Strange rattle starting from cold

[drjonts]

Well Wes, I think I might have to seeing as yesterday in a moment of madness I brought home a project (not MG/Rover)...

...a 4.2 Jag XJ8 with a rear ABS sensor issue that would have gone to be parted out otherwise! I couldn't leave the poor thing to such a fate. Wafted along the 50 miles home in squishy seat luxury and it didn't miss a beat other than the dash telling me it had an ABS fault and no stability control.

I think I will just have to be brave, thorough and pragmatic and give the cambelt a go. I'll try and keep you all posted as to how it goes.

Jonty

[drjonts]

Hi folks,

Hope everyone is keeping well during these strange times.

The XJ8 I picked up took my car repair focus before we got into all this lockdown so I had wheels with the ZT-T being poorly. After grabbing a LR/Jag code reader I was able to identify that it needed a new wheel speed sensor on the rear which would cure the ABS and limp home issues with the gearbox as it couldn't tell what gear ratios it should select. I also found the engine light was on because of a failing heater on one of the lambda sensors on one bank. So a new one of those cured that. A few droplink / stabiliser boots to renew on the rear and a set of pads on the back and it flew through the MOT with zero advisories! Happy with that so I have been wafting about in V8 comfort of late...but only to get food from Sainsbury's!

As I have at last managed to give garden and hedge clearance duties a rest and found the drive to clamber about under the ZT-T, I thought I should update you on where I have got to with investigating the flappy cambelt issue I've had on the V6.

Armed with a Gates tensioner spring / piston unit for a Landy (different design from the original but I guess Gates should be OK) I set about stripping the front of the engine down yesterday / today along with helpful notes from you lot and Mr Haynes' finest literature. After numerous pauses for coffee and biscuits and plenty of prevaricating about the bush I finally got on with it and despite finding some tricky bolts that were fairly tight and the awkwardness of a sloping drive making supporting the engine a pain, I eventually had all the covers off the front belt to have a look at the tensioner pulley, carrier and piston.

Sorry if images are big...and a bit blurry - focus is tricky at such close quarters!





The tensioner pulley bolt doesn't appear to have come loose in service...everything tight there with a well adjusted eccentric position with clearance between pulley and carrier and the 8mm hex key hole is near to the expected 4 o'clock position for a well set pulley. So when I had the belts done less than 25k miles ago it appears to have been set properly there.

Hydraulic/spring tensioner piston looks to be the original one with surface rust and a stamped date of 01/05/01 on the side plate (I assume that is 2001 and fits with the car's age having a 51 plate). Before swapping anything I inserted a hex key into the tensioner pulley adjuster hole and was able to increase and decrease the belt tension - the piston would just sit where it was pushed to. I put a 1.5mm drill bit in the piston to lock it, set the crank to the safe position, pinned the flywheel, checked the rear pulley marks were where they should be and added a couple of Tipp-Ex marks on the front belt to make sure things didn't shift. I rotated the tensioner to tighten the belt with the hex key and an extension tube and wedged it in position with a long spanner butting up against the bulkhead to keep the tension on the belt whilst I removed the hydraulic tensioner.

It came off quite easily and I swapped it for the Gates one with a spot of threadlock on the bolts. Tightened up, released the hex key tension and then pulled the pin on the piston.



The Gates tensioner when pinned seemed to be shorter than my old tenioner by 1mm - 2mm so I expected it to push out a little further when released which it seems to have done. To make sure tension was on the belt I once again put the hex key in the pulley, tweaked it to tighten the belt and watched the piston move out slightly as I did so. I then tried to push the tensioner back against the piston like I did with the old one. Things appeared to feel more solid this time, more resistance to retracting...perhaps the new tensioner piston is doing the job better now?

I didn't want to slack off the tensioner pulley bolt and try to tweak anything further so I simply left it all where it now sits and checked the belt tension with my little mechanical FACOM tool. Seems the belt tension is where it would be for a new belt right now. So I tried to push the tensioner back with the hex key and watched the FACOM gauge move about as I did so, but it settled back in place when I stopped. My gut feeling was a belt on just under 25k miles might have seen the tensioner extend slightly so it's a decent start point now. Anyone think I should adjust the eccentric a little to retract the piston slightly and re-check tension or just leave as is and test?

At this point bad light stopped play and I tidied up seeing as we may get some rain tonight and very likely tomorrow. It's not all back together and I'd love to run it while everything is stripped down to check it works OK but not sure how the car would like running without being all back together and no covers on the belt seems a bit scary! So I guess I'll put everything back, run it and see what happens - running the engine with the previous tensioner just saw the piston retreat back in when it had been dynamically loaded. Only a run and heat cycle will tell me if I have this fixed for now.

Will report back!

Cheers,

Jonty

[drjonts]

Evening Folks.

Updates...
Well, I have put everything back on the engine bar the top cam pulley cover nearest the bulkhead so I can check what's going on with the belt and watch for flappiness. I have now started the car 4 times from cold and I don't have the knock of 'belt on cam cover' from cold.

The belt tension does still increase as the car warms up and the belt definitely tightens as it is clear to feel when I stop the engine and poke the belt to check the deflection. When cold the tension seems to relieve a bit but not to the point which was worrying me. It seems that what I have done in replacing the hydraulic tensioner but not touching any other tension adjustment appears to have made things better - I am somewhat relieved that this is the case and I am now much more aware of what might go on behind those front covers.

When the timing belt job was done 23k ish miles ago it appears that I received a Contitech front belt...but Dayco rear belts. I assumed that a Contitech sticker on the engine cover meant that was the belt 'kit' that had been fitted. I hadn't realised the rear belt was Dayco until I turned the motor over and spotted blue printing on the back of the belt. The tensioner pulley which was put on is INA but I didn't ID the waterpump or idler pulley. It appears I have a variety of manufacturers in the timing belt train now - not a belt and pulley 'kit'. I only opened up the rear belt cover towards the front of the car to check alignment of things and there is some slack in the used Dayco belt but not sure how much deflection should be expected after 23k miles...anyone have any sage advice to get a measure on that or check?

So I am wondering about just getting a full set of timing belt goodies and tackling the job in due course. I know it's only been less than 25k miles so far but that way I will know what has been put on the car. For now, it appears that things are better so I will give the car an oil and filter change while the undertray is off. The auxiliary belt is an original Rover one and I've put it back on to get things running but a few cracks in the ribs (including one crack that is across all the ribs at one point) means I think I should probably change it. With all the front mounts to get off just to do that I'm halfway to a timing belt change eh!!!

I still have some 190 brake calipers to refurb, a new aircon radiator, a new rear anti-roll bar and links to put on and cam cover breathers to check...but more pressing is a clutch release bearing whirr to assess! Will let you know of the developments but fingers crossed things are tickety boo for now.

Cheers all and stay safe.

Jonty