Clue (?): Shortly AFTERI paid a local shop to replace the oil pan gasket and water pump (both leaks fixed) I noticed a mysterious noise from under the car. Will hear nothing unusual for several miles then little bangs which get bigger, go away, come back without getting bigger, etc. The worst are loud and actually vibrate the driver seat. Recently I've noticed they are worse when turning, especially turning left. Yet at other times I can cruise and turn with no unusual sounds.
The car has been up on lifts three times looking for the source/problem and I've crawled under a couple more. No, there are no branches caught in in the undercarriage and there's no other obvious cause.
First diagnosis: the connectors between the rear sway bar and the A arms had evidently never been changed. They looked like skeleton connectors, pads worn almost away, and could easily be flopped back and forth. So with the guidance of Forum members I bought some new connectors and had them installed. Felt great when I drove away . . right up until the noise came back.
Second diagnosis: Guy showed me. The exhaust was rusted through in a few spots anyway, but it was also rubbing against the outboard metal of the "frame" (cradle?). A spot had been rubbed clean of rust. So with the guidance of the Fiero Store, I bought an Ocelot exhaust system and had it installed. Felt great when I drove away. Sounded better. Then I heard the noise come back. Another Clue (/) - the exhaust installer re-used by cutting and welding the flat metal support "studs" from the old exhaust onto the new: "They are already grooved to fit the mounting springs".
Third diagnosis: When the exhaust installer guy had the car up the second time, he noticed the connectors from the front sway bar to the A arms was loose on one side. Clue (?): I had replaced those connectors my inexperienced self a few years ago WITH both inner and outer tie rods AND the brass replacement for the steering rack bushing. The installation shop obtained replacements and installed. Felt great when I drove away . . right up until the noise came back.
Related? Exhaust installer also said the motor mounts are worn down and the engine might have more than normal movement.
I have another appointment with shop which installed the front connectors, this time to drive a mechanic around so he can listen.
Can anyone think of what I'm missing in this click- click, pop -Pop, bang-BANG, then quiet for a while mystery?
Iffy engine/trans mounts is very bad. Noise is only a Warring.
Engine moves can have: Pulleys and belt hitting Alt and other parts can break Exhaust will break Intake parts can break too w/ some engine like Fiero L4. Wires can make noise before shorts out or breaks.
If Trans moves Sideways etc, Inner CV(s) can have problems. When you turn, One Inner CV is compressed hard, Other is pulled out. Ether can made big binding and noise problems. Out out too far will destroy the CV instantly. The axle then destroy other parts and/or lock the wheel depending just what loose end of axle hits.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
I'm waiting now for the Fiero Store to open so I can order - and please check me on this - front engine mount ("after market", much less expensive than "OEM") rear engine mount two transmission mounts (stock type OK for 4T60?) "dog bone"
Fiero Store prices are reasonable. The Ocelot exhaust they sold me seems fine.
I'll suspend driving the 88GT until the slow and steady drive to the installing shop.
Add to the ever longer list of parts bought and installed in the pursuit of fixing the still mysterious clanking sounds under the 1988 GT (with 3.4 push rod and 4T60 trans): Motor and transmission mounts (including "dog bone").
Shop test drove car after new Fiero Store mounts installed. No clanks. Shop said the old mounts were really worn down. I drove the car home. More "dramatic" engine sound and nice vibration, as expected. No clanks! Great! Then at about seven miles the first little clink. Then more. Then the louder clanks, just as before. Clinks and clanks when driving level and straight but more when going through "dips" in the road. This time not such an evident increase in clanks when turning from our shared lane into our driveway.
Although the "best exhaust shop in Bloomington, IN" guy who noticed the motor mounts being worn down while installing the new (Ocelot, from Fiero Store - only source I could find) exhaust system obviously thought he'd done a great job hanging the new exhaust, I'm still suspicious of the exhaust system as a cause for the clanks for these reasons: 1) Clink/clank noises (and clank associated vibration which can be felt through the driver seat) ONLY START AFTER SEVERAL MILES, i.e., after everything is fully warmed up and fully expanded. The "best exhaust shop" guy showed me a rubbing point on the old exhaust before installing the new. 2) Exhaust installer re-used the same pieces (flat rectangular steel with notches to match the hanging springs) used by the old exhaust system by cutting them off the old and welding to the new. 3) More than a month ago while I was on my back under the car with a rubber hammer banging on everything I could reach, the sound which most resembled the while driving clanks was when I hit the exhaust near the engine.
