Folks,
I've just replaced the timing belt on my excellent 2.5 XM estate. 142K 1997. Nothing beats it for load carrying and motorway cruising...
The injector nozzles were replaced, and I've now got an interesting "London Taxi"-style classic diesel knock below 1500rpm.
It runs fine and the noise disappears above 1500-1750rpm. Yes, the timing is correct... :-)
I'm wondering if refurbished injectors (with new springs?) and a new belt (tensioned correctly) have set up an odd resonance. It does not go away when warm
Please don't tell me it could be worse.....
Does anyone have similar diesel experience they could share? It will be taken back to my local diesel specialist (long-established, and highly experienced) for their sages to have a listen today...
rg
Edited by Pugugly on 23/05/2008 at 18:19
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I have been running td XM's for the past 12 years or so, but of the 2.1 variety so cant help a lot as the 2.5 as a completely different animal. Take a look on 'club-xm.com' there is a whole section there devoted to 2.5's and many devoted owners.
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Hello Peter,
Yes, I seem to be dominating the 2.5 section over there at the moment.... !
It's been a campaign of work over five days, mid-life service-ish stuff such as timing and balancer belts, large radiator, two sections of exhaust, a bit of retuirn pipe, front tyres, accumulator sphere, and the injectors.
Now, the noise has come as a bit of a blow. Maybe I'm just tired...
rg
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Sorry! I just noticed your post. There doesn't seem to be much activity there at the moment. That's where all the experts are, one should be along in a minute.
I would say from general experience with diesels that you have a faulty injector. The usual way to isolate it would be to slacken the the fuel feed pipe to each injector in turn until the knock stops, that always worked with machanically governed pumps, although you will have to hold the throttle open a little to stop it stalling. Whether the electronic involvement will interfere with this method I dont know.
Sorry I missed your previous posts, I tend not to look at the 2.5 section as I cant usually help much.
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Yes, it's quiet at the moment.
I'm now tending towards thinking the balancer shaft belts is still too tight, even though it it "90 deg. twistable". It's got quite coarse teeth, which could do a passable impersonation of a diesel pump.
Anyway, I'll whip the covers off yet again, and take a look. With a first-time change on any vehicle, it's always a bit of a voyage of discovery.
r
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Noz is the chap, but I expect he is busy again at the noment. You see why I like 2.1s !
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Hmm... that's a big debate...
Have you ever driven a 2.5? Chunks and chunks of torque....
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Yes have and a I liked it, especially the light clutch, but I couldn't cope with the hassle of trying to work on one and find spares for it - and they dont seem to be as durable as the 2.1.
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The knocking is the new injectors. I replaced mine in a Merc diesel at 180k miles; after 10k miles they have quitened down a lot -still not quite back to where it was but not far off. Dont know why this happens - just does. Drive it a lot it will get better.
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Thanks, all!
i retensioned the balancer shaft belt yesterday, and some of the noise,and all of the whine, went.
There's still a pronounced knock, but the engine runs fine throughout the range. I rechecked the timing, which was spot on.
rg
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The noise turned out not to be pump/injector related, but the stud holding the tensioner roller being loose enough to rattle and set up resonance on the belt which did an uncanny impersonation of diesel knock
Loctite on the nut had fused the roller to the stud, so, remarkably, the tensioner nut would tighten up OK, but the stud remained loose.
The motor is now utterly sweet - i was beginning to dread some pump/lift sesnor.injector hassle. Phew!
The root of the problem was the indie having over-tightened everything when they last did the belt, including stripping the thread on one of the engine mounts. I had to take a deep breath when dealing with the tensioner nuts, as I felt sure that the threads may have been damaged.
More reassurance for me that, despite this campaign of jobs becoming a real epic, I'd rather have the reassurance that working on your own vehicle brings.
Meanwhile, I played a little game with the trip computer this morning, resetting it before a run down a long dual carriageway for thirty miles. I managed to get 44mpg average at a cruise of 75mph indicated....
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