigger intake valve? I don't know it is related or not, but the water level sensor is not working. I always got low level warning.
- The valve seat, or the valve stem can move out from its original position? I don't know the contruction of this part of the engine. Did you mean valve seat?
- Yes, the less I have to do is taking out the camshaft, and maybe I will see why the valve lifter does not come back to the level of the other lifters, in the cyl. head? I'm courius, if I have a micro camera, could I look at the inside of the cylinder by the plug spark hole?

 

Steve, what's the engine like in the other car? Also, the mileage and manufacture year of both? I ask as they might be interchangeable parts, like swapping a head?

If you can make one good engine out of the two?

The valve guides are pressed in, if the engine overheats, the head expands and the seat can fall, this would cause the valve not to return to it's original closed position once the engine cooled, the seat and valve are trapped.
But like you, I'd have thought more than one valve would suffer, and maybe show signs of coolant in the engine oil, so I understand the way you are thinking, it is strange.
Anyway...
The water level sensor is an easy fix, in the header tank there is a float, these often stick in the low position, I've cured a few just by putting my finger in the tank and sliding the float up and down a few times to free it off, you might need to suck/drain out a little bit of coolant to see the float.

If you confirm the valve isn't returning to it's seat (get your camera in the cylinder with valves closed) the guide could have dropped holding the valve open slightly (answering your loss of compression)
I've just taken a picture of an XJR head with the valves removed, you can see the little guide and how it can drop out. I hope this helps you understand.

Lastly another suggestion, a broken valve spring. To fix this you'll need to hold the valve up with compressed air and a spark plug adaptor.
Either way, it's no biggy.

 

The old way to do this if no adapter and compressed air is available, is to feed a piece of thin rope into the cylinder through the sparkplug hole when the piston is at BDC before the compression stroke, then rotate engine to use the piston to compress the rope against the valve heads to hold the valves up.

Oh, and don't feed the whole piece of rope in, you need to be able to pull it back out again afterwards.

 

Since the gap is too large, and there is moo compression, there is little possibility that a new shom will fix it- and I do not think there are 55 mm thicker shims than "standard"/ Ot seems like there must be something holding the valve open- so a look see with the scope seems in order.
I also doubt the compressed air method will hold this onwe shut, unless you have lots of air- with zero compression, there is a pretty good leak.

 

Good point

Anyhow, if the valve has excess clearance, and the valve is still not fully closing, then it's heads off time for a new valve seat anyways.

 

Thank you all of you guys for the useful answers! I don't have such a videoscope to look inside the cylinder, but I will try borrowing one from a service shop. Anyway it seems to me, I can't avoid removing the timing and the camshaft. Even if the scope would not shows any iron piece droved in the metal of the head's valve's seat, I have to remove the camshaft, because I won't find the cause of the problem without it. But without removing the head I can only fix a broken spring, or a jammed lifter problem. If the valve's stem moved, or the valve is bented, I have to remove the head. I'm hoping for the broken spring.

The other car is a 1998 XJR, with 350000 km, but I'm still did not checked the engine number. Shame on me. Maybe the engine was changed under warranty, like on the newer car. Anyway the 1998 car's engine is idling like a swiss watch (it does not means ticking :-))). I can't get over it that when I got the 2000' car, the engine oil's color was like new, I haven't seen ever such a clear used oil, except right after oil change. Maybe the oil was changed just before the accident. ???
Actually the car is almost ready for painting, but here are this problem.
So one of the next weekend I will remove the cam, and share what I found.

Thanks Sean for the water sensor idea, I will do that!

 

That was the cause of the low coolant level warning! Now it's gone. Thanks again Sean!

Back to valve clearance problem: I did not have time to check the valve lifter this weekend, maybe next weekend.

 

I'm back again. The mystery still is not solved. I removed the cam, the valve's springs and seals. I even removed the next intake valve spring too, to measure the differences between the two valves.

The distances between the top of the valve's stems and the bottom of the head are the same, so the stem did not move lower towards the cylinder. The two valve springs are the same. The valve's seal is not burned. I turned the crankshaft a little to give enough space for trying to move the "wrong" valve up and down. It moves freely, but if I pull it up, at the last 1-2 mm the valve begin to jam. It can get fixed (!!!) by itself at the top position. Maybe it means that the valve bent. But there's again.. how, and why? If something got between the valve and the head (valve's nest), even in this case I hardly believes the piston can touch the valve, or that had to be a very big debris.

So I think I have to get a 90 degree videoscope if I want to avoid the "head off".
???

 

I think the pictures tell you everything. The valve's seat moved out.
The valve bent, the piston has no any damage. Do you think, this kind of problem is repairable, or I need an other cyl.head?

 

Steve, as you have a spare car/engine, I'd suggest using another cylinder head. The original head can be fixed, but I don't know at what cost, and the other issue is warping, it may need skimming, and a number of valves/seats/guides replacing, not just one. It can get very expensive, quickly!!

To use the spare car's cylinder head we need to know if it's AJ26 (Model year?) and the model year of the project car's engine (AJ27?) Because there is one difference in the two cylinder heads, i.e. the cam position sensors. The 26 has one, the 27 has two, so, you might need to swap an intake camshaft.....

 

The older car's first license plate getting date is 15.10.1998, chassis number: SAJJPALF4CR8538xx, and the car of this topic was produced at 08.2000., SAJAA15N91MF230xx, but it has a replaced steel cyl linered engine.

No problem if I have to replace all of the parts (except the valves, and guides, and tappets) from the faulty head to the other if it is possible. I only worry about the valve's oil seals, because the older engine has much higher mileage, and it's easier to change on the table, then later in the car in case of oil burning.

 

I would like to avoid taking apart the other engine til it is not necessary.

So I would like to buy an other used head. I found one but I need yours help! Will a 1999-2000 4,0 VVT (steel liners) head to match my 2000.08 but replaced steel linered Supercharged engine? No matter if the intake cam is not interchangeable.

 

I just wanna let you know, that I replaced the my SC cyl head with a used N/A cyl head. I used the SC cams and valve tappets. It works well, but I got low oil pressure warning at hot. I measured, and there is 0,6-0,7 bar at hot idle.
I was thinking (hard :-)) and the possible reason gets my mind. What a shame, I forgot, that there is a oil feed hole on the VVT (N/A) cyl head, for the VVT mechanism, that is plugged on the S/C head. That has to be the reason for losing oil pressure.

Now I have to take off the front cover again to plug in that oil feeding hole!

 

Here is an old TSB for the OPPOSITE problem. The new heads are supplied with the hole plugged.

You need to install a plug.

I would tap and thread a bolt with sealant or a tapered plug.

bob gauff

 

If I had this information before the cylinder head replacement!
Anyway, thank you very much! I was thinking how to make that hole plugged securely, so thank you for your advice. I will choose the "tap and thread a bolt" method using bolt fixer "glue".