Unusual Noise coming from engine compartment

[1980malibuman]

I've got a stock '86 GN with no mods, 145000 kms (90,000 pampered miles by the two previous owners and no winter driving) and it has been occasionally making a loud thumping (almost like a hydrological locking condition) noise coming from under the hood when trying to start it up, especially if the battery is low after sitting for a few weeks. I hadn't started it in over a week and this last time I did, it started fine without the weird noise but it made a rattling noise (like the exhaust thumping against the floor and/or a rattling noise like something loose in the exhaust) when driving it normally. Even just sitting in gear with my foot in the brake it was doing this. I jacked the car up and put four stands underneath so that I could run the engine in gear with the e-brake on while listening to the noise. The car almost stalls when these loud rattling/thumping noises starts and the engine shakes. It did this almost in cycles and each time the idle would be erratic, the car seemed to be stalling out and you could hear the loud thunking noise coming from the front of the engine and violent shaking then it would settle down and run fine. It seems to be coming from the water pump or turbo area. It has an off idle hesitation since I bought it but has run otherwise fine. I've owned the car for almost a year now and don't know much about Turbo cars. I replaced the plugs, air filter, and have been using 10W30 Castrol Syntec in the engine. This summer I took it to our local race track twice, with 93 octane fuel and added 5 US gallons of 110 race fuel, opened up the exhaust behind the cat and made 12 or 13 passes on drag radials. The car ran great with a best time of 13.94 @ 97.35 MPH and a 2.0 second '60 foot time. It did have one run in the eliminations that produced a 1.8 second '60 foot time (I'm not sure what was different on my launch) but I lifted before the end of the 1/4 and the car ran a 13.96 @ 78.54 MPH on a 13.90 dial in. The car was running fine after it was raced, but recently I hooked the exhaust pipes back up to the cat and changed the tires back to the street ones before taking it out for a ride. Anyone able to shed some light on this problem as I'm afraid to drive it now. Thanks.

 

[scottyb]

Just a thought (although not an actual solution). The noise you hear could be the result of the engine running poorly/shaking. (in other words it's a side effect). My IC shroud used to bump against the sway bar and make a thumping noise when the engine was running poorly/shook.

 

[1980malibuman]

Thanks Scott I will check out that out, but there is still a rattling vibration when driving the car now that wasn't there before and it seems to be running smoothly?

 

[stack1]

Do a little searching, alot of people have asked about engine noises. Take off the belt and start the car to rule out any accessories. Although you said it's coming from the front of the engine, I thought the same when I had a rattling noise magically appear. I checked the torque converter bolts, they were loose. Problem fixed.

 

[1980malibuman]

Thanks I will check those put too!

 

[Boost231]

Do a little searching, alot of people have asked about engine noises. Take off the belt and start the car to rule out any accessories. Although you said it's coming from the front of the engine, I thought the same when I had a rattling noise magically appear. I checked the torque converter bolts, they were loose. Problem fixed.

+1 try this and let us know.

 

[Boost231]

del.

 

[Silver Fox]

del.

Boost - check your PM.

 

[1980malibuman]

I just started it up again with a fully charged battery, and it ran fine for about 30 seconds and then started to miss and shake, then rattle. I put a long screwdriver to the turbo housing and it sure sounds like that's where the noise is emanating from. Then the car stalled out after running for about a minute. Is it possible that the turbo could be making all that racket? If so what's the issue? That could explain why it sounded like the noises where coming from the pass side when I was driving it on Sunday.

 

[chrisgarrett]

Just a shot in the dark, but what about your catalytic converter? It could be clogged. Take it back off and see what happens.

 

[1980malibuman]

I actually had the exhaust disconnected behind the converter, a fellow Turbo-T racer told me to try racing it like that.

 

[Boost231]

ever figure it out?

 

[1980malibuman]

No time to look at it today. I'm thinking that it isn't the converter as the car was running fine before I went racing and it ran fine when I unloaded it off the trailer and drove it in my garage. Now three weeks later after getting back from Palm Beach, Florida with a 1986 and a 1997 Turbo Regal, I finally drive it and this happens. I'm really at novice at computerized and turbo charged cars. When the car started up OK and ran fine except for the noise which I attributed to the exhaust system b/c I had it disconnected behind the converter when I raced it. I took it out for a 15 minute drive and noticed the rattling noise, so when I got back I jacked it up on all four corners to check the exhaust. It now seems to be going into this weird vibration/shaking mode and wants to stall out after 20 or 30 seconds from initial start up, which it did last night when I tried it again. I can't see it being the torque converter bolts being loose either as it is running rough and stumblling badly at idle in park after starting it up. I beleive that the noise is coming from the turbo. I put a long screw driver to various points on the engine and put my ear up to the screw driver when the car was running. The noise is definately louder at the turbo outlet housing (still has the shroud on the turbo) than anywhere else on the engine. I'm basically at a loss with this. I have never experienced anything like it before and other than the this noise was present last fall when I first bought the car and let it sit for a week and the battery drained down. When I went to start it it made the same noise before the battery gave out. I assumed that it was like a hydrolic locking situation when the engine was ckranking over without enough power from the starter. I re-charged the battery and it was fine. It has made this noise since when I let the car sit and the immobilizer drains the battery down. I think that maybe racing it has made the problem more apparent and the battery is fully charged so something has changed. But what???

 

[1980malibuman]

Is there a way to gut the factory converter? If so how do you do it?

Barry

 

[Boost231]

the factory cat? sure all you do is get out your tire iron and knock out all the material.

 

[1980malibuman]

Finally got a chance to check the conveter bolts and they weren't as tight as they could be, so I snugged them up and the noise is gone. Thanks for the advice guys. It's idling rough still which maybe b/c it still has the original injectors?

 

[stack1]

For some reason the noise that comes from the converter bolts being loose somehow seems like it's coming from the front of the engine. I didn't think the bolts were causing my noise either, but they were super loose and when tightened up, the noise went away. As for your idle issues, get a Turbo Tweak chip and it will idle smoothly.

 

[1980malibuman]

Thanks Stack1, I have talked to Eric from Turbotweak regarding my '87 Turbo T. I posted a message on here a week or so ago about that car when it refused to start after driving it back to Winnipeg 2300 miles from West Palm Beach, FL. I will talk to him about a chip for my GN.

Barry

 

[incharge]

Check the Harmonic balancer, could be loose or cracked...

 

[1980malibuman]

On which car, the '87 that won't start or the '86 GN that idles rough?