Hello all:

I'm new here so please don't shoot me. Ok here is my problem. Just bought a 2004 XJ8 VDP 4.2 liter with 38500 miles on the clock 2 weeks ago from a private owner. When I inspected the car (twice) before purchasing the car, it ran perfectly quite and strong. Now at first start up after sitting overnight or for 5 plus hrs I get a rattle that sounds like valve train noise that lasts 1-2 seconds only. I have changed the oil with synthetic 5w30 and a Jag oil filter. Still does it. The best I can surmise at this point is that the noise is coming from the top front of the passenger side valve/cam cover. I am assuming the worst and that it is either a bad vvt unit or cam chain tensioner, but how do I tell which?

I spoke with the head local Jaguar tech yesterday and he said to run it through a couple of oil changes to see if it gets better due to the having been in storage. Sounds like this would be to easy a fix.

Any help would be greatly appreciated and thank you in advance.

 

Very unlikely to be the cam tensioner on your engine, this issue was fixed before the X350 cars came out, but obviously worth a check at some point.

It could be the electrical connection to the VVT oil control valve solenoid. The system relies on a pulsed signal which allows the valve to take up any position between full retard and full advance. Other thing that effects it is the input from the camshaft position detector. This feeds back cam position to to the ECM so it can calculate the pulse signal correctly. The solenoid feeds oil to both sides of a vane device which moves in a vane chamber up to 48 degrees.

Other thing is that if oil drains out of the vane chamber on one or other side, you will get metallic contact, until oil pressure recharges the chamber. Of course this should NOT be happening !!

The part that could be causing this effect is the "VVT stopper pin". This locks the VVT in a fixed position on shutdown until oil pressure has built up to force it open. If this is sticking, it could be failing to lock the VVT, hence the clacking when you start the car. The VVT does not operate until oil pressure exceeds 1.25 bar (about 22 psi)

Complex, isn't it !!

 

Ok - thanks for the info on the system and operations. It makes sense but what I still don't know is how to test or narrow down the culprit. Can you help me with a logical way to systematically find the bad part? Once again thanks in advance.

 

First off I would disconnect/connect the plug on the VVT solenoid and also check the pins for corrosion. Bad connections can play havoc with electrical functions.

Other thing is to read off the stored fault codes, (if any). I would expect the system to detect anomalies in the system. However, I suspect you will find nothing.

If the VVT locking pin is sticking then this won't throw up a fault. As the noise is only one bank of cylinders, it sounds like the locking pin may be sticking on that side. As the dealer says run the car for a bit, and change the oil, and the pin may free up. There is also no harm in looking at the cam chain tensioner for peace of mind, although as I said, the X350 engine does not normally suffer, unlike the previous V8 engines.

As the rattle is only 1-2 seconds on start-up, I am inclined to point to the VVT locking pin as the cause. Oil pressure forces it off its seat on start-up so the VVT can start operation. If the VVT is not locked on start up, the vanes in the unit could clatter against the housing until oil enters the VVT under pressure, and this will take about 1-2 seconds.

 

Fraser - thank you for your knowledge. A couple of questions 1 - what if anything should happen if I unplug the VVT solenoids with or without the car running. I will obviously check and clean the connectors. 2 - can I check for codes with an OBDII unit or does it need to be checked by a Jag service center? Thanks again.

 

Hi Blake. I'm not a Jaguar techie, so cannot answer these two questions, but I would carry out any disconnect/connect with the engine shut down. All you're trying to do with this is remake the metal-metal connection which may have built up corrosion causing a high resistance, hence less volts gets to the the component supplied by wiring.

As regards OBDII, hopefully another expert will reply. What usually happens is the code value is read OK, but the reader unit cannot translate this to text because it is a Jaguar-specific code.

 

I would go along with what Frazer has stated and adding that don't be tempted to use cheap oils with these engines.
A good quality 5W40 semi synth is reqired.
It would be interesting to know how long the car has been in storage.
This wil also determine the condition of the battery which in these modern vehicles is of vital importance.
These cars as do most modern luxury cars place great demands on their batteries.
As the 'noise' only lasts a second or two, it doesn't really sound like something to worry too much about.
I would suggest a good 'Italian Tune Up' before worrying unduly about a small noise.;o))
Most certainly clean as many connetcors that are accessible with contact cleaner/lubricant sparay....especially as many earth points as you can find.
Disconnect the battery while doing this and make sure you have rodio codes before hand.
You will be surprised by how much better it can be by cleaning a few contacts.
Removes many a 'ghost' problem.
Have your battery rested properly for it's condition as it will possibly be loosing it's performance if it is original.