Other information: the car has not had a catalytic converter since at least as far back as 2005. The new Ocelot exhaust only extended "from cat to back of car" so a new straight length of exhaust pipe tubing was welded in where the cat would have been located, just as was done for the former filler piece in the exhaust system which was just replaced. I don't know if the length of the old or new filler pipe was exact. A too-long piece mistake could have been repeated. Loose/worn motor mounts and resulting engine movement started the clinks/clanks by pushing/pulling against the exhaust system and compounding the mistake???
What do you think about arranging to pick up the exhaust guy and taking him for a ride AFTER the car is fully warmed up and clanking? He hears it, then we return and immediately put the car on a lift and look?
------------------ John W. Tilford
[This message has been edited by John W. Tilford (edited 04-25-2021).]
Originally posted by fieroguru: It sounds like one of your axles shafts is a little too long or too short. As the suspension cycles going over large bumps or turns, the inter tripot starts to angle and bind on the tripot housing.
Or Trans have moved sideways doing same thing. As that can/will stretch one and compress other axle even rest not running.
Look at all pulleys too. If even 1 pulley is close to frame that should, brand engine/trans mounting allow a little sideways play and pulleys other things hit. Exhaust and some other parts grow when hot too and may hit somewhere.
Brake and suspension parts can do same when hot and noise is problem w/ them not engine problem.
The Meineke shop which just installed the motor/trans mounts said they "checked the CV joints" as I had requested and could find nothing wrong. Of course, I'm not sure how they checked or how much they know about Fiero short and longer axles. Probably more than I do. How could I or a professional check what you describe?
Also, I wonder how I could hear no clink/clank at all for the tens of thousands of miles since the 3.4 and 4T60 were installed until earlier this year? (Although, the extensive labor for changing the oil pan gasket and water pump and belt cover did suspiciously precede the noises.) And what would explain the several miles delay each time I drive it before the noises start?
Finally found a possible cause - or maybe just a result - of the clicking and banging. Here's an image showing where apparently at least two spot welds have failed and the layer of steel closer to the smart phone camera has been sliding against the layer underneath:
Back side, as seen from the left rear wheel well. Seam is just to the right of the two wiring protector deals:
The location is behind the driver seat and near the outside of the car. The mechanic who spotted this was able to use a small crowbar and move the closer metal up and down. The counterpart seam on the other side of the car is fine.
I've got an appointment a week from now for the local GM dealer body shop to try to weld. Doubt they can access well enough to drill and replace spot welds, probably wire weld along the seam on both sides, maybe add a short piece of angle steel and weld that over the seam.
BUT, is the failed seam the cause of the noises or one result of the banging? The 3.4 has additional torque, sure, but enough to cause this? I doubt it. Or do these spot welds just plain fail sometimes?
Remember the clicking/banging only occur after a few miles. Drives like a proverbial dream until that with no unusual noises or vibrations. The loudest bangs I could feel under my butt.
Gary (GKDINC), 1) Only when moving 2) Only after a few miles 3) Sometimes associated with bumps in the road like RR tracks, sometimes not.
Maybe a clue: car consistently popped and banged on our shared lane when I returned home after the "several miles" drive prerequisite had been met. The lane is crushed stone with gazillions of little bumps giving a vibrator effect.
Regarding flex plate: no start up odd noises or apparent starter to ring gear issues.
------------------ John W. Tilford
[This message has been edited by John W. Tilford (edited 05-27-2021).]
Local GM dealer/suspension portion of service guy/"collision" shop welder guy (and they let me under the car while up on lift before they started and after they finished)
1) welded both sides of "break" illustrated above. Their better lit and angled view of the back side showed an actual gap between the layers of steel. Painted black after welding. I did not see the pre-paint weld, Hope it was sanded/wire brushed/whatever.
2) I asked the body shop guy doing the welding to also test/check around the four corners of the cradle, which he said he did. His words [paraphrased] "I didn't actually use a torque wrench but they looked OK".
Anyway, no clicks or bangs in the last three trips to town and back, average 8 miles one way. I'm still holding my breath.
Heard some of the same clicks and a mild bang yesterday. Crap. Much better, but still frustrating/disappointing. Makes me wonder exactly what I'm risking by driving the car. Takes the fun our of driving. I wonder what caused the spot welds to break in the first place.
What do you think about taking the car in to the last shop which actually lowered the cradle (I assume they would have had to) to replace the oil pan gasket and install new water pump, new belt, and new gasket around water pump etc. belt cover. All the leaks were fixed, but the click/clank/bang noises started after that work. Ask them to check each corner of the cradle? The GM dealer welder just looked at the cradle bolts and said they seemed OK.
Clanking noises can also emanate from a loose part in the exhaust or suspension system. Make a simple stethoscope from a funnel and a length of heater or garden hose. Duct tape the funnel to one end and that is your listening piece. Have an assistant rock the car and listen around. Also check the steering rod ends for excessive play.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "