Question: Engine - funny noise

[Uwe]

Hi all
my GT 1900, 100.000 km (orig. engine) does make some strange noise sometimes. It sounds like a rattle in the area of the gas intake if I let gas back to 1000 - 1300 rpm. Higher rpm's it disappears.
It is the same with cold or warm engine.
First I thought its some hose clamp ticking the gas intake - I tied everything away - noise continues
It appeared still if I unmount the V-belt (so waterpump and generator can be excluded)
someone told me, that it could be the chain or the chain guide rails
I replaced the chain adjuster (tensioner) with a new one already - noise continues
Could it be just a screw that fell in the air intake and stays there and at a certain resonance frequency it start rattling?

Any ideas?
Uwe

[Gary]

Just a thought... There is a heat shield on the passenger side frame rail. The exhaust pipe runs right next to it. If the shield came loose, it might vibrate and hit the exhaust pipe.

[Uwe]

Hi Gary

thx for that fast reply!

Yeah I examined that heat shield already - found lots of missed tools inbetween shield and body (:-).

Will check the exhaust pipe next on Saturday - great hint.

As I think 100.000 km the chain shouldn't be damaged.

Keep you updated

Regards
Uwe

[hrcollinsjr]

While you're underneath you may as well check the shield on the front of the bellhousing.

You may want to check further back on the exhaust system as well.

Harold

[krewzer]

I found a curious rattle while revving the engine, at the carb, with the air intake removed. With the choke off, or engine warmed, and at a certain rpm, the choke plates would rattle and chatter. Makes a curious sound, sort of like your valve assembly has worked itself loose. I've heard it while driving, and pushing thru first gear to second. Makes you feel like backing off a bit. But hell, if it breaks, I'll be the only one around that can fix it. I was happy to hear that the culprit was a harmless, harmonic vibration, of sorts.
Wes

[tekenaar]

Originally Posted by Uwe Hi all my GT 1900, 100.000 km (orig. engine) does make some strange noise sometimes. It sounds like a rattle in the area of the gas intake if I let gas back to 1000 - 1300 rpm. Higher rpm's it disappears. It is the same with cold or warm engine. First I thought its some hose clamp ticking the gas intake - I tied everything away - noise continues It appeared still if I unmount the V-belt (so waterpump and generator can be excluded) someone told me, that it could be the chain or the chain guide rails I replaced the chain adjuster (tensioner) with a new one already - noise continues Could it be just a screw that fell in the air intake and stays there and at a certain resonance frequency it start rattling? Any ideas? Uwe

. . . but I had a very similar noise under similar conditions in my first GT's engine many, many years ago and eventually found it was caused by this . . .



. . . oil pressure is lower at low RPMs resulting in lower tensioner pressure against the chain and causes the chain to slacken just enough to rattle the loose upper chain guide intermittently against the inside of the timing cover.

When the engine is revved beyond the point where it rattles, the oil pressure is sufficient to keep the chain taut against the upper chain guide to keep it pressed against the timing cover and the rattling stops.

Took me quite a while to find it in 1978!

[Gary]

That photo shows the "new improved" version of the small chain guide. The older ones were made of metal with a rubber coating like the long fixed guide.

[tekenaar]

Originally Posted by Gary That photo shows the "new improved" version of the small chain guide. The older ones were made of metal with a rubber coating like the long fixed guide.

True, I had the problem with the original version, but this is the only pic I had of the problem area . . . I don't think you'd have any noise with the new version, even if it came loose at the bottom! . . . the rubber would likely cushion it regardless . . .

[Uwe]

Hi Otto, thx for that message but unfortunately I couldn't work on the car long time. It turns out that most likely the source of the noise is the chain.
Do I really have to remove the Cylinderhead and oilpan for removing the timing chain cover damper blocks and the chain?
Thatwould be horrable lot's of work ....
Uwe

[opelnut10]

Originally Posted by Uwe Hi Otto, thx for that message but unfortunately I couldn't work on the car long time. It turns out that most likely the source of the noise is the chain. Do I really have to remove the Cylinderhead and oilpan for removing the timing chain cover damper blocks and the chain? Thatwould be horrable lot's of work .... Uwe

If you can find a timing chain with a removeable link in the chain you can change it out without removing the head.

[BQS4]

Originally Posted by opelnut10 If you can find a timing chain with a removeable link in the chain you can change it out without removing the head.

There's a timing chain that goes to a MB motor that's exactly like the Opel's (double row) It's just a little longer, but, has a master link. I don't know the MB number, but, I'll try and look it up.

[Uwe]

Thx for hint, But I need to replace as well the damper blocks.... so the chain with a lock is not the solution - I am afraid