While at the Hagerty Young Drivers Experience last weekend I noticed an intermittant little rattle coming from the engine. Came and went. Drove home with no problem and got around to troubleshooting today.
I isolated the noise to the timing gear. On pulling the cam covers I found the upper left chain damper had sheered off. just above where it’s bolted to the block and the broken piece was sitting loose in the engine. No apparent secondary damage. This aftermarket piece was part of a large kit I purchased from my usual supplier when I rebuilt the engine 6,000 miles ago. This is a pic of the broken piece with the original piece in the background:
Anybody have an idea how this would happen after 6K miles? (see footnote #1) EDIT 2: Failure mode was not sheer but fatigue
replacement possible without pulling the head and the timing cover? (looks to me like pulling the timing cover alone would provide the needed access EDIT: the answer’s yes. Sump, damper, water pump, timing cover. Still trying to figure out failure mode.
As the function of this piece is to quiet the sound of the upper chain, is there any potential for damage by driving the car until I can get around to the fix? (see footnote #2)
Footnote #1: This damper was installed per the manual, just kissing the chain. The chains themselves I would have to say are still perfectly tensioned, not dead tight but with a little bit of slack. The shoe on the replacement damper is quite soft - I can depress the rubber with my thumb
Nick
They don’t look like the same beastie. The original is retained by an oval shaped piece of metal completely surrounded by the rubber material . In the photo it looks like your replacement part has a completely different mounting/supporting system. Possibly the original has more inherent flexibility from the active face to the rigid mounting points at the bolts???
Matt
The pieces are shaped the same, Matt, it’s a matter of quality. The original Metalastik part has more of the rubber material bonded to it over a larger area, but the thickness of the rubber in the extended area is minimal. It’s that oval area of bare steel plus the right angle above the leftmost bolt hole in the top pic that’s busted off and still bolted securely to the block.
I’m wrong saying this was sheer. On looking more closely at the piece it’s clear the failure mode was fatigue. The chain slaps into this damper. If it flexes even a little bit it will set up gradual fatigue at the weakest point, in this case at the base. This eventually caused a crack to form at the crotch of that right angle that gradually proliferated upward. Cheap, aftermarket junk part.
Can you post picture of the part still bolted to the engine, hopefully with flash or good lighting?
If it is fatigue then it has been flexing. To do that it would take fairly heavy bending loads for such thick steel over such a short distance from mounting point to leverage point (where chain rubs). The chain rubbing has clearly not been wildly excessive judging by pad rubbing marks, although it has worn a bit at the tip which is the furthest point/highest bending load from the failed end.
The other loading glitch would be forgetting or mis-mounting the 4 spacers and the steel strip guide underneath and between them?
Yes…that’s what I was talking about. They look the same but the load path from the rubber surface to the fixed bolting position looks different. Metalastic know how to design compliant bushes of all types…and there is a lot of technology in their various designs…but the aftermarket part was made to fit in the same position without enough consideration to the function it had to perform. Annoying.
Hi Nick, that’s a bummer. I suspect you could drive it until you fix it. Picture below is from my Mk2. One prior “mechanic” didn’t release the spiral ratchet. Lots of wear on the post and noisy at idle - but clearly running loose for years. You upper would present less risk, I’m sure. Paul
One thing that jumps out at me watching the video - the “good” part has a nice, radiused bend, while the “bad” part has a VERY sharp bend. That, alone, could easily explain the failure, as such a sharp bend would almost certainly lead to internal fractures before the part ever gets close to the engine. I see what appears to be a pre-existing fracture in the middle of the bend, which would confirm my suspicions. Can you post a close-up picture looking straight at the surface resulting from the fracture?
How’s this? About as close as my camera allows. Notice how straight and clean the fracture line is at one end and how ragged it is otherwise. Leads me to suspect there was a crack in the part at the beginning of the sharp 90 degree bend.
