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May 12, 1999: Approximately 100,000 miles on the second engine. I've been wondering for a while now as to whether to change the timing chain or not. Having discussed the pros and cons with various folks and still not coming to a definitive conclusion I finally decided to do it anyway. As it turned out... it was an excellent decision. I'd like to thank Claude from Victoria BC for his timely reply to the GMCnet outlining his experiences in changing the timing chain on his own GMC. Following his recommendation with reference to jacking up the rear, the airbags were raised fully instead while the antifreeze was drained via the radiator draincock. A heater hose was disconnected so that air could get back into the block helping to drain it all. When it was all drained the airbags were fully lowered, squatting the rear of the coach down before waterpump etc. was removed. This prevented undesirable cooling fluid dribbling when it could be getting into the oilpan while it was exposed. The split fan shroud and serpentine belt made for relative easy access to the front of the engine. However... it's certainly not a job I would've liked to do by the side of the road somewhere.
Timing cover removed, chain exposed.
Does it look ok?
Not...
Timing Chain and sprockets removed. Rags cover the opening to the oilpan so that it stays clean. Oil will be changed anyway but no use adding extra chunks.
A piece of the normal pit planking was used to locate the two jacks
to support the front of the engine. A piece of 2x4 was used under oilpan and the second
jack was placed under the final drive, also with some wood for extra protection.
The new Cloyes True-Roller timing chain set was ordered from Mondello, more or less based on monitoring discussions and threads on the GMCnet. I also ordered the Camshaft Thrust Button & Bolt, Water Pump and a Camshaft and Lifters. I also meant to order the water restrictor kit but they sent me the oil restrictors instead. Guess I'll be running with the 195 degree thermostat a while longer. No complaints though... it's been working just fine. The Water Pump I'm still having a little hard time to justify to myself as
I went for the Heavy Duty, Super Duper, Maximum Flow, etc. etc. etc.... at 399 bucks. May 13th corrections: As it turns out I didn't get the
monster described above but rather the regular for $99.00. Seems Tech Guy gave me the
wrong partnumber to pass on the order taking person and I didn't catch when or whether the
price was read back to me. Oh well... :-( The Camshaft and Lifters I purchased on the recommendation of "The Tech Guy" at Mondello's. When asked if it would be possible to install the camshaft without any extra dismantling he said yes. Well, I don't think I received good advice on that one as I can't see how it can be done. Perhaps I'm wrong and I just consider it beyond my capabilities. That could be, and as I consider myself a reasonable judge of those capabilities I'm going to leave camshaft and lifters alone. The Camshaft Thrust Button however did get installed as it was the right time to do that. May 13th correction: As I ordered the Camshaft, based on their recommendation, I also got the "button" for install with camshaft instead of the "button" to install if camshaft already in place. Did luck out on that one though as our clearance seems just right, except that the sprockets have to be removed so that the spacers can be removed. Thirty bucks+ wasted on shims. Lesson learned by all this: Order the catalog first as that seems to be the only way you're going to be able to order what you really intended to order. Unfortunately the catalog is '97 vintage so some newer stuff may be available that is only in the pricelist and not superbly described, i.e. not, other than back to verbally.
New chain and sprockets in place.
Notice that the new chain is tight and without play. The old sprockets were lined up prior to removal but when the new one was installed the crank had to be turned slightly to get it all lined up. In other words no more slack in the works. I can hardly wait to have it running to see if there is any difference in noise... and of course performance. The check on performance may have to wait a few days as there is an exhaust gasket to change as well as a new alternator going on, now that the pulley problem has been identified and a work-around devised. Next time the change will be made at 75,000 miles... just to be sure. Comments? Questions? Drop me an email.
Mondello's website is: http://www.tcsn.net/mondello.
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