New timing belt. Slight surface blistering normal?

bebbetufs · bebbetufs's Garage

My new gates belt, (tensioned with the arnnworx tool) has been through one heat cycle. I am running with the covers off to check for issues before installing them permanently. I notice that there is some slight surface blistering between the teeth. The thin top layer of rubber seems to let go in some areas. Also, there is a definite polished line on the bottom corner where the teeth meet the belt, on the side where the force of the crank pulley teeth is transferred to the belt.

All of this is normal for a new belt, right?
The reason I'm asking is that I have 3 damaged teeth on the cam gear and want to make sure this is not related before I wrap everything up.

Guest765 · 06-06-2011, 03:20 PM

Quote:

Originally Posted by bebbetufs

My new gates belt, (tensioned with the arnnworx tool) has been through one heat cycle. I am running with the covers off to check for issues before installing them permanently. I notice that there is some slight surface blistering between the teeth. The thin top layer of rubber seems to let go in some areas. Also, there is a definite polished line on the bottom corner where the teeth meet the belt, on the side where the force of the crank pulley teeth is transferred to the belt.

All of this is normal for a new belt, right?
The reason I'm asking is that I have 3 damaged teeth on the cam gear and want to make sure this is not related before I wrap everything up.

pics of the belt please

alan6272 · alan6272's Garage

I would say the damaged teeth are not a good thing for the belt. You should fix this first.

Guest765 · 06-06-2011, 04:17 PM

Quote:

Originally Posted by alan6272

I would say the damaged teeth are not a good thing for the belt. You should fix this first.

he had a thread about this. consensus was that he only had a bit of a surface burr on the lip of a few teeth which he sanded smooth.

Grandad#3 · 06-06-2011, 05:14 PM

In the picture shown two of the teeth show sharp edges. These edges should be slightly rounded on the edges so as not to dig into the belt. A flat jewelers file would take care of this problem. There is also a slight crack on the forward edge between the teeth in the middle. I would have replaced the Cam Gear for these reasons, but that is just me.

Cheers,
Larry

bebbetufs · bebbetufs's Garage

I should have said that I've sanded the edges smooth. I have a different cam gear I can use, but I'd rather keep it like it is until I get the turbo outlet pipe from FabSpeed which I'll install after the season. A lot of parts have to come off for that one, so I might as well do it all then.
I'll shoot some photos of the belt on my way to work.

mytrplseven · mytrplseven's Garage

If you have a replacement cam gear and plan to drive this car while you wait for a more opportune time to replace it you're inviting, IMHO, a potential disaster. A timing belt failure because of cam gear damage will really make for an expensive repair. I personally wouldn't chance it.

bebbetufs · bebbetufs's Garage

Thanks for the warning.
I know what happens if the belt fails. Question is if there actually is a problem with this kind of damage. There are no marks on the belt that correspond to the damage on the cam gear, and the blistering I'm seeing ,which really should really be described as flaking, seems to be an extremely thin layer of rubber which is on top of the reinforced belt itself. I don't personally believe the belt is in any kind of danger, but if opinion says to change the gears I will listen.

I did not have the time to photograph it this morning, but I will snap some a little later today.

Thanks.

SolReaver · 06-08-2011, 06:50 AM

It is your Call. Offhand I would say that you are probably ok as long as you don't go too long. IMHO you are better off with a non-buggered pulley. If you still have it off I would suggest a bit of cleaning, deburring, and filling in with cold bond, AKA JB weld or something similar. A little shaping and filling in followed by sanding it down smooth may do the trick. The belt won't know the difference.

bebbetufs · bebbetufs's Garage

Thanks.
The cam gear is on. I've ordered the parts involved in a change, but I still haven't received them.
This is what my belt looks like after running for 15min. max rpm is 3000.
Sorry for the large photos, but this way you can see all the details.

968 GUY · 968 GUY's Garage

Grandad that does look like a crack, but I believe there is a mark on the timing gear to line up w/ mark on cover, or am I mistaken...I know I had to look really hard and turn the engine over to find the puny mark on one of the 968's gear, but I can't remember what the 951's looks like.

SolReaver · 06-08-2011, 01:18 PM

Okey dokey. No prob (at least for me) with the big pics and it does help to see the detail you are concerned with. The gouges in the pulley are degrading the belt from what I can see and your right to be worried. I would suggest a new belt and a new cam gear. If you already have the stuff on order great. Belts are cheap and valves are expensive after all...

I have had some success in filling in belt pulley nicks and such with cold bond. (other makes, but same idea..you would be amazed how often it happens). It does work and you can remove small gaps and gouges. However, IF you already have the pulley in the mail...yea go with that one. Replace the seal while you have the pulley off (duh) and think about the other seals if you are going that far in.

Ya know, I always thought I was being a little over the top when I got all A-retentive with the surfaces thing...looks like my paranoia was just good thinking. Go figure.

And yes...we are getting a little fussy here...but it is all in good fun and for a good cause.

bebbetufs · bebbetufs's Garage

Belt is off, as is the cam gear. Thing is that the marks on the belt don't match up with the marks on the cam gear. If it was the gear that was causing this then the marks should be on one side of the belt, towards the block. Also, I ran another belt on this cam gear for 500km and the belt had no such markings at all when I replaced it because it was walking towards the block.

Any ideas as to what else might be causing this? bad belt?

SolReaver · 06-08-2011, 03:29 PM

Funny that....Weellll... It COULD be some kind of wear from the good surface over compensating, a shift in the materials, who knows? It is a thin belt spinning at several thousand RPM and funny things DO happen. I would chock it off to a bad belt. Don't take it personally, it happens. That is part of the reason that you go back in there to "re-tension". In fact, it is also of an inspection and opportunity to make sure all is well in Denmark. No one will fault you for being over diligent when it comes to timing components on the 2.5.

Continue with the plan. Just think of it all as good practice. I have gone in there so many times I was thinking of having my mail delivered to my engine compartment.

I am assuming everything is put together right and that the belt is tensioned correctly. Just double check everything to be on the safe side. This stuff can be tricky the first few times.

Clean and Inspect the bejessus out of the rest to see if the rest of the surfaces are good. (you prob did that, right?) New belt, new pulley. Put it all together and give it a whirl. Let us know.