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Help! 84 coupe Metal sound after replacing rear main seal

AussieCorvetteNut

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Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
Hi guys,

I put in a new Felpro rear seal and one piece gasket today, as I have done a few times before.

The bell housing plate was a b1tch to get back on, but everything else was fine.

The oil pump and shaft went back in ok, the rear main went back on and I torqued it as normal.
Thinking about it, I am not real happy with the torque on the rear main, hoping that my issue isn't a main bearing issue.

I topped her up with new oil and a new K&N filter.

I cranked her slowly to help prime everything again and then let her fire up.

I have oil pressure, the top end would be rattling off its head if I didn't, but I was looking for a low oil light and forgot to check the pressure on the IP.
Just went back up to the shed and fired her up, yes oil pressure and good as normal.

I have a metallic sound coming from the engine. I reckon it is the bell housing plate.
I don't think there was a problem with the oil pump shaft, it seams as though it went back ok, it wouldn't have bolted back up if there was a shaft mismatch.

Dunno, got me buggered, thought I might post and sleep on it until the morning.

What do you guys think???????
 

AussieCorvetteNut

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Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
....bugger broken rear main bolt

What do you guys think???????


Well I pulled the oil pan off this morning and took out the oil pump and main bearing cap.
All looked ok, so I started to reassemble everything again and was torquing the main bearing cap down and snapped one of the bolts...:mad

After a fair bit of swearing, I calmed down and took the other bolt out and took the rear main cap off.
The broken bolt still has a few threads on it, so the other part of the bolt is al thread. I can't see any available thread to get the removal process started.

Have any of you ever broken a rear main bolt and what did you do to fix it?

:beer
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
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Messages
13,453
Location
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71 04 12 19
Let me get this straight...you broke a rear main cap bolt?! That ain't easy.
Geezus how hard were you pulling on the torque wrench and had you ever had it checked for accuracy?

You'll have to try drilling the center of the broken bolt then trying to get it with an "e-z out" tool. Drilling it won't be easy because those are really hard bolts.

If that doesn't do it, you'll need to get the motor out and disassembled and have a engine shop extract what's left of the bolt.
 

AussieCorvetteNut

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Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
Thought as much

Let me get this straight...you broke a rear main cap bolt?! That ain't easy.
Geezus how hard were you pulling on the torque wrench and had you ever had it checked for accuracy?

You'll have to try drilling the center of the broken bolt then trying to get it with an "e-z out" tool. Drilling it won't be easy because those are really hard bolts.

If that doesn't do it, you'll need to get the motor out and disassembled and have a engine shop extract what's left of the bolt.

Hi Hib,

Yeah that's right, broken rear main bolt...you kinda know something isn't right, had a bad feeling something wasn't right.

New torque wrench this morning, pulled both bolts down together, started at about 50ft/lbs and went up gradually to 100, then one side was good at that and the other broke.

I might try the easy out method, had a look and I can get to it no problem, but yes hardened steel isn't an easy drill.

While I was under the Vette, and since my last post, I have noticed 3 drops of green coolant towards the front of the block, sitting on the block face where the oil pan gasket is...mm where did that come from.
I am starting to think it will be engine out, and that is what I was planning at a later date, looks like it may be sooner rather than later.
I noticed that the old rear seal was dry and brittle and that the oil pan gasket was a black reinforced gasket. I know you did some testing of the 84's, do you know what sort of gasket they had then when new.

This C4 was eleven when it came to Australia in 1995 and had a conversion then, that owner had it for about 8 years and the guy I brought it off had it for 11 years.
Looks like I inherited their wear n tear!

The wife is not happy, I was supposed to get the Vette off the hoist to put O2 sensors in the Holden today.

I said that looks like the 84 will be a work in progress now.

I have rebuild kits for the Dana, the OD unit, the 4 speed and every suspension component except the sway bar bushings and the front tie-rods and steering rack, it's RHD so I have to figure out where the rack came from.
Parts for the gearbox are hard to find and getting the OD unit working again may be more trouble than it's worth, I might have to opt for a 5 speed aftermarket.

Appreciate your help and advice,

Thanks Hib.

Tony
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
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Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
Main cap bolt torque specification is 80-lbs ft.

Big oops, eh?
Poop happens, mate.

My suggestion would be to get a Service Manual which contains tightening specs. CAC sponsor Zip Products has them.

As I suggested before, you can try drilling into what's left of the bolt and using a bolt extractor. You might just get lucky. But if that doesn't work, pull the motor.