 

Yes I have that sound too when engine is cold. I have always ignored it thought it was the purge valve but the sound is only there when the engine is cold and it come directly from the engine - so I properly also have this issue. Where are these VVT pin connectors located on the engine?
Thank you in advance
Martin

 

I have been listing to the engine. I believe this car has solid lifters - could this just be metal to metal noise until oil has reach the top? I will try a different oil because this started when I switched to Mobil M1 - maybe a class 4 oil(real synthetic oil) will help, BTW never have had this noise with Castrol euro maybe I should just go back

 

Entertaining thread

 

where do we unplug this vvt to see if that is the problem? I have a tap tap tap at cold start and it goes away if I push the accelerator up to 1500 rpms. It will come back after a bit if idling but is gone during drive. Can we leave this unplugged and just drive it like that if the noise dissapears?

 

Blake. Quite a few years ago I bought a lovely Saab 9000 with only 30,000 miles on the clock and I had a similar sound on start up.
Instinct told me it was the hydraulic tappets, one of which was draining on standing. As far as I remember it just "went away". They are the best type of faults!
Hope you liked the story!

NB I don't know if the tappets are hydraulic on this engine.

 

I would think the oil is draining down overnight or there is a partially block oil passage from build up. I would start with an oil change with a filter you know has the anti drainback valve (someone will chime in I forked over $20 for a genuwhine jag filter). I would then run the car up to temp and drive around and see if it repeats the next morning. If so, then look at some other issues. FYI my rover (I know not the same) does this with synthetic if i let it sit a few days and has for 50k miles.

 

My car did this too, when I bought it. The dealership changed the oil and put full synthetic in it. My mechanic at Motorcars LTD in Dallas said that was a big no-no. Told me to go ahead and run it for 3K miles, change it to regular Castrol GTX 10W30 and see if it's not any better. Told me to go back to 5W30 on the next oil change. It's not quite as bad as it was, and it's making less racket on startup, so I think it's working. Anxious to see what it does on the next oil change.

 

What a load of old cobblers!

Your mechanic is having a lend of you or know's jack s**t about these engines!
A top quality synthetic 5W40 is the way to go.
Depending on ambient temps....no more than 10W50.
Other than this, I would say the engine needs a jolly good flush with flushing oil, drain and fill with quality oil and give it a good run for at least 100 miles.
Most of these perceived problems are created through lack of use.

 

This sounds very similar to my current problem. Was the noise ever resolved?

 

Yes - it did in fact turn out to be the Variable valve Timing unit. It is a big job but not impossible. I would recommend a whole lot of research before tackling it though. Lots of tough spots to deal with - one being the ac compressor, another is having all the correct tools. Good luck, if I can be of help I will.

 

Nice to know my original prognosis re VVT unit was correct !

 

Can you elaborate a bit more on exactly what the issue was with the VVT, what you did to repair it, and approximate costs. I'm having a similar issue, so I'm assuming my VVT may be faulty as well.

Are we talking more or less than a $1,000 repair here?

 

Ok, here we go -
1 - dealer quoted $3000 to do the fix and included all new timing chains, tensioners and both VVT units.
2 - cost me around $700-$800 for all parts and materials/tool rental (note I only did 1 vvt, 1 upper tensioner and one timing chain on the passenger side of the motor)
3 - some suppliers offer a complete kit for this job incl. all the chains, tensioners, vvt units,gaskets etc
4 - I was able to diagnose the noise to passenger side of motor by having someone start the car with me listening under the hood at first start up (meaning anytime the car sat for more than 2 hours between starts. You can get a cheap mechanics stethescope at Harbor Freight and listen to this unnerving clatter at the top front of the valve covers near the vvt solenoid connector.
5 - Note that I tried all the different weight oils and filters including factory stuff and the problem was only getting worse. Root cause of the problem is that the VVT unit losses its ability to hold oil pressure at shut off thus drains back and needs to rebuild oil pressure to operate correctly and quite.
6 - my car had about 40,000 on it when I fixed it and now has 53000 with not a singe noise since repair.
7 - quick overview of repair incl drain antifreeze/oil, remove all belts,hoses and electrical connectors, remove radiator, remove crank pulley (better have good compressor and air gun), remove valve covers and timing covers, remove ac bracket (NOT the compressor or you will need to have system recharged) this is a PITA its tight in there.

Good luck - let me know if you need anything more.