JEC_31

I am memorizing John Pirtle's most excellent write-up (at http://members.rennlist.com/pirtle/tbelt.html ) while waiting for my timing-belt-extravaganza 928 Intl order to arrive, and I have two questions that he does not elaborate upon:

1) Are there any important details to rebuilding the tensioner? I had merely planned to carefully disassemble it, gently clean it, replace the o-ring, and reassemble in reverse order. What can trip me up?

2) Is John correct, and if so why, in that the oil is filled AFTER adjusting the newly installed belt tension?

Thanks in advance - and thanks to John for great technical writing and pics!

Garth S

In the category of 'too simple to mention - but it can happen' is the insertion of the piston after replacement of the O-ring: if dropped in backwards, the ring passes beyond the bore( trapping the piston).
Beyond getting the washers in correctly, the only critical step is to assure that each rod/bolt/piston/etc. is fully seated in its respective cup/socket.( some reports of difficulty in getting the T Belt to fit were due to this).
The issue of filling with oil as the last step I had assumed to allow filling the maximum internal volume after the tension was applied - however, not sure if this vol. actually increases as the tensioner bolt is cranked in!

Gretch

Re your second question, from a theoretical perspective: the oil is the heat transfer media to the bi-metallic washers. As the block expands from heat, the washers change shape to slack the tension on the belt. Given this description is accurate, I cannot think of a scenario where it matters when you put the oil in the tensioner, only that you be sure and do it.

The exact order of the bi-metallic washers is important. when you take them out, remember howthey came out. Put them in the same way.

worf928

As above and:

filling the tensioner part-way with oil makes it easier to fill completely after you've installed it. You will need something to pump the oil into the tensioner. I've got a little hand-pumped oiler with some small ID clear tubing.

Also, I've done two t-belts now with JP's instructions. The one thing I'm going to try next time is installing the tensioner _after_ the idler carrier. It's a pain to install the carrier after the tensioner 'cause you have to fiddle with the spring-loaded rod to seat it in the carrier while pressing the carrier into the water-pump _while_ getting the t-belt routed.

Lastly, don't accidentally allow the conglomeration of bi-metallic washers to fall out of the tensioner as you describe to your neighbor how the tensioner works. DOH!

Chris Lockhart

Hey David, I learned a couple of months ago that it IS easier to install the tensioner AFTER the idler arm. I had done the entire t-belt/water pump/tensioner rebuild, and got to the step on filling the tensioner with fluid. Damn thing leaked like a seive. Apparently when I had wrangled the idler arm into place, I tore the tensioner boot in several places. I got a new boot and mount gasket and proceded to take the tensioner off. Installed the new boot, and then installed the tensioner w/ the new gasket. Much easier to get the plunger into the tensioner when you're coming in from the side. Finished the job all up, w/ no more leaks. Got about 3K on it all now, and have had no problems whatsoever. BTW, I love your avatar. BEEEYOOTIFUL engine!!!!!!!! (I'm Guards Red from envy!!!!!)

JRich

Timely discussion as I'll be needing to this job this fall at my current rate of yearly mileage. Thanks all for the in-depth coverage on the subject.

I read John Pirtle's excellent Timing Belt Procedure, loved the pictures, (I need visual aids like that) as well as the other sources listed. My question is are the procedures relevant for ALL model years, or are there differences? If so, is there a place detailing those specifics?

TIA

am

Hey Gretch, you wrote : The exact order of the bi-metallic washers is important. when you take them out, remember how they came out. Put them in the same way.

I'm not finished rebuilding my tensionner and i did'nt check how were the washers before , is there a documentation or link somewhere that could help me to put them back right ?
Thank's

Garth S

AM,
Vol 1, pg. 15-22 of the Factory WSM has the washer sequence. Wether it is a 35 or 40 washer unit, they're always assembled in symmetric groups of 5, and stacked in these groups to maximize the column height. (it's clearer when you look at the pic)

Rez

JEC,

When I rebuit mine, I replaced everything... rollers, boot, clamp, oil. Depending on the model, you may have to replace the o-ring and gasket depending of the MY. It may seem like a couple extra bucks, but it's definately cheaper than belt valves. I've attached a pic of the washers. With many things of the car, to be sure I don't screw up bolt locations or this case the order of the washers, I install zip ties to hold them on. The also works great for the different bolts on the cam covers.

Rez

JEC_31

Wow - I love this forum. An outpouring of well-written technical info and pictures from a couple simple questions - amazing.

Thank you guys!

Yes, Rez, I am replacing/rebuilding absolutely everything I can.

After reading (on this forum a month or so ago, who was it? Same year & similar mileage as mine...) about the horror that happened to someone's motor when their mechanic skipped a couple little details, I decided: 1) I'm not even starting the thing until I 2) replace/rebuild EVERYTHING.

worf928

Excellent! I tell ya, my back was killing me after 30 minutes of bending over futzing with the thing.
I'm of the opinion that if you're going to spend 20+ hours bent over R&R-ing and cleaning gunk then you might as well spend the extra $100 and replace the rollers, o-rings, bushings, gaskets, etc. When I did the belt on the '91 over x-mas I was surprised to find that of all the parts that were R&R'd that it was the smaller roller that was toast. Wasn't rolling very well at all.
Thanks Man. I did all that on the '89 with the engine in. Next time (i.e. for the '91 in about 4 years or so) I'm going to pull the engine as step #1.

Also, I'll trade you my pretty engine for your dyno numbers. My POS '89 (aka "Walt") is still not making power at the top. But, now with the '91 back on the road I can turn my attentions back to Walt.

Chris Lockhart

Hey David,

I actually did replace all the rollers, etc...., and I removed and rebuilt the tensioner. It was during the rough install that I tore the new boot, and had to get "another" new boot and gasket. I didn't state that in my "condensed" version. (Sorry.) I can't see going to all the trouble to go in there, and not doing everything you can. I hear of folks doing it all the time, and even of shop mechanics not replacing these items. Borderline criminal to me.

Well that sucks. Any idea why not????? Mine could pull out a few more ponies if I could get her to richen up some.

worf928

Aaahhh! I got it...
At this point it's either the throttle position switch, LH harness, or a missing (as in removed) cylinder My bet is on both TPS and Harness. Especially the harness since I had it off except for one connection and the pull through the fire wall bit and Murphy just really likes to mess with me. As soon as it gets above 0 degrees F and I get a few hours. Got all the manuals, multimeter, oscilloscope,...
I can help I've got an old MAF that's due for a rebuild - so it reads lean and makes the LH dump more fuel in. 'Course a beefier fuel regulator is probably more what yer lookin' fer. But the old MAF got my '91 in the the 11:1 range last time on the dyno - talk about rich.

am

Thank's Garth S for the info.

Gretch

am, you got a complete answer to your question.....It is not that I was not paying attention to your question, I was out trying to earn a living yesterday. This is the best place for no-bull**** technical advice on a 928.