Also, replace the other bolt and any additional main bolts which were over-torqued.

As for the Doug Nash...Richmond gear used to list a conversion kit to put one of their six-speed in place of the 4+3.
 

AussieCorvetteNut

Well-known member
Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
...crap, I just checked the manual again!

Main cap bolt torque specification is 80-lbs ft.

Big oops, eh?
Poop happens, mate.

My suggestion would be to get a Service Manual which contains tightening specs. CAC sponsor Zip Products has them.

As I suggested before, you can try drilling into what's left of the bolt and using a bolt extractor. You might just get lucky. But if that doesn't work, pull the motor.

Also, replace the other bolt and any additional main bolts which were over-torqued.

As for the Doug Nash...Richmond gear used to list a conversion kit to put one of their six-speed in place of the 4+3.


Thanks Hib,

I just checked the manual again, the old measure twice cut once method does work when you apply it...I can't believe I made that mistake.
108nm is 80lbft...Had a really bad day hey.:duh

I figure I will do the ring around today for a mobile technician to come out and remove the rest of the bolt, if I can't I will get the easy out and have a go.

I will fast track order 2 x rear main bolts and going by the three drops of coolant that appeared, and no milky oil history, I reckon the coolant is a sign from the water pump not from the head gasket.

I have a new power steering pump coming, so will order the parts today.

Thanks for your help Hib, you can fix the car but you can't fix stupid hey!

:beer

Tony
 

ZZ1-70 LT4-96

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Feb 16, 2013
Messages
30
Location
USA
Corvette
1970 coupe 1996 LT4 coupe
bolt snap

Well I pulled the oil pan off this morning and took out the oil pump and main bearing cap.
All looked ok, so I started to reassemble everything again and was torquing the main bearing cap down and snapped one of the bolts...:mad

After a fair bit of swearing, I calmed down and took the other bolt out and took the rear main cap off.
The broken bolt still has a few threads on it, so the other part of the bolt is al thread. I can't see any available thread to get the removal process started.

Have any of you ever broken a rear main bolt and what did you do to fix it?

:beer

How much of the bolt is in the engine? All of it? With the bolt snapping and all threaded bolt in the engine block, there is a pressure being applied what is left in the engine. Have you tried getting it out based on no pressure, just part of a bolt threaded into the engine?

A very very long time ago working at a gas station I was checking a cars rear end lubricant and tightened the plug on the differential to much and it broke. I was very distraught and got my boss. He smiled looking at the damage and reached up with his hand and unscrewed the threads from the broken plug with his fingers and handed it to me. He did not even charge me for breaking the part.
 
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AussieCorvetteNut

Well-known member
Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
How much of the bolt is in the engine? All of it? With the bolt snapping and all threaded bolt in the engine block, there is a pressure being applied what is left in the engine. Have you tried getting it out based on no pressure, just part of a bolt threaded into the engine?

A very very long time ago working at a gas station I was checking a cars rear end lubricant and tightened the plug on the differential to much and it broke. I was very distraught and got my boss. He smiled looking at the damage and reached up with his hand and unscrewed the threads from the broken plug with his fingers and handed it to me. He did not even charge me for breaking the part.

I thought as much, so I had a scratch around in there, but the bolt is firm...it wouldn't be under pressure, that went when stupid broke the bolt...:L

I have ordered new main bearing bolts, they are on the way, and have organised a technician to drop by and drill it out.
Plan is to then put everything back together and fire her up.

My brother in-law and his Dad are also into Chev's and have two Vettes, and the old fella said the same, he said it may noy be under too much pressure now that it has snapped.

It will all be out on Friday...:gap
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
The bolt was over-torqued by 20 ft/lbs. It likely stretched and that tends to jam or lock the threads near where the bolt breaks. My guess is what's left of the bolt will need some "persuasion" to get it out.

On the Nm to ft/lbs conversion back when that car was made GM had not gone metric in its service manuals. Several years later it began to publish torque specs both ways.

It's an easy mistake to make if you don't have a torque wrench with a scale in both units of measure.
 

AussieCorvetteNut

Well-known member
Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
Stretched Bolt

The bolt was over-torqued by 20 ft/lbs. It likely stretched and that tends to jam or lock the threads near where the bolt breaks. My guess is what's left of the bolt will need some "persuasion" to get it out.

On the Nm to ft/lbs conversion back when that car was made GM had not gone metric in its service manuals. Several years later it began to publish torque specs both ways.

It's an easy mistake to make if you don't have a torque wrench with a scale in both units of measure.

