First off, I'm not quite sure what the proper name is for the Variable Valve Timing Unit is, but it's almost a certainty that one of mine needs to be replaced.

What is the name of the Variable Valve Timing Unit (solenoid)?

Can it be replaced by removing the valve cover or does the timing chain cover need to be removed?

Thanks in advance.

 

I'm going to rephrase my question.

When you are told by two Jag mechanics that the VVT is the cause of the problem, what is the name of the component that needs to be replaced?

Can it be replaced by removing the valve cover or does the timing chain cover need to be removed?

Thanks.

 

The solenoid feeds oil to the VVT sprocket. I can not imagine how a dealer or anybody could tell if it is the VVT or the solenoid causing a problem without removial and inspection, but I am a rookie. The VVT and it's solenoid can be replaced without removal of the timing chain cover.

 

Sparkenzap, as for the two Jag people who think it's the VVT, I send both of them a very good description of what the symptoms are. Also, on this forum or another forum I posted a thread about the symptoms and another guy said it was the VVT or chains.

Your reply seems to be bringing up a point that's unclear to me. You mention "the VVT or the solenoid". What's unclear is, are you talking about one thing when you say the VVT or the solenoid or are there two things that could be causing the problem? In other words, are you saying the VVT, less the solenoid valve, could be broke or are you saying the solenoid valve is the problem?

 

The VVt is sprocket with the teeth connected to an outer member, and the center shaft connected to the other member. The outer piece can twist in relation to the shaft limited to a small range of motion of maybe 15 degrees, using oil to effect the move. Sort of a rotary, rather than linear, hydraulic cylinder. There is a spering return.
So, the solenoid valve takes engine oil, and pressurizes the chamber, through some ports (with seals between the outer piece and the inner).
So, my point is that if the VVT is not moving the cam's relationship to the chain, then either the solenoid or the VVT seals could be shot. Or the circuit telling the solenoid to activate.
Now, if the problem is a noise, especially a knocking sound from the front right side of the engine, you could GUESS that maybe the VVT was loosing oil and slapping back and forth. I just do not see how someone could be sure it was that and not tensioners. especially sight unseen, or for you, sound unheard.
So, my $.02 is they might very well be right, but maybe not.
Ross

 

Thanks for your reply. It is very helpful in giving me a better understanding and picture of how the VVT works and it makeup.

As for your not understanding of how a diagnosis can be made without hearing the noise, I totally agree that a diagnosis made off a written description is not a 100%. That's why I'm taking the car to the local Jag Dealer today.

I do have a couple of questions I hope you can help me with:

1) In the first paragraph of you reply you wrote, "There is a spering return." I think what you meant is, spring return. Am I right?

2) If the solenoid, VVT seals or the spring is shot, would the replacement of any of those three items require the removal of the timing chain cover?

3) Because you mentioned the noise being on the right side, does that mean that if the VVT is bad it will be the right side one that's causing the noise?

Thanks again.

 

In response to your questions, I will point out that it was late and my fingers and my brain weren't in top order. OK, the scotch didn't help either.



1) In the first paragraph of you reply you wrote, "There is a spering return." I think what you meant is, spring return. Am I right?
-Yes, of course. Fat fingers

2) If the solenoid, VVT seals or the spring is shot, would the replacement of any of those three items require the removal of the timing chain cover?
-The VVT is an assembly. It can be removed with only valve cover removal, unless there is something I did not remember seeing. I have not removed one, but I have seen it when I changed my tensioners.

3) Because you mentioned the noise being on the right side, does that mean that if the VVT is bad it will be the right side one that's causing the noise?

_ I had my head up my ***, with the mental image of just the passenger side VVT. Of course, there are two, one on each side, so the noise ciould be in the front of the engine, either side.

If you have not done the secondary tensioners, I suggest you tear into it to change them. While there, inspect the VVT for loose or leaky condition by charging it with compressed air. Keep us posted what you find.
Good Luck

 

As for the spering and the right side, I do the same kinda stuff, and I don't drink scotch, so I understand. I am glad you clarified things. It helps immensely.

I did take the car to Jaguar yesterday and will wait to see what they say. I'll let you and others know the outcome on that one.

Thanks soooooo much for your help.

Damn, I just now got a call from the Jag Dealer. Of all things it turns out it's the serpentine belt. Unbelieveable!!!!!!!!!!

Thanks so much to everyone and especially you Sparkenzap.

 

OOPS, I should have mentioned that. I paniced about three years ago on that with my wife's MY02 XJ8!

 

Actually, after the call from Jaguar and posting here I thought things out and decided the serpentine belt creating the problem doesn't make sense and I emailed Sacramento Jaguar and told them I was concerned that the belt isn't the problem. Hopefully I'm wrong and they are right. However, because of the symptoms and predictability of the knocking noise I'm expecting that I will hear the knocking noise tomorrow because I'm picking the car up today.

I'll let you know what happens.

 

Hey there Hooperdoski, I am in your area and have diagnosed and fixed my VVT's, Timing and many other aspects of this 4.0L engine. I also have a scanner and associated diagnostic software. If you need some help or second opinions let me know.

Pat

 

Thank you Pat. I may take you up on your offer.

Additionally, I also own a scanner so I'm good there.

As for the latest on the Jag, I went to pick it up yesterday. However, when I started it to check, the knocking noise was still there. The serpentine belt wasn't the problem. Now, $200 later, I'm no closer to a diagnosis than the day I brought the car in. Bummer!!!!!!!!!!!

Thanks

 

On he 17th I posted that the Jag Dealer's service guy called and said the problem was the serpentine belt. I went to pickup the car on the 19th and the noise was still there so I asked them to give the car a few more tests. Today, the 27th, I picked up the car and the invoice had written on it, "no abnormal noises."

Although I didn't hear the noise this morning when I started the car, it's not surprising that I didn't hear it because it was cold started to be driven out to the area where customers pickup their cars and the pattern has always been that if the car has been driven, bringing the engine's temperature up to normal, the noise will be there after the engine completely cools and is started again, but if it's not warmed up after that cold start then on the next cold start, say a day later, the noise won't be there.

Anyhow, bottom line .... If several Jag Mechanics can't hear the noise and my wife can't hear it then I'm going assume it's me and not the car. So, I'm going to sell the car and if the buyer hears the noise I will pay for the repairs. What upsets me about that is that I feel it's a certainty the noise is coming from one of the VVTs and I could replaced it for a lot less than what a Jag Dealer is going to charge.

To all that have helped, thank you very much.

 

Hooperdoski:
No offense, but have you been diagnosed with OCD? Seriously, if the noise is a VVT, it most likely will not cause a problem, except maybe a small cam timing error while cold. It may get worse, then you should fix it. I don't hear mine, but there might be some noise from a perfectly good vvt, considering wheat it is. You hear valves clicking under the cams don't you? You don't sell the car for that reason.
Good luck, but I would give the kitty another chance.

 

Did you drive with the Jag tech? if not then you're relying on someone else subjective opinion of your "noise" experience. If the VVT was the problem you would have either a SES "Service Engine Soon" light with a DTC for the VVT in question or you would have a rough running engine due to improper variable timing. VVT's are well understood and used on many newer engines.

Bottom line, you will have some "noises" on a running engine that may come and go. You can't get bent on finding the cause of every noise you perceive as abnormal unless it get's worse or starts throwing DTC codes.

 

Had to laugh .... OCD????? No, I don't have obsessive-compulsive disorder. And, if the valves were clicking I'd adjust them.

After 50 years of playing with cars I know the difference between noises you worry about and noises you don't. There's been one or two times the knocking was louder than normal and those times have made me cringe.

Thanks.

 

Actually, if I wasn't selling it I would wait until it gets worse, which I think it will, but I'm selling the car and don't want to burn someone. However, like I said previously, if no one else can hear it then I'm not going to worry about it.

Thanks.

 

Hi, I wonder: did you eventually sell your Jag or are you still driving it?

The noise is definitely not in your imagination: it most likely emanates from the VVT. Providing of course that the secondary tensioners have been replaced.

I'm experiencing the same issue on my XJ8 4.0 engine.

It is shocking how many garages haven't got the faintest clue what these noises might be. It's not exactly an exotic engine.

In my case it looks like an aftermath of the secondary tensioner coming apart: the 'slipper' came off and went between sprocket and chain with the sprocket leaving some heavy imprints on that piece. The chain jumped one notch, leading to very rough and uneven running, 'Restricted Performance' warning came up etc. etc.

Two garages, heavy head scratching and £200 later I decided to take matters in my own hand. Took the covers off and replaced both tensioners. The right hand side was barely hanging in there. The left hand side had come off.
Now the engine is running as smooth as before... as long as its cold.

Ones it warms up, some heavy knocking sound can be heard, slightly irregular, not fully in sync with the revs. It is definitely coming from the VVT unit on the left bank and my theory is that the failure of the tensioner somehow rocked the unit and it is now running uneven.

I will take it apart and see if it can be fixed.

Only issue is whether this can be done without removing the front cover (the big V-shaped thingy). There seem to be two opinions out, but my own impression is that that cover has to come off. Not looking forward to that. Quite a big undertaking for my (non-car-mech taste).

I will post my experience on the board once its done.

 

Another nine year old resurrection: I would guess he sold it. Haven't seen him on this forum while I have been. Easiest to buy another VVT. But . . . fix the tensioners! That is where the noise is now, unless you have bent a valve.

 

Unless you replaced the STRETCHED CHAIN, I would think that it is rattling at idle and that is likely the noise you are hearing.

Years ago, another repair shop called me with the same problem. They replaced the tensioners after the plastic 'shoe' came off and went through the exhaust sprocket. The chain did NOT break, but it was very loose.

I advised them to tear it all down again and 'at least' replace the secondary chain.
They called back a week later and thanked me. The noise was GONE.

bob