How hard is replacing the 16V timing belt??
 

I have a 944 that i would never attempt to replace the belt, but after looking at the 928, I'm almost tempted to make a run at it.

I've not found a really good procedure for doing it (the shop manual almost looks like it' missing a page, only talks about putting on a new one) so if anyone has a link to a good step-by-step procedure I would appreciate it

Has anyone done it? I'm of "average" ability i guess, never done anything quite like this, but do have the advantage of time..this car is in "restoration" phase, so it can sit for a while if i get flustered.

Part of me just says to take it into the shop (I am fortunate to have a good place nearby that can work on 928's), but it seems like it would be a good learning experience.

on the 944, 1 mistake= dead engine, so I decided when i bought it I wouldn't try it.

Any advice guys?

it's a 7 on a 1-10 difficulty scale, you will need some special tools to do this
flywheel lock, and the Kempf tension tool
there are a couple writeups on the procedure on the internet, you may want to try to hook up with some other 928 owners in your area and have a tb/wp party

US 16v is non interference, but the Euro S isn't non interference, so timing errors bend valves.

TB/WP party is what I would suggest, nothing like somebody around thats already done it, plus a few beers can lower your anxiety. ;)

I wouldn't suggest it as a weekend project if you need to drive the car to work on Monday, because issues may come up that are best solved slowly or may require delays for parts shipped. Best results seem to come from ordering EVERYTHING you might need from somebody smart enough to put together a parts kit for you.

I wish this guy on ebay would do a 16v guide, nothing but rave reviews for the detailed manual he has done for the 32v cars. He comments that the early 16v are simpler and that his guide can be used just skipping the 32v sections, but I haven't heard much about using it on a 16v.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=190142443387

Here is a link to great tips and links, and great TB links specifically;
http://www.nichols.nu/tip686.htm

An excellent, detailed, step-by-step procedure for replacing the timing belt on an '87S4 can be found on John Pritle's web site at
http://members.rennlist.com/pirtle/tbelt.html

John Krawczyk's web site shows how to do a t-belt change on a 16-valve engine:
http://members.rennlist.com/blueshark/page14.html

If you fail, what have you lost ?

I "assisted" Donnie at Zotz garage in Orlando, Florida at my last timing belt change. Donnie has done dozens of 944's and 928's, and knows ALL the ins and outs and all the little detail points that that revolve around this job.

Over on Rennlist, there is a guy named "BigDave", and the name is appropriate.
Well, he needed to change out the belt on his '85 32 valve. He bought parts from reputable suppliers and employed several amatuer friends in his weekend endeavor. Unfortunately, none of them noticed that the pin that forms the pivot point of the belt tensioner was NOT screwed into the block far enough, and it bent. This allowed the tensioner to move to a different position, and the belt allowed the valves to hit the pistons.

A Porsche piston is expensive. But one at Champion Porsche? Unless it is a 928 then it is an ugly deal.

Even an '81 looks intimidating at first glance (85-86 are very intimidating), but once you have the covers off, it is quite straightforward. Just keep track of the bolts, and take plenty of pics.

If you are doing it yourself, there's no need to replace the water pump unless it feels loose, notchy, or is leaking. If you do decide to replace the pump, expect broken bolts, that have to be extracted!

I'm planning on a wide selection of penetrating oils on my shelf, PB blaster, Liquid Wrench, WD40, Kroil, Breakfree, and anything else that I find. Marvel Mystery oil I may start buying in gallons. ;)

I don't know if this broken bolt thing is something everybody does, or if some people get a feel for it and rarely if ever break one.

so it's pretty common to break the water pump bolts? I can only imagine how much fun it is to extract them.

The mounting bolt (and boss) on my alternator was stripped by some P.O., so I've been looking at different ways to fix that..but i didn't have to extract any broken bolts!

I recently changed the TB and other WYIT items on my 32v. I did not find it to be that bad. In fact, it is not hard with the TB/WP manual I bought off Ebay for $18 and the above-linked write-ups. The manual is step-by-step.

There are a lot of things to remove from the front of the engine, but staying organized and taking your time, it is actually fun. I was able to complete the entire project (including meticulous cleaning) within 4 evenings. Next time, within a Saturday.

The manual I am referring to is for the 32v, but will work for 16v. You will have less steps to follow.

Rent the Kempf tool and flywheel lock and you are good to go with basic tools.

If you run into a snag, post a question. Key is to have all of your supplies before you get started.

I recommend you spray the whole front down with PB BLaster 2-3 times over a couple days PRIOR to starting this job, it will make your life MUCH easier
my flywheel lock and kempf tool are always available for borrow to anyone who needs them, I do require you pay shp and a deposit (not that I don't trust people) and I prefer that you not ask they be sent weeks before you're ready
order EVERYTHING to do the job, if there's something you don't need this time, return it or set it aside for the next change
and be sure to retension after 1500 miles, and check it every 10k after that

Just to stir the mud a bit, with a 81 project car, you might want to do what I decided to on my 83, pull the motor and do all the stuff at once, new silicone oil pan gasket, new motor mounts, new Euro S motor, new mortgage, all the basics.

i saw that 32V manual on ebay..is it really the same for 16V motors (minus a few steps)?

surfdog, the reviews and comments I have read would indicate yes, it can be used for the 16v, minus some steps.

However, I would email the guy directly (from his ebay add or rennlist) and ask him. He seems very straight-forward and honest. See what he says...

I 'm drawing a blank on his name right now.

