DZGunner

So this morning (it was a cold one) I started my 928 and let it idle for a bit while i moved stuff and get ready to head out for school. I got in my car after it ran for about 3 minutes and decided to rev the engine a bit, because why not. well at around 4500 rpm i heard a pop from the exhaust, it was just one. I thought nothing of it and started driving to school, I literally just pull out of the corner onto the main road and my belt tension light comes on. so i hobbled my way to school and brought it into the bay (i'm an auto tech student and planned on checking it out at school). After about 4 hours of classes i was finally able to come back to my car and attempt to start it, it cranked and sounded like it wanted to start, but wouldn't. I've had this happen before without any belt tension lights or issues and was able to start it after 4 tries or so. But the prof recommended i stop and we'd just push it to a lift.

Any suggestions as to what may be the outcome? I was able to drive it to school just fine, other than that one pop from revving i heard no abnormal sounds. also, does the belt need to be manually tensioned occasianally or is it always tensioned with the hyrdualics in the tensioner. I'm in the process of getting the timing cover off so i'll be able to post anything i find. I'm just wondering if this happens alot, or if i may have engine damage or what.

The Fixer

Hey Ryan,

I hope you do not have any engine damage and have a feeling you will not.

Take a lot of pics please, i am sure many are curious.

On a side note; I won't drive my car in this cold.
(I just can't stand the idea of the motor being 8 degrees F and then over 180F and back down again.)

I know it's designed for these extremes but i always consider the car and it makes me cringe.

I know your 28 is a DD though, and you don't have the option right now.

Anyway, i really just wanted to say hello and wish you luck.

Sounds like great fun to be in school for this.

James Bailey

reving a cold engine especially to 4,500 is abuse....great way to blow up an oil filter and real hard on everything else. Hard to say why you are having problems. It takes 15 minutes or more for your oil to warm up.

The tensioner is not oil pressure fed nor does it self adjust. A new belt needs checked and tensioned after a 1,000 miles or so but SHOULD be OK for many thousands of miles after that.

DZGunner

Thanks guys, Ok i was under the impression that the tensioner was doing it's own thing and i didn't have to manually tension it, I also had no idea you have to manually tension it that often, i got the car with 163k miles on it, and here i am at 175k... so i'd say its been a while. either way, at this point i'm going to replace the belt to be sure its good and new. Can someone refer me to a good belt tensioning write-up please. Also is it possible to tension the belt without the special tool? the school has a tensioning tool but it doesn't have a dial indicator on it or anything, just a couple notches for reference (keep the line between the notches and its good essentially.

You won't hear me revving a cold engine anymore, hopefully not because i can't, but because i've learned my lesson.

DZGunner

its an 87 s4 by the way, which is why im so worried, with the interference valves.

James Bailey

The simple tool is a probably a reproduction Kempf tool which for the S-4 you want it to the tighter notch. There are several very good writups about doing it. You will also want to change some other parts as the write-ups will point out.

DZGunner

thanks james

awilli6

Use Dewaynes write-up. Its complete with pictures and everything. My TB had been changed 5 years earlier when I got my car and it had only gone about 1000 miles. I got a tension light and decided to change it. The belt was fine but the tensioner was literally falling apart (I'm very lucky). I would change everything. Get the porkensioner if you can.

DZGunner

I was just looking into that, i'm waiting on a price check from roger

jcorenman

Gunner, do you know the history of the car? You've had it for 12K, but do you know when the belt (and water pump) was last changed? (And at what mileage?)

The backfire, and the hard starting, suggests that the cam timing might have shifted-- i.e. the belt possibly skipped a tooth or two, because it was loose, or cold and stiff, or maybe just old and cracked.
If you haven't looked, you don't know anything. (I don't mean that unkindly, but decisions need to be based on information, not guesses).

A good place to start is to pull both belt covers, rotate the engine (clockwise, facing the engine) to #1 TDC and check the timing marks on the cam. That will tell you whether the belt has slipped.

Also have a good look at the belt, and how it is tracking on the cam sprockets, and ave a look at the sprockets and see what kind of shape they are in. Post some pic's, get some opinions, and then you can decide the best course of action. It may be something simple.

Alan

But what Jim didn't say above is that unless you know how old the belt is with some documentary proof - you just have to assume it has passed its sell by date and replace it - else you are risking very expensive engine damage. If you can do all that in the shop at school it needn't be too expensive...

Replacing many damaged valves would be much more expensive indeed...

You will need to retension soon after a belt change.. plan for it...

Alan

s4hounddog

Once you get the inspections covers off the motor, do a visual then simply pull, prod and poke the belt with your fingers. If it looks ok, get the kempf tool and check the tension, slowly rotate the motor ( with a socket on the harmonic balalncer bolt) and check the tension again. Re-tension to kempf specifications. If there is any doubt of the condition of the belt replace it!
The following is an earlier link with good step-by-step procedures on checking t-belt tension.
http://members.rennlist.com/v1uhoh/checking.htm

Gary Knox

If your belt tensioner hasn't been rebuilt recently (last 2 belt changes), it should be rebuilt. Roger can give you the details and price for the parts needed to rebuild it.

Alternatively, many of us have 'invested' a few more $ and installed the Porkensioner from Roger. With this installed, a new belt does not need to be re-tensioned after the 1K to 1.5K miles. And re-tensioning should not be needed during the lifetime of the belt you are installing.

I agree - it is NOT good to rev a 'cool' engine. My understanding is it takes about 3-4X the length of time for the oil to reach full temperature as it takes for the coolant to get there.

Gary--

Alan

Lets remember that unless you know for sure how old and how many miles are on the current belt there is ALWAYS doubt - regardless if the belt still actually looks good and has good tension...

Visual inspection and a tension check result will tell you if the belt is on its last legs, but it can't really ever tell you that it is good for another x?K miles. It does give a pretty definite idea of the cam sprocket wear though.

If it were me I'd want to know for sure when the belt was last changed... and at this point there may be only one way to know that.

Alan

davek9

Wanted to add this: the T Belt tension needs to be set on a "cold" engine, not hot or warm when using the stock tensioner, as you want it to be fully retracted.

Dave