It appears to me the bend was likely fractured, at least internally, which allowed the rest of the plate to flex a lot more than it should, which led to fatigue failure. I think there is no question that was a truly cr@ptastic part…
I’d see if maybe Dick Maury can either sell you a couple of good parts, or tell you where he buys his. I’d also send yours back to the owner of whatever vendor you bought them from, along with a strongly worded letter.
The marque specialist that rebuilt my 3.8 sent all my guides out to be refurbished - somewhere in Sydney. They came back with a surface, similar to the original bonded to the old brackets. Would expect you could manage the same in North America?
Great idea, Breen. I had my XK120 brake shoes refurbished but it took 6 weeks. At this point thinking about turn-around time.
Yup. Not going to drive it as is. Will begin the teardown in the morning.
I’ll be in touch with the vendor if only to give them a heads up. They’re one of the bigger outfits so likely have sold several of these little time bombs and may want to warn their customers who bought and installed them. What do you think are the chances? But I will indeed need to source better replacements. Much as they look good I’d rather not reinstall the 49-year-old original dampers.
Update:
(I’ve just noticed I’ve been spelling “shear” wrongly).
I’ve been in contact with the supplier/owner who has advised that they’ve sold around 1200 of this particular part (C13616) and have had no similar issues reported. However, he’s taking the matter seriously and pledges to get to the bottom of it - I fired off some additional closeup pics his way and he’s having his engine expert take a look. At first blush it appears, as already put forward, to be related to a manufacturing flaw in the radius of the bend together with normal destructive harmonics in the engine. More to come next week when I hear back. I have had mostly very good experiences with this company.
So I got on the phone this morning and called a couple of fellow local E-type owners and one of them offered a brand new set of upper guides from the very same supplier. I’m not impressed with the quality so will not use them. The dampers are supposed to be mirror images of one another each with a precise 90 degree radius. Look at these pics; on the left is the original pair laying flat on their shoes and arranged flange to flange, and beside it the new aftermarket pair arranged the same way for comparison:
See the differences? More material on the originals. The shoes on both originals are precision fits while one of the aftermarket items has 3/16" of steel protruding at its top end. The original shoes also feature what I think are shallow grooves to channel oil while the others don’t - I’ve no idea if this makes a practical difference but suppose they were put into the originals for a reason.
What you can’t see is the hardness of the material. The shoe on the busted guide above is fairly soft while the shoes on the new aftermarket items are fairly hard, but not as hard as shoes on the originals. What I don’t know is if the rubber on the broken, used item has softened from oil saturation or if the originals have hardened with age.
So, I’m on the lookout for Metalastic items. I’m advised that the car’s ok to drive so long as I keep the revs down below 3500 or so, so that’ll give me a little time. If I’m not successful I’m thinking seriously of reinstalling the originals as they’re in great shape.
Nick
The quality of the aftermarket parts is terrible… Especially when you display them as you have to illustrate the terrible geometry…not fit for purpose!!
I would put the originals back in. The chain links run in the grooves on the face of the damper and the chain rollers run in between so it is a “nice” running condition…they wear in before they wear out…so to speak…and they are not heavily loaded…just taking the whip out of the chain at certain engine speeds…
Regards
Matt
Ignorance is bliss, Nick, and your thread here is making me nervous. I had a similar problem with one of my lower guides when I did my rebuild in 2013. As it came from one of the usuals, the guide on the lower right of the first picture didn’t sit flush against the chains. I was able to bend it slightly to make it fit flush and 11,000 miles later, I think everything is still OK because I don’t hear any ominous noises from the front of the engine. Still…
Looks like you succeeded, Mark. That lower guide is more robust than the uppers, the way it jogs to the outside then doubles back toward the mounting. It’s got a lot more steel in it. I think you can sleep easily.
That sharp line along the bend is just asking to cause a fracture. If there are 1200 sets of those in circulation there are some engines that are in danger of failure.