Piece of piss the hardest part is undoing the crank bolt if its not a manual, you should not break any bolts loosening them just dont strip any tightening them you will need to remove the dipstick tube and case breather pipe so will lose oil.Set engine at tdc with timing marks lined up loosen tensioner pull belt the cam shafts will want to find their own position but u can reset as u replace .the belt tensioner bearing and water pump are the most important replacement parts if in doubt chuck it out and if the tensioner rubber boot is duff replace good luck P.S. the bolt holding tensioner on water pump goes into waterway so you will lose coolant when u remove it. P.P.S re hard to shift bolts give them a good whack with a hammer on top of the head it shocks the thread and stretches them it can loosen the most stubborn if you can get on to it and deliver a good belt

well it was not an encouraging evening last night..I got my locks back from 928 international (re-keyed)..the drivers side i got back in no problem..on the passenger side i got the lock in (finally) but something is interfering with the mechanism when the side screw is tightened..so it won't turn<aarrgh!>

This is the kind of simple stuff that kills you sometimes...i had dismantled the entire lock/handle mechanism on the driver's side (broken handle) and rebuilt the passenger side window lift system (motor, gears, etc)..so i guess i was getting cocky

Now I can't get the &(**%$# lock in!

well a little break is usually a good thing...i went into the garage last night and the lock went right in no problems....so sometimes you just need to walk away

You got that right. ;)

Take a break, work on something else, post a few questions, and time seems to improve the situation.

My point to you all: You are dealing with a cobra.

That 7 foot black rubber thing that we call a timing belt? It can BITE. And if it does, you'll not be staring at a pair of red marks on your hands or ankles- you'll be staring at a Porsche that needs major engine repairs! Major engine repairs that can run upwards of $8000 if you can't do most of the work yourself~

I sat in front of a Porsche certified mechanic who had changed dozens of timing belts, and let him show me how to change the belt on my 928. I learned a lot!

-I have a love it/hate it thought on this job. In 2008 it will be four years since I changed my belt, and though I'm way, way below the minimum mileage for the change...I'm still up in the air on this, and ready to take the car up to Orlando and have Donnie at Zotz Garage install timing belt #3 on my car. He's done two with perfect results so far. I cannot recommend this man enough!

My point: Let someone show you how to do this job before you try it yourself. NO, it isn't something so exotic that you can't do it yourself, but just like aviation...it isn't dangerous. It is just VERY unforgiving of any carelessness or neglect.

N!

Have any timing belts broken without some other part being the real cause? Water pump seizes, shoulder bolt bends so the belt rubs, or a tensioner fails and the belt skips teeth. None of those are direct failures of the belt or related to the age of the belt.

On a non interference motor, any US 16v, I'm not sure I would replace the belt with low mileage any time before 6 or maybe 8 years unless inspection revealed wear or any other problems with the water pump etc.

With a Euro motor I was thinking at first of changing at 4 years, but now I am not so sure. I'd like to know how well the valve relief in the pistons work, how many degrees the cam could be off before metal to metal. If I get the chance I may clay my heads and do some checking.

for Danglerb pockets in pistons are not for clearance incase of belt break they are there fore piston valve clearance in timing circumstances my 86 cost the previouse owner 13k nz to repajr after belt break in 1998 .In saying that you can be a bloody long way out before you get interference like putting the main timing pulley on back to front and setting the timing.Then you get slight interference doing this thats why you roll it over after setting the timing so as to feel for interference.Set it roll, over 2 revs check marks if lined up let it rip.

p.s. If you realy want to do something dumb set any piston at tdc and try to roll the camshaft one rev dont push your luck but back off if you feel resistance if you can roll 1 rev then chances are you have a none interference motor lucky b-----d

p.p.s Cambelts dont just break some just root the teeth off thats just as bad ,if you dont have deep pockets replace belts check tension REGULARLY.

JIM T NZ

32v I have no idea, but on the Euro 16v the piston cuts seem much deeper than clearance in normal operation would require. The valves are up in the heads from the deck and IIRC the lift is .474/.432 int/exh. If I get the chance its something I intend to measure.

I am buying a timing belt fail Euro S motor with valve damage, so that chance may come soon.

I've taken advantage of the fact that mine is not an interference engine to run it some while I troubleshoot other problems..but I have absolutely no history on this car, so the belt could be the original one. I think i've decided to let the mechanics have this first round, will let me focus on the other things that still need work..sunroof, gauges, etc etc.

When i take it to them I'll have them look at the rest of the drivetrain..I've always held out that if the basic repair things cost too much I would just get rid of the car (but working on it already I'll probably end up being one of those doofs that pays $10k in repairs on a car that's worth $7k)

How experienced is the shop you are using with 928's?

Most of the timing belt problems we hear about, except for pure neglect, are shops that made outright mistakes or just shoddy work. Do it yourselfers also make mistakes, but they tend to be detected immediately and corrected.

What motivates me to try it myself is the LOAD of while your in there work thats more time consuming than skilled.

There is nothing to screw up on a belt change on a 928 the hard part is removing the crap to get there. Then line up the timing marks pull the old belt off fit newbelt check timing marks (if you know where or what they are)roll over 2 revs recheck marks. Most important water pump and tensioner bearing if in doubt chuck it out. Belt tension is important but not rocket science I use belt deflection of about 4mm on longest run its easy to check regularly remove belt cover on rh side check tension .Try doing a 911 with a dti and clocking it in or even an aston martin dbs.

I think you've got it right jsbc, replace everything you have any doubts about. Most shops want the car in and OUT, not opened up taking a service bay with parts all over waiting for a new tensioner boot or water pump bolt to be shipped, so the old one goes back in, and the bomb starts ticking.

I may compare a few different ways of measuring tension including recording the tone of some segment of the belt when plucked like a guitar string. Once you have a reference its supposed to be very accurate.