opinion on TB/WP etc R@R

psychII · 07-06-2007, 01:26 PM

I am in need of some answers and opinions regarding TB/WP replacement.

My new to me (2 months) 86.5 came with a receipt dating 2004 for a timing belt/water pump replacement. While browsing the engine bay today, I pulled off the air intake tubes and peeped into the TB vent. It appears that the belt has migrated to the very edge of the cam. While still being new to the 928, I know enough to feel that this is not good and I do not plan to drive until corrected.

My question is, when I tear into it this weekend, what in particular should I be looking for that would cause the belt to migrate? Worn bushing, bent bolt?

As far as opinions, can I get by with replacing the belt and what ever is worn/broken, or do I need to do the complete system? I ask because I am going on vacation next week and 928 funds are limited and the water pump is still fairly new. I don't mind having to go back in sooner than later in the likelihood it seizes or develops a leak.

Thanks in advance for your suggestions.

Chris

Danglerb · 07-06-2007, 02:03 PM

When you go in, you should bring everything up to your standards, if the TB has to come off EVERYTHING related should be like new when it goes back together. Its not good to assume the previous owner or their mechanic did anything remotely well or correctly.

I've read a couple TB stories with same sounding problem, with I think two sources, bent tension bolt, or a missing or bad bushing.

The belt IIRC doesn't just move forward and stop for no reason, its rubbing on some bracket and slowly being eaten up.

There is a good write up on a couple sites, plus many find the guide with pictures that sold on ebay for $15 to be money well spent.

psychII · 07-06-2007, 04:47 PM

Thank you for the reply. I do question the previous mechanic. Looking at the reciept, I can't tell what was done other than the basics, but at $2300.

There are generally two schools of thought, repair while there or if it ain't broke, don't fix it.

I am considering the second. From what I have read, it is either a bushing and/or bent bolt, causing the migration. Once to a certain point forward, rubs against the tensioner arm.

I have the manuals and ebay book and going to go in and see what it needs. I'm not in a position at this point to replace things that don't need replacing. I think I'm going to assess what is needed and fix it, and then do the whole deal at the next interval.

Thanks again. I miss driving my car!!

SeanR · 07-06-2007, 06:18 PM

First post here. Sorry for no introduction. Long time lurker, never poster.

The best thing to do would be the replacement of everything, from the cam gears to the tensioner rollers. There can be an issue with the a bolt on a tensioner roller that causes the belt to migrate to the front of the cam gears, it could also mean the belt was put on backwards (heard this, never seen it).

If you do the entire W/P, T/B, tensioner rebuild yourself, you will only spend about $600.00 +/-. The plus or minus being what else you decide to take care of while you are in there. Such being, hoses, temp stat and other pieces that need to be replaced.

Good luck on it and don't skimp. You just might be sorry if you do, in the long run. There are many great write ups on the net on how to do this and a decent one on e-bay for about $15.00.

Bob

Danglerb · 07-06-2007, 08:45 PM

Really the only "optional" part I can think of is the water pump. Everything else is either routinely replaced, or possible to fully inspect and only replaced as needed.

SeanR · 07-06-2007, 09:26 PM

Mike, if you were to fully inspect, what would you be looking for? If you pull the w/p off, surely it is the best thing to just replace it. It's only $100.00 after core charge. Granted the gasket is only a few dollars but there is really no real way to tell if your pump is going to go in 500 miles or 50,000 miles.

Danglerb · 07-07-2007, 12:39 AM

Water pump view some have is, no leaks, no squeaks, then don't touch it, or only replace every other timing belt service. If it comes off a rebuilt should be going back on, otherwise maybe best to avoid touching the often breaking water pump bolts.

Thats the deal with the TB/WP service, its half a dozen jobs all sharing a timing belt; water pump, tensioner rebuild, cam gears, bolts and pulleys, etc. All are critical, individually they are also cheap, so none of them should be skipped if the timing belt is coming off anyway.