Timing Belt Wear Question

[SkudR33]

Hey guys,

Abit of background information - I have an rb2530 that's only done about 2500kms. Due to bonnet clearance I'm no longer able to install the timing covers...

Today I was completing a quick lookover though the engine bay and noticed the some rubber marks which have been transferred off my timing belt onto the pulleys... I had a look about 4 weeks ago and these marks weren't existent - since then I've driven the car maybe 2-3 times.

Just looking to get some opinions as to why this may be happening and whether or not anybody else has experienced anything similar!

[iruvyouskyrine]

No idea about the marks, but the first thing I notice is how far back your timing belt is sitting on your cam pulleys. All RB's I have ever see it should be sitting centres or maybe just slightly forward. Yours looks fully back.

No idea if it should make a difference to anything, just something I noticed.

[AngryRB]

Does yours run 2 tensioners or 1 tensioner and 1 idle pulley cause in the guide it mentions that using an idle pulley increases the belt tension above normal.. just a thought

[89CAL]

Without the covers on, I'm thinking maybe something got in there and got caught between the belt and pulley or something along those lines breifly

It looks like it has rubbed on something anyway

[mr skidz]

Looks like the bearing has seized and Belt is rubbing against the surface causing some hot spots,

I'd get that bearing looked at ASAP

Edited September 27, 2015 by mr skidz

[Hadouken]

Agreed. And push that belt forward. Looks like it might be touching the on the rear part

[nick81xd]

Was the rear shim put back in behind the crank pulley when belt was installed??. that would cause the belt to naturally run on rear of pulleys

[SkudR33]

Pardon my delay in response guys - had no idea anybody replied to my post...

I'm running two tensioner bearings... What I also noticed is both of the bearings have identical rubber transfer marks on them. I think that kinda rules out bearing seizure unless they both seizing at the same time.

In terms of the belt sitting towards the rear - I got no idea why it's like that but I've definitely reinstalled the rear shim when I installed the belt...

Also turned the car on and had a close look, it seems as though the belt is loose. Either the belt has stretched or one of the tensioners have loosened up.... Would that cause that severe rubber wear though????

I appreciate the replies guys... Love the feedback this club has given me for the last few years - I'll definitely keep you guys filled in if I make anymore interesting discoveries!

[mr skidz]

Don't thrash it, had the same thing on my first R32 it was a combo of noisy dry bearing and a loose belt, but not loose enough to beat 2 cars in a race driving to the repairer. Lol

End result was advan performance when they were in silverwater removing my timing cover (rookie error) and revving my car even though we'd already established the issue being the dry bearing.

So I got a phone call saying

"something doesn't sound right with your head, it seems to have bent a valve or valves"

Let's just say from that day on I learnt to do everything on my car myself.

Trust nobody unless there considered a friend.

People are shit sometimes and they will have brainfarts that sometimes cost you unnecessary money.

Sorry for the rant but this issue your having and a few others made me how I am today.

Get it looked at ASAP,

Good luck

Edited September 29, 2015 by mr skidz

[jiffo]

The spot where you mounted the idler, was that on a factory machined area?

[SkudR33]

The spot where you mounted the idler, was that on a factory machined area?

Yep [emoji20]

[Ben C34]

Shouldn't there be a belt guide on the back of the crank pulley?

[Ben C34]

I'm spazzing. Do t mind me.

[Fry_33]

Make sure something hasn't dropped down into the bottom cover. It could be something sitting in between the cover and the back of the belt.

It looks like you have the rear flange on the crank pulley, it has a smaller OD than the front one.

The belt will sit where it wants on the pulley face. The pulleys should all be aligned as long as the added idler is correctly done. The flanges on the crank pulley will prevent it from tracking off the edge of the other ones.

Edited September 29, 2015 by Fry_33

[SkudR33]

Haha Ben I thought the same thing when I first uploaded the photos... I took the covers off, all was clear - one thing I did notice though is the belt was slightly under tensioned... This was causing it to walk towards the rear of the gears.

Good news - The black marks are slowly disappearing now after I retensioned the belt however I believe the belt is coated in this tacky rubber material so I'm going to replace it.

One further question, the belt still walks a tiny bit however it now sits in the middle to front region of the cam gears. I can't remember if it used to do that on the rb25... How much walk is considered safe?

[Missileman]

I've never seen one that sits perfectly in the middle.

[iruvyouskyrine]

All mine have sat very close to the middle, or just slightly forward +/-2mm

[SkudR33]

All mine have sat very close to the middle, or just slightly forward +/-2mm

That's where it's sitting now I reckon - hoping it all goes well from here... Kinda shitting my pants because we all know timing belt problems can ruin a mans day! Lol

Thanks for the help guys - I'll definitely keep everybody posted as to how it all goes from here...

[Fry_33]

Glad to hear it's looking ok now.

Timing belts track due to the way they are made.. the tensile cords inside the belt that give them their strength are twisted glass fibres, when put under tension they want to unwind. This causes a slight tracking force to one side. If you flipped the belt around the other way then it would track in the opposite direction. That's the whole reason for the flanges. If you have any angular misalignment of sprockets then it will force the belt to track harder to one side. For standard setups this is not really an issue as everything is machined and in line. As always, once you start modifying things, that's when you need to be cautious of the tracking. As long as everything is line, tension it up and let the belt do what it wants

A mark on the back of the belt normally indicates that something stationary has been in contact with it. That will obviously cause heat and can lead to transfer of heat and possibly rubber to other components like the idlers. That's the main reason for me asking about anything dropping down into the cover.