924Board.org

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

Since my old post was getting far from the subject, i decided to start a new one. I have noticed a loud whine coming from the front of my engine. It seems to originate from the very front of the head, just below the distributer. Of course, sound can play real tricks on you. It resonates quite well through out the car, and coordiantes with rpms. Just a medium pitch whine.

Naturally I am referring to my 88 924S 140K miles

Lizard · Posted: Fri Sep 16, 2005 2:37 am Post subject:

the timing belt on the 944 2.5L engine will always have a mild hum, even when everything is done correctly, if the hum is too loud it could be that a roller is either failing (NOT good) or that it is too tight, or positioned incorrectly.

do you know when the belt was last done? and what shop did it, or did the PO do it, when was it last tensioned?
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3 928s,

Lizard · Posted: Fri Sep 16, 2005 2:45 am Post subject:

I just read your other post,

so I will go further,
If you do not know when the belt was last done, dont drive the car, and possibly dont even start it. even though the belt may APPEAR to be fine, it could have the fiber strands inside it broken or frayed and could break at any time, or the teeth could fall off. it is NOT worth risking it, take it to a shop and have the following items replaced

ALL front engine seals,
timing belt,
waterpump,
balance shaft belt (belt with teeth on both side),
ALL rollers and idlers.

that should be all, if you dont do all those items then you will have to do them again SOONER, as if you dont do the front end seals they will start to leak and get oil on the belt which will cut its life in half, as well the waterpump will begin to leak and you will have to have it done all over. and if a roller seizes well it will cook the belt faster than you can blink and the belt will break QUICK.
the balance shaft belt could be left off but dont leave the one in there, you will have to replace the seals for the shafts regardless though. and this belt really does smooth the engine out at idle, but it isnt manditory to have on.
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3 928s,

Slam · Posted: Fri Sep 16, 2005 4:12 am Post subject:

Lizard pretty much got it.

But to answer your original question, I'll bet it's your balance shaft belt whining. They're more prone to this than cam belts and can do it even when properly tensioned.

If you don't know when they were changed last, do it now now now.
_________________
'84 944 - kid blew motor
'83 944 - resting comfortably. For 12 years
'87 944 - sideswiped by trucker
'80 924 - gone
'78 924 - gone
'77 924 - rusting comfortably

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

Having taken apart many cars, I will accept that every mechanical part fails at some point if it is subject to wear at all. But replacing everything on the front of a porsche engine seems odd to me. Are the bearings in this car such crap that they can fail at any time when they have some miles on them?
The only car that I have that I can use as a comparison is my MX5. It has very related power, handeling, and size to this 924S. I have redlined this car time and time again, and It now has close to 150K miles on it. I have replaced the timing belt, the water pump, and the oil pump. (For higher pressure only, the original did not wear out or fail.) All bearings and idlers are the same as the day the car was new. And my car drives like a champ!

Just how many Porsch 924S cars have you all observed to actually blow due to idler, seal, or water pump failure? I will readily admit it is possible for any of these to happen at any time, but is this Porsche so delicate? If it is, the fellows at Porsche need to blush.

Gram · Posted: Fri Sep 16, 2005 10:02 am Post subject:

You are only being given cautionary and well-meant advice. Whether you heed it is entirely up to you. Go on, take the risk. You might get away with it

_________________
'82 924 NA Euro (hers)
'98 Audi A4 TDI (ours)

bryanc · Joined: 27 Feb 2003 Posts: 233 Location: San Antonio, Texas

Here is a video of a too tight balance belt.
NO not the avitar! The link at the bottom.
It comes from arnnworx.com
They sell specialty tools for the 2.5 ltr engine.
You might want to have a look at www.arnnworx.com also
http://www.arnnworx.com/MOV00999.MPG
_________________
'84 944
I'd rather have a bottle in front a' me than a frontal lobotomy
Tom Waits

Lizard · Posted: Fri Sep 16, 2005 11:14 am Post subject:

it is VERY common for the waterpump to start leaking if it isnt replaced with the belt, the main reason for this is it tends to get abit more tension from the timing belt over a regular waterpump which is just run off a V belt.

as per the rollers, bearings wear out over time, and on this engine to replace them is CHEAP insurance compared to what could happen.

I am currently doing the timing belt on my 85 Euro 928S and upon diving into that I found that over the 200+k miles the gears have all had the protective coating worn off and I am replacing them as if I dont it will tear up the belt WAY faster, but that is $155 for each cam gear (2), 1 oil pump gear, and a crank gear both the crank and oil pump gear are about $140,
you can do the math and figure out how much I will have into it, (roughly $1k JUST in parts), and I consider that CHEAP insurance compared to what would happen if I dont do it, that would be 16 valves, possibly some pistons, and out of a vehicle for awhile.

If you are VERY mechanically inclined then you can replace the parts on your own and then either buy the tool to tension or take it to a shop to have them tension it for you. but use a tool to tension it.
When I do 944 TB I actually set it by sound, and tell them to make sure that around 1000km that they take it to a shop and have it retensioned at a shop, or to have it tensioned right away with a tool,
I make sure that the 944 owner KNOWS and AGREES that I am not held liable for any damage caused by the belt breaking and they know what I am doing.

good luck with it, but please dont ignore the warnings.
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3 928s,

Paul · Posted: Fri Sep 16, 2005 11:55 am Post subject:

Head on over to 944 forum on Rennlist and search on "bent valve" or "timing belt"

I think they average at least one broken belt a month, probably more.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

timstar92404 · Joined: 22 Sep 2004 Posts: 2075 Location: richmond BC

is an engine with a timing "chain" safer than a timing belt?

I think timing chains are replaced at 100k miles or kms.

Also I've heard alot of different things about the 944 timing belt. Alot of people here say it needs to be changed every 30k miles but i've heard every 60k miles from alot of sites on 944 maintenance.

also don't the 87+ cars have automatic tensioners? would this make the belt a little safer?
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78 924 sold.
85.5 944

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

timstar92404 · Joined: 22 Sep 2004 Posts: 2075 Location: richmond BC

I wouldn't mind more noise if its more reliable.

it would be nice if they made and unripable / unstretchable timing belt that cost more than a regular belt but never needed replacing other than tensioning..... I'm sure its possilbe.
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78 924 sold.
85.5 944

Lizard · Posted: Sat Sep 17, 2005 12:50 am Post subject:

timing chains do stretch as well, and when they stretch they tend to break teeth off the gears and then they can get lodged and do alot of damage, however that being said it is less likely for it to happen than a timing belt failure.

as per the timing belt intravels, the 2.5-3.0L engine is 30k MILES, (you could get away with abit more if a 8V, but I STRONGLY recommend against it)
the 928 for all engines were listed to be 60k MILES which is just under 100k KM, however most places recommend to change it at around 45-55k miles.

so that is where you were getting the 60k miles Tim.
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3 928s,

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

If the balance shaft belt is a liability to have in the car, and removing it allows the car to still run, then it is a very tempting idea. I would have to be told, (and believe) that this will not adversely affect the car. I dont care about rough idle, but will exclusion of the balance shaft belt make the car run rough at high speeds, possibly causing accellerated wear?

I cant seem to get my hands on idlers for this car, so I guess I will examine the existing ones very carefully, for smooth operation. My only solution to the leaking seal problem is to pop off the timing belt cover every oil change and have a peek. Its not really hard to do.

I have acquired a Haynes manual and have decided that the hum I hear centers around the water pump pulley! Dunno. You could get tired of this car really fast I think.