Engine noise

911buff · 911buff's Garage

I am new to the 924/944 engine and have a 1987 924S... so how much "whine" is normal? I am thinking that the lower pulley of the timing belt is possibly going bad but again, I do not know the engine noises. Is a whine normal?

John_AZ · 07-03-2016, 08:25 PM

You need to take off the belt covers.

On a cold engine........
Set the engine to TDC
Usually the whine is the balance belt.

balance shaft whine noise

Check the tension on the cam belt by grabbing the water pump pulley.

On a cold engine.......if you can turn the WP pulley with one hand and it feels loose-----it is too loose.

If you can turn the pulley with one hand and it feels just snug----it should be OK

If you cannot turn the WP pulley with 1 strong hand or 2 weak hands it is too tight.---It will whine.

Retension both belts with the correct method or guage.

As the above thread states----the balance belt should feel sloppy.

Check the WP by grabbing the pully. Tug sideways----tug in and out---tug up and down. There should be NO play in the pully.

Spin the rollers. If they feel like roller skate wheels---replace.

J_AZ

Arizona_928 · 07-04-2016, 02:19 AM

If you over tighten the bs belt it'll whine like a blower

v2rocket_aka944 · 07-04-2016, 07:05 AM

John AZ..

Over the years I've done timing belts on probably 30-40 cars.
I go by the twist method, even for the spring tensioner engines.

Maybe my fingers are calibrated differently but when I set the belt as "90 degree tight", never been able to budge the pump pulley.

The whine is always caused by people over tensioning the balance belt because they can't believe a drive belt should be as loose as that one should be.

dgcantrell · dgcantrell's Garage

Yeah.. The first time I ever did mine, I got it too tight and it whined.. The 90degree twist is good measure to go by but there's a German fellow on Youtube (he posts here, Jurgen is his name, I think) that says 130 (or there abouts) is what he sets them at. I'm somewhere in the middle at just over 90 to 120 and have never had a problem since.

I broke down and took it down to the dealer the first time I did it back in 1993. The mechanic there showed me how to set it. He was pretty cool about it knowing I was a young Porsche wrencher and that I would probably never be able to afford using the dealership's services anyway. I'm 48 now and still can't.. LOL

John_AZ · 07-04-2016, 07:37 AM

Hi v2,

The new belts are installed on a cold engine. The engine when at operating conditions will expand ---maybe 6 to 8 thousands----adding more pressure on the belt.

On a new belt, your method is probably accurate as the belt will stretch, set in the gear teeth and rollers and I am almost certain if inspected at the retension period of ~about 1000 to 1500 miles the belt against the pully if checked, could be "budged" or rotated with 1 strong hand or a pair of weak hands.

The water pumps on my cars were installed in 1996 ('88) and 1998 ('87). I believe the belt tension method I use will extend the life of the WP bearing.

My "belt tension check" is 150 miles after I install a new belt. Just to make sure the belt teeth have "set" into the rollers and gears. After that yearly. Members that have a leaking front crank seal, or another front seal should check the belts every 6 months.

You have the skill and years of getting the correct "feel" on the 90' twist method.

My WP pully test is a second option.

Enjoy the 4th!

John

v2rocket_aka944 · 07-04-2016, 09:51 AM

I'm putting an engine together, a real Frankenstein, and it's getting the 968 automatic setup so my life will be easier...

911buff · 911buff's Garage

Thank you for the advice. The engine was rebuilt just before we bought it, so there is a good chance that the balance belt is too tight. Will check the tension and report back. Thanks!