1999 Chevy Blazer Knocking sound after extensive repairs

MALICE

MEMBER
1999 CHEVROLET BLAZER

Noises problem
1999 Chevy Blazer 6 cyl Two Wheel Drive Automatic 133k miles

I just had my blazer in the shop last week to have the intake manifold gasket done. They told me a few other repairs she needed, which I proceeded to do on my own with the help of a neighbor. I replaced the ignition coil, plugs, wires, distributor and cap. Went to drive her after repairs were all complete and the "check engine" light was on, so I took her straight to the shop where they found that my neighbor had forgotten to plug the distributor back in. Light went off, problem solved, but as soon as I drove off I noticed a very slight knocking noise. Barely audible over the hum of the engine. Drove her home, put it in park and the noise got much louder. Gets faster with accelleration (while in park). Sound is less noticable while in drive OR with the AC on. Tried to see where it was coming from but I just can't tell, sorta seems like it's in the front/top. Could something have been knocked loose during repairs? It seems unlikely something else major would have "broken" in just the time it took me to get from the shop to the house.
Thanks in advance!
~Malice

ADDED: Could it have ANYTHING to do with timing? We had to manually turn the engine to get the distributor to drop into place and my neighbor said it could be a tooth off in timing. Just wondering if this could cause the noise?

3 Replies

RACEFAN966

MECHANIC
5,029 POSTS

Yes it could be timing. I would first check to make sure the distributor is in correctly and make sure the timing is right. If all that checkes out then I would be an automotive stethescope so I could listen to the alternator and idler and tensioner pulleys and such to find out where the noise is coming from. Get back to me with what you find and we will go from there.

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Friday, March 27th, 2009 AT 10:08 AM

MALICE

MEMBER
2 POSTS

Thank you for your response.

We checked the distributor and fixed the timing and the knocking is still present. I don't have an automotive stethescope so I drove her to a local machine shop and had them take a listen. They told me it sounds like a bearing and quoted me $3k as a worse case scenerio to repair! He told me that due to the manifold issue (that was repaired last week), with water getting in the oil, this caused the bearing to break down regardless of the manifold work being done. So apparently it is possible for something else to have broken at that moment!

What I need to know now is; is there another way to repair this without pulling the engine out? And is this failure completely coincidental to the tune-up I performed the day before the knocking started, or could we somehow have caused this to break while changing the plugs/wires/distributor? Seems impossible to me that the tune-up could have been the cause since we werent inside the block! But my husband is insisting that it has to be my fault since I was working on her the day before (even tho he knows nothing about cars!)

Thanks again,
Malice

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Saturday, March 28th, 2009 AT 8:54 AM

RACEFAN966

MECHANIC
5,029 POSTS

Ok first off no finger pointing as it is not of anyones fault. Engines are mechanical and do anything at anytime. However I do agree with you that it seems kinda of odd that it just started at that point. Just to check the basics, you did double check to make sure that all the sensors are pluged back in and no wires got pinched under the intake or the distributor? Did you use a scan tool to check the camshaft retard offset? If not and you have a scan tool then let me know and I will walk you through it so we make sure the timing is correct. Also if you can use a metal rod or extesion for a ratchet and listen to the lower end. Meaning put it to the oil pan while the engine is running and see if you hear the noise they are telling you about. If it is there is will me loud then listen to the intake and see if it is louder or not. Get back to me.

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Sunday, March 29th, 2009 AT 10:09 AM