Porsche 944 timing belt system 2

[RossABQ]

I've recently purchased one of these cars, an '84 normally aspirated model. These engines are famous for eating their valves when the belt breaks/slips/feels like it. Searching on-line I've found instances where qualified techs installed a new belt and idlers (all the bearings and belts are sold as a kit) and the engine ate the valves as little as 9,000 miles later, at idle, in the owner's driveway. It happens so often that the most common mod to these cars is to install a Chevy V8.

Do any of you in the industry have any insight as to the problems with this system? I see nothing unusual about the system, if anything it seems to have lots of wrap on the pulleys and good support along its runs.

Porsche subsequently went to chain drives on the turbo models of this engine, and they seem to have their own set of problems.

 

[raceu]

I have built 944 motors and raced 944's for the past 6 years and have owned 944's for 15 years. The timing belt system in the 944 is a well designed including the updated system which is only as good as the person installing updated/new parts and belts. Several problems occur when installing a new timing belt, balance shaft belt, rollers and other parts. The reason for the guide was due to the larger pulley on the Turbo style water pump which was updated due to the additional heat generated by the turbo having water pumped through it to keep the turbo cool. The larger pulley required a guide due to the lack of clearance as the belt passes closer to the other half of the belt which also required the change in the roller size. When the timing belt is reinstalled many times the belt is installed off by one or two teeth a common human error and or due to worn keyways and or the head being milled on a rebuild or cut 40-60 thousands for increased compression. The entire pulley system can be off by one tooth and the only way to verify is with a cam degree system such as Web Cam check. Another problem is the failure to have the belt adjusted after 500-1000 miles as required by Porsche. Another failure is not the belt but a roller due to a failure to replace or inspecting and upon inspecting incorrectly believing a loose spinning roller is good when in fact is worn out as the rollers should show resistance when spun. Finally the installation of the balance shaft belt incorrectly causing excessive vibration and wear including the failure of the fuel rail do to the continued vibration with an end result of an occasional fire, exhaust cracks, loose nuts and bolts. The balance shaft system was designed to keep the motor running smoothly at idle and lower rpm. I remove the balance shaft belt and all rollers in both my race cars and street cars. I have changed belts in a 22 year old turbo based in dry Arizona with the original belts and water pump with the small water pump pulley. The belts were so worn I was able to peal off the ribs. I change belts every 2-3 years depending on use as a cheap investment to valve train damage at a cost of $20 for a timing belt there is no reason for a broken belt done properly and changed every few years. One last failure I have seen was due to over tightening a pulley and the stud broke off causing the timing belt to be destroyed, human error with an air wrench! Too many people wait until 30,000 miles which can be 10-20 years. Anyone with a Hanes or equal manual can perform all of the belt, rollers, water pump work and keep these well engineered cars running smoothly. All of the above information I have provided is from my experience with these cars. I have yet to see a timing belt failure under racing conditions.

 

[evelrod]

raceu speaks to a problem I've seen many times over the years..."I just don't know what happened, I followed the instructions to the letter, but it just won't run right"!
Pretty good 1st post in the forum, I'd say.

It was never ok, in my shop, to change a belt or chain without taking the time to double ck the timing...An easy step that should always be done. Many engines that have separate drives for balance shafts, dist drives, oil pump drives can very easily get 'out of sinc' and cause monster problems, even if the camshaft timing is correct.

I have made no secret of my disdain for 'belt drives' in the past and nothing has happened in the last few years to change my mind. I used belts on the cam drives of a couple Ford/Cosworth based race engines that worked well enough---with constant maintenance! For a street car, it's a shortcut in mfgring that I could do without...I won't buy a car with a belt.

Rod

 

[RossABQ]

raceu, You've brought up a pertinent point; Porsche recommends that after you pay a mechanic maybe 4 -6 hours labor to put the belts in (simplest scenario, even more for a water pump job), you are supposed to drive it a couple of weeks and then pay him to essentially re-do the job, "just to be sure"?! Name another car where this is called for...

I did my belts and the water pump upgrade, and haven't had any problems so far. Well, just the normal Bosch problems...

 

[PackardV8]

Hi, Ross,

You said, "Porsche recommends that after you pay a mechanic maybe 4 -6 hours labor to put the belts in (simplest scenario, even more for a water pump job), you are supposed to drive it a couple of weeks and then pay him to essentially re-do the job, "just to be sure"?! Name another car where this is called for..."

As always, your car, your money your decision. However, raceu gives it straight and true. I've known 944s and their owners since the car was new. Some are made for each other; some are not. My suggestion, based upon many years of observation - Cut your losses, sell the 944 now. I can opine from your posts you are most likely never going to be happy with the car.

thnx, jack vines

 

[RossABQ]

Jack, you have hit the nail on the head! I am full of angst over what could go wrong on the car. I've been driving it and like it in many respects, but the thought of having to replace the torque tube bearings (around $2500 at the shops, and some parts are no longer available) or similar work is ever-present in my mind. I'm becoming comfortable with the cam belt system. Of course, the TT bearings are noisy... So I don't know what I'll do. I have $2500 into the car, it gets in the mid-20's for gas mileage, and is a nice looking car. I could throw a lot of money into it, and still have less into it than a crappy Hyundai that needs no maintenance but is thoroughly boring. Not like I'll be in the bread lines if it nukes out.

