About Us

Tom63LeMans · 06-30-2005, 02:31 AM

I have a '94 GTP with the 3.4 DOHC. The timing belt broke which I've replaced along with all of the idler pulleys, tensioner pulley and tensioner. After starting the engine there is a loud rattling noise coming from the belt/pulleys. I've tried 3 different tensioners and 2 sets of pulleys and 2 different belts but noise stays the same. The other problem that started at the same time is the engine hardly cranks over when hot. Cools down and starts fine. Also has a slight vibration at idle. Any help would be appreciated. I'm about ready to drive it off a cliff.
Thanks,
Tom

Mark O · 07-01-2005, 04:37 PM

I may be wrong, but I always thought that the 3.4 DOHC was an interference engine. Have you by chance done a compression test?

Tom63LeMans · 07-01-2005, 07:23 PM

It's listed as a clearance engine but from what I understand it's only about .010". The belt broke at low speed and there was no noise but I have not checked compression. Runs fine off idle. After running for about 10 minutes pulleys and external cam journals are pretty hot. The noise seems like it is coming somewhat from all of the idler and tensioner pulleys. Almost seems like something is bent but I can't see anything visible. I've been driving it but it will not crank over once it's hot.

TIAUTOMAN · 07-01-2005, 11:06 PM

Twothings
is the power the same before and afte3r the belt change?
there are several timing procedures out there and someof themare wrong
Second
did you remove thecam gears? or loosen them to letthem spin?
if you did, there are locks inside the gear that should be replaced
THIS will cause a knock/rattle noise
I have done dozens of 3.4 timng belts,never had a bent valve issue.

Tom63LeMans · 07-02-2005, 06:52 PM

The engine seems to run fine but like it is tight. I pulled the covers and locked the flats of the cams on straight top position. I have not loosened any of the cam pulley bolts and they are tight. I have noticed that the lower drive pulley can be rotated slightly and makes a rattling noise. I tried to loosen that bolt to pull off the pulley but can't get it loose. I thought that the noise I'm hearing might be the slack in the chain and the tensioner compressing on the inner timing chain. Travis, have you ever noticed play in that lower pulley? What concerns me is the getting tight when at temp. I thought maybe the tensioner was too tight. But then one of the umpteen times I had it apart I left the holding pin in the tensioner and it made more noise when loose. I'm at a loss. Thanks
Tom

TIAUTOMAN · 07-04-2005, 02:27 PM

if the tensioner is to tight it will make a noise
whirring noiseto a ticking type noise
did you replaceall the idlers? If not should have
the lover (cog pulley) is free floating ( not keyed). bolt holds it on.
If you take it off its a pain in the ass untill it pops then will spin freely on and off.
ITS NOT A PRESS FIT.

Tom63LeMans · 07-04-2005, 04:52 PM

First time through I put all new idlers and tensioner pulleys on. Later I changed back to originals and it was slightly quieter. I'm not sure what to do next. I thought maybe it would break in and get better but it's not. I may try taking apart one more time and see if I can tell what is getting tight. Have you ever seen a problem with cam journals?

TIAUTOMAN · 07-09-2005, 12:00 PM

No
Never
but that doesnt mean it cant happen

Tom63LeMans · 07-09-2005, 01:03 PM

I found out the source of my problem. I installed the belt while the cams of both heads were locked in position with the flats up. This is the way they are shown in the GM shop manual. I found a post on the internet that described a procedure to set the pulleys on the front bank. I loosened the front bank cam pulley locks, turned the crank 360 degrees and locked the pulleys back down. It runs like a top now, no noise, vibration or hard starting. I went back to the shop manual to see if I missed something and cound not find any mention of the cams having to be set in this manner. I learned a valuable lesson about relying solely on manufacturer's documents. I still can't believe the car ran with one bank out of phase and didn't set off any codes. Thanks for your help.

TIAUTOMAN · 07-09-2005, 02:35 PM

In my earlier post I had asked about the timing procedure.
The GM manuals are wrong on the timing, thats why I had asked what timing procudure you used.
Normally when both sets of cams are timing with the flats up the is a lack of low end power ( I know first hand, before finding the revised timing procedure years ago).

Im glad you found your problem

Menu

About Us