Chain Tensioner Failure (Loose Alternator Mount)

[n9lri]

Hello

72 with 51150 miles

All of a sudden have rattle at 2400 rpm and above.
From front of engine. Truely sounds like chain against timing housing.
Runs fine at idle and up to 2000 rpm, no noise at all.

Ok car has been siting for a while so is it possible that the tensioner is stuck or broke ? GM book is poor on info on this one.
States that adjuster is driven by oil pressure but isn't there a plastic arch above the oil driven tensioner. ? And what about the slide on the other side ? they ever fall apart ?

I guess the real question is What breaks and lets them make noise.
P.S it looks like the cover has been off before. < Lots of RTV >

Thanks
Neal

[nobody]

oh ya they do fall apart, it is not pretty but it does happen.

[kwilford]

Probably the tensioner plunger has failed or seized. I think you can screw it out the side of the chain case and inspect it. I haven't done it yet, but there is a "fix" where a spacer (an old brake cylinder piston) is added in between the plunger and the tensioner, to make up for a stretched chain. I believe Otto has created a diagram to describe the fix. Otto?

[GTJIM]

The actual oil pressure actuated adjuster can reach the end of its travel when the chain link pins wear and the two short tensioner "rubber" buffers get grooves worn in them. The long damper is on the drive side of the chain and only damps out flapping from the chain and does ont have anything to do with tension as such.

A Quick and Dirty temporary fix is to undo the 19mm hex on the timing cover that is the outer end of the adjuster and removing it. Then extend the inner end by placing a slide on cap over it that lengthens it by about 6mm to 8mm.
Before reinstalling it just check how much slack there is in the chain by pushing on the buffer the adjuster rides on to see how much it moves.

The adjuster is spring loaded so make sure the cap is not so long it prevents the tip moving in and out. Also make sure that the oil does not have ground up bits of the buffers in it......

Eventually you will have to remove the front cover and do it all properly with a new chain and damper kit plus a new adjuster - but the Q & D fix may keep you going till you can chase up the parts.

[oldopelguy]

I've had the little plastic button on the end of the cam fall out and make the same rucus as well. Might be worth a look.

[greensmurf20]

look at the alternator bracket bushing. the mount is mounted in rubber on the front of the timing chain cover, its hard to explain without a picture. the rubber bushing on mine was rotted and finally fell apart, and made a noise i thought was the timing chain slapping at anything above 3,200 RPM. check that alternator bracket bushing, that was the cause of my noise, i swore it was the timing chain at the time.

[kwilford]

Here is the tensioner "enhancement"

http://opelgt.com/forums/showthread.php?t=2959

[tekenaar]

Probably the tensioner plunger has failed or seized. I think you can screw it out the side of the chain case and inspect it. I haven't done it yet, but there is a "fix" where a spacer (an old brake cylinder piston) is added in between the plunger and the tensioner, to make up for a stretched chain. I believe Otto has created a diagram to describe the fix. Otto?

Here's the fix in Tips and Tricks.

[n9lri]

Hi Guys and thanks for the replys.


My first test is to take off belt to make sure its inside the motor.

Since this car has actual 51000 I cant believe the chain is shot < but I could be wrong > My hunch is that one of the plastic parts has crumbled.
I hope its the plunger stuck.
I did check the cam button its there but pretty brittle, and cover shows shiny spot so its making contact. < I wondered if cam gear was loose but no it was tight >

I will check alternator and plunger later today.
My father purchased this car back in late 70's. He passed away in 92 and car has not been driven since 94. In fact its not been driven more than 2000 miles since it was purchased.

Shes a garage queen but at least it was a warm and dry garage.

I had to rebuild front calipers < stuck > and blow out carb, rewire headlights and thats it. Runs fine but noise is a bit much. I do have complete spare motor to rob from if need be.

Now from what I see that cover will come off with out removing head and looks like on this car it has been done by the amount of Rtv sticking out all around it. So someone has been in there before and didn't get the job done.
From that I have to wonder if its very possibly the alternator.



Thanks
Neal

[fredopelgt]

Yea! however, they do wear with deep grooves, if we take it that the car has only done 50 miles per week that have a reading of 78000 miles. I would suspect that it actually has a 1 infront of the mileage. If you allow the slap to continue you will drive the chain through the cover and you do not want that to happen! Been there oil everywere in the engine bay and a blown engine. Cheaper to investigate fully! wish you the best of luck.

Its only money that keeps your GT running.