 

[evelrod]

Ross, Jack is right on. Eliminate all the stress and just sell the damn thing! There are several very nice, maintenance friendly sporty drives out there, perhaps a Miata, a MR-2 or something like that would better suit you. I have a couple of friends that owned the "hatch back Audi" and were never happier when they sold them. Obviously they are, like my Lotus and Mini Cooper, NOT for everyone!!!

No worse feeling than the realization that you have just thrown good money down the drain...unless it's the knowledge that you are STILL doing it!

Rod

 

[RossABQ]

We'll see, I need something to do in my retirement (was going to be in 3 yrs -- now, who knows??)

 

[evelrod]

Retirement will always be "just out of reach". At least it was for me, for years...I finally just 'bit the bullet' and pulled the pin (don't you just love the English language?) in 1998...It cost me a bit, retiring early...I'll never regret it, best thing I ever did. I got lucky with the stock thing and cashed everything in in Nov. of 2007, Whew! However, I have cut back on some of my automobile hobby stuff, sold my '37 Buick and my '58 Morris and, on that same note, I have my '59 Nash Metropolitan up for sale (such a deal I can make you, Ross!!!)...I'm cutting back because I'll be 69 next month and I just don't have the energy (desire?) to mess with all of them.

Hope you make it ok. Seems like a lot of members are loosing their jobs...That sucks, I know...BTDT!

Rod

 

[Lou Scannon]

rod, I'm filled with encouragement at the thought that if I can follow your example, I have 20+ years to go before losing "the energy (desire) to mess with all" my toys, present and future.

 

[evelrod]

Hemi, you will be pleased to know that I have not given up completely...Just sent in my entries for a couple upcoming events for my Mini Cooper race car. This year is the 50th anniversary of the Mini...

http://www.canam50minirace.com/Entrylist.html

http://forum.moasf.com/index.php?topic=2875.0

If your in the neighborhood...Also we are taking the Lotus Cortina out to Willow Springs in April 4th/5th VARA race for my son to drive his first race.

http://www.vararacing.com/

Rod

 

[thedge]

Hehe most common mod is a Chevy V8, thats pretty good.

When the belts are replaced on a 944, it must have the tension checked 1500 miles later. The new belts stretch out a lot. Its a quick simple procedure, I think shop time is specced at 1 hour if that for an 944NA. The plastic belt covers are removed and the tension should be checked with the tools designed for the job.... Not the hokey finger twist method. If it doesnt get checked on schedule then the belt gets too loose and damage can happen. No reason to sell it, as long as you follow the proper maintenance schedules and procedures for doing the belts.

 

[RossABQ]

Just a shame that the "tool designed for the job" costs upwards of $500! I pulled off the one plastic cover, the belts have maybe 200 miles on them, and the tensions seem to be the same as installed. No noise from the balance shaft belt, always a good sign.

 

[PackardV8]

“The fault, dear Brutus, lies not in our stars (or in the 944) but in ourselves.”

My point was the OP has a unresolvable conflict between what is now a very cheap car to buy, but a very expensive car to maintain. My experience is OP will let the maintenance costs obscure the unique virtues of the 944 and resent more than enjoy the ride. As Willy Nelson titled one of his earlier songs, "She's Not For You."

thnx, jack vines

 

[RossABQ]

There's an interesting thread on the Rennslist forum; "What is the true cost of those $1500 944's?"

http://forums.rennlist.com/rennforu...what-is-the-true-cost-of-those-1500-944s.html

No surprises there...

Jack, my original post was questioning how Porsche, a preeminent engineering house, botched what is a basic system mastered by every 3rd tier auto manufacturer. It has kind of devolved into a rant or whining session, my apologies for that. I actually find the costs of parts to be more or less stuck in the '80's, a 5-yr-old Camry would cost more to repair, part-for-part.

 

[patprimmer]

The cost of parts is irrelevant if you never or rarely need them as is the case with the Camry, but not the Porsche I expect.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Lou Scannon]

rod, thanks for the inspiration... keep the faith!

 

[thruthefence]

Rod, did you, as I, in the fall of 2007, look around at the proliferation of furniture/home electronics rental stores, pay check loan establishments, check "cashing" outlets, and say to yourself "what is happening here?" When asked, My money guy told me that the revenue stream from these businesses, ( all owned by big firms, Citi, etc) was "packaged" and sold into the derivatives market, like a bushel of wheat. Ya know, you can at least eat a bushel of wheat. You can't eat a "promise to pay" from consumers who cannot even live paycheck to paycheck, without kiteing checks ( for a 'fee', of course ). At that point I went to 80% cash, tho I am 6-7 years out from retirement. Glad I did.

 

[evelrod]

I lost my shirt in the 2000 tech "market correction"...Enough so that I went back to school and took courses in commodities trading. I did that for a few years, not too bad...a little better than 'even', mostly gold and silver. I gave that up as it was just too much work. It did, however, teach me the lesson of "DON'T GET GREEDY". In '07 things just started sounding too good to be true. I'd been through one correction in the market and it was looking much the same. I bailed out, perhaps a little early to catch the peak, but that's just fine with me (in hindsight)!!!

Hang in there, I did not start preparing for retirement until I was 50. I planned to retire at 65, but things worked out so well that I retired at 58...Best thing I ever did.

I've kept up with my old portfolio...if I had stayed in the market, I would have lost >60% !!!!!!!!!!! I'd probably be one of those "greeters", the old geezers, at Wall*Mart ;o(

Rod

 

[thruthefence]

Great story, good luck with the Mini & Cortina.