cam tensioner questions

odie · 07-09-2003, 12:29 PM

Is the tension maintained by oil pressure or spring pressure?

If the chain stretches will there be a problem with valve clearance on the camshaft thats driven by the chain. Or does the cam start to lag behind and increase valve clearance?

If the plastic ramp is worn out or wearing out what kind on noises might you hear?

My 87 944S starts up and idles fine with good oil pressure. But as soon as I raise the RPMs a little I start hearing distinct and loud knocking/tapping sounds from under the valve cover. It sounds very high up in the engine and more towards the middle of the head.

I originally thought that this was the sounds of the valves starting to "kiss" the piston but now think it could be maybe the chain and or tensioner making the noise.

Shifter · 07-09-2003, 12:40 PM

When I looked at mine, it appeared to be a combination of a spring and oil pressure. I think the spring maintains the tension when the engine isn't running, and the oil pressure pumps it up to keep the chain tight when it is running.
The pad was good on mine, and it didn't make noise, but if you are have some noise, I would take the cover off and give it a visual check at the least. Only takes a few minutes to take it off, and the gasket set is only 30 bucks or so.

Your call, but it is cheaper the replace the parts, than a head...

T

carsontc · 07-09-2003, 02:28 PM

this is the 3rd time I've said this in about 3 days...dunno what is is with these 16v P-cars this week but..

"if I owned an S with a rattle noise from the engine I would turn it off and tow it to a Porsche machanic to have ALL the usual parts replaced plus the front seals" and maybe even a water pump and rod bearings if the car had over a 100k on it

every couple of weeks someone starts a thread about either a belt roller locking up or a $25 tensioner pad breaking or a waterpump siezing or one of the belts loosing a few teeth or a belt quietly breaking...

whatever the "usual" part that fails is, it almost always ends up costing a few grand (or more) to fix...or they 'part-out' the car

do you have receipts for the maintenance done, what parts changed and when?

odie · 07-09-2003, 06:45 PM

I bought this car in this condition (cheap) and am planning on a total engine rebuild. It will still be a couple of months before I can pull the motor so its just sitting (I've never driven it). I'm just looking for some possibilities of what the problem may be so I know what to scrutinize when I rip it apart.

The seller ran it low on oil and the next day it made all kind of bad noises. He was told "rod bearings" an decided to sell it. Turns out the oill just got low and the pump lost it's prime going around a corner. The next day the lifters bleed down and collapsed and was causing the racket. I reprimed the pump and the lifters seem fine. But now I can hear a distinct knocking wich I believe to be related to the tensioner and hopefully not valves.

carsontc · 07-09-2003, 07:27 PM

Quote:

Originally posted by odie
But now I can hear a distinct knocking

my experience with a distinct knocking sound is it usually was something very bad in the lower end

plan a total rebuild...don’t skimp on any part that is a lot of labor to install...pull the engine and do it once by doing it right

or just part it out

odie · 07-10-2003, 10:10 AM

I'm pretty sure the knock is in the top end. It appears to be right under the center of the valve cover...that's why I'm thinking tensioner problems.

SoCal Driver · SoCal Driver's Garage

Low oil = seized rod bearing = loud knocking.

Colapsed lifter = clatter not knocking.

Figure complete rebuild.

odie · 07-10-2003, 02:07 PM

it had lots of clatter. but as soon as I primed the oil pump it went away fast.

I'm not sure its a rod bearing. It just doesn't sound deep down. When I rebuild it everything is going to be replaced anyway.

I just need to pay extra attention to the source of the noise on my rebuild as thats probably were all the wear will likely be.