[nobody]

To get the cover off you will be pulling the pan. You can get the cover in without removing the head but you will be using even more RTV to try and get it to seal back up. There is a rubber ring that goes from that cover to the water jacket in the head and it would be very hard to get it in right and have it all seal up. If it were me I would pull the head and have a new gasket set on hand. In doing this you will be disturbing almost every gasket and seal in the motor so it would be cheaper just to get new and be done with it.

[n9lri]

Thank you for all the feedback

It was the alternator. The top bracket grommet was gone and from the looks of it for a long time.

Found new grommet and worked to get it together tight and No Rattle at 2400 anymore. < This really does sound like the chain loose ! >

Bad news its been loose so long has caused small crack in mounting point.

No oil from it just crack but it tightened up ok so we will see if it holds.

Thanks guys I'll be around here a bunch.

Neal

[tekenaar]

Thank you for all the feedback

It was the alternator. The top bracket grommet was gone and from the looks of it for a long time.

Found new grommet and worked to get it together tight and No Rattle at 2400 anymore. < This really does sound like the chain loose ! >

Bad news its been loose so long has caused small crack in mounting point.

No oil from it just crack but it tightened up ok so we will see if it holds.

Thanks guys I'll be around here a bunch.

Neal

Remove mounting bolt, clean up area around crack, mix up and apply some JB Weld and work into crack and surrounding area, let sit for several hours and reassemble . . . PERMANENT FIX!

[garrymc]

Thank you for all the feedback

It was the alternator. The top bracket grommet was gone and from the looks of it for a long time.

Found new grommet and worked to get it together tight and No Rattle at 2400 anymore. < This really does sound like the chain loose ! >

Bad news its been loose so long has caused small crack in mounting point.

No oil from it just crack but it tightened up ok so we will see if it holds.

Thanks guys I'll be around here a bunch.

Neal

Good one Jared(greensmurf20)!

[kwilford]

If the top alternator mount hole in the aluminum chain case has worn (VERY common), sometimes it can be repaired by drilling it a bit oversize and inserting a short length of steel tube from the front with an internal diameter suitable for the top bolt. That worked with mine, although it hadn't worn enough to actually crack or break the case (I don't recall where I found the piece of steel tube). But a word to the wise. It usually wears because the BOTTOM alternator bracket has become loose. Make sure that BOTH bolts that attach the bottom bracket (front one goes into the chain case, rear into the block) are secure. If the bracket has been loose, the front mounting on the chain case will be worn, as might be the bracket itself. If the bracket is a cast iron version (more typical in the Manta/Ascona, I believe), the bracket will be OK, but the mounting "flat" on the chain case will be worn such that it is impossible to get the bottom bracket to line up properly. I had to grind mine flat, and then install a large washer between the bracket and the case to get it aligned properly.

JM2CW

[greensmurf20]

glad to hear you got it fixed neal, always nice when its something simple

[jvandyke]

Here's the fix in Tips and Tricks.

If I'm reading above diagram correctly:
Looks like the "dished" interior of the piston needs to be drilled out? Any idea on which size bit? Would you need to use a bit with a flat end (not pointed) to achieve this? Is there such a thing?
What about a brass pipe end cap?
I'd like to take a crack at making the cap before I even take out the plunger.
(after I check my lower alt. bracket)

Is this the same thing via RallyBob? Looks like he made his own cap.
http://www.opelgt.com/forums/14168-post48.html

[GTJIM]

TRW also supplied replacement tensioners so 10 to 1 there are different diameters of the tensioner tip due to 'metric' conversion specs. I would suggest that you measure the exact one you have!

Yes, the inside does need to be turned out with a flat bottom hole to fit and Yes, the picture that Rally Bob posted is the same thing with a hand made cap. Note the oil hole he has drilled through the end to help oiling too.

The inside needs to be turned to size on a lathe - just drilling with a flat ended drill (yep - they do make them) may not make the cap nice thumb-press fit on the tensioner ... you DON'T want the unprintable thing falling off and ending up down in the timing chain .... somewhere!
I think R. Bob made his out of steel and tacked it on with a couple of zaps of TIG weld.

HTH

[jvandyke]

Good thanks, I actually have a 1948 Shopsmith and it can be a lathe. Good excuse to try and figure that one out!!
http://www.owwm.com/PhotoIndex/detail.asp?id=2707

[jvandyke]

I'm comtemplating taking out my tensioner plunger just to eyeball what's up in there, possibly come up with an extender of some sort (I found my old rear wheel cylinder so I can scavenge some pistons, I love it when I keep junk and it becomes useful!).
I thought I saw a post somewhere where someone was grateful nothing came apart when pulling the plunger. Is there a potential for something nasty to happen when pulling this guy out?