Thanks Hib,

100% agree with the bolt being stretched, when I compared the broken bolt with the bolt from the other side, I know it sounds funny, but you could tell there was a difference...and before anyone comments, yes the difference was that one was shorter...;LOL

The rest of the bolt is firm in there at the moment, but hopefully it will give way on Friday morning.

Hopefully will be able to put it all back together for now and plan the engine rebuild for another time.
I am always hesitant on putting old parts back in, but she ran OK before I pulled the main bearing cap off.
The metallic sound wasn't right the other night, it sounded like metal plate, I think it was the backing plate.

My water pump is on the way, it is in Cincinnati at the moment.
Funny how it is cheaper to get parts from another country, have them shipped to the other side of the globe and still be cheaper than buying from the retailers here...wish it were that simple with the Richmond gearbox swap...but that's another issue.
I remember when I was the Treasurer for the Queensland Corvette Club and I had my 81 Coupe, I replaced the water pump, but we had to sort through 3 pumps to find the right one and then I paid a premium price for it.
It too had a rear seal issue after a complete motor rebuild (yes I fixed that one and didn't break the main bearing cap bolts;LOL). The new engine also leaked from the bottom of the dizzy and the inlet manifold bolts...I pulled out one bolt at a time and sealed each one with high temp thread sealant.
I replaced the stock inlet manifold with an Edelbrock and topped it off with an Edelbrock QJet carb...the previous owner put a 600 Holley on there and as soon as I put the 780cfm QJet on, she came alive...airflow = it could breath better.

My brake calipers, brake hoses and steering pump arrived yesterday...the pile of new parts just keeps getting bigger, and due to the new house and the work around it, I get the death stare from the wife if I get side tracked and head towards the shed instead of doing the pool fencing...nah shes not that bad...:L...she told me to go work on the Vette a couple of weekends ago.

Appreciate the help.

Cheers, Tony
 
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AussieCorvetteNut

Well-known member
Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
...bolt is out

Bolt came out within 20 minutes, cleaned the thread.

So far I have reinstalled the rear bearing cap, oil pump, oil pan and filter.
I haven't topped the oil or put the starter motor back in, been too busy with pool fencing...:mad

Will get back to it this weekend.:beer
 

AussieCorvetteNut

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Joined
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Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
Fired her up today

Bolt came out within 20 minutes, cleaned the thread.

So far I have reinstalled the rear bearing cap, oil pump, oil pan and filter.
I haven't topped the oil or put the starter motor back in, been too busy with pool fencing...:mad

Will get back to it this weekend.:beer


Filled oil today and re-installed the starter motor.
Cranked her over, oil pressure is good and strong and after warm up sits around 350 to 360.
Coolant temp is ok and thermo fan comes on around 92 degrees Celsius.

I know the water pump is on its way out, so am planning to put a new one in.
The power steering pump also has leaks and I have a new one ready to go in.

My metallic type noise is back, but it isn't there when the engine is cold, it comes on gradually as it warms.
I don't think it is the flywheel cover as I did a bit of tidy up work with a mallet.

I thought it may be the water pump, but this noise seems to come from the rear of the block.

Any thoughts?

Its got me stumped.

Tony
 

Midnight 99

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Nov 10, 2013
Messages
122
Location
Jefferson City, MO
Corvette
2019 GS Ceramic Grey A8 Conv. & 1969 Camaro SS
Did you reinstall the clutch disc the right way? If not the springs will grind against the flywheel bolts when you engage or disengage the clutch. The disc snout can also rub on the throwout bearing.
 

AussieCorvetteNut

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Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
Thank you

Did you reinstall the clutch disc the right way? If not the springs will grind against the flywheel bolts when you engage or disengage the clutch. The disc snout can also rub on the throwout bearing.

Hi Midnight,

I thought it may be clutch/ flywheel related, I did not remove these when replacing the rear main seal though.
The clutch has recently been done by the previous owner, but the guy stuffed it up and it went back to a Corvette Mechanic on the Gold Coast to redo the work.

The sound isn't there when the engine is cold, it gets louder as it gets to operating temp. Oil pressure is good.
I am pretty sure it isn't engine related, it has a few issues...water pump, maybe a sticky hydraulic lifter or TBI noise.
I did notice when I pushed the clutch in and out, that some of this noise or maybe an additional noise from this area, did change as the clutch was in and out...it also has a chirping noise...yes I think that throw out bearing.

I thought maybe exhaust as it would also expand as it got hotter. The air pump lines are still connected, but the pump has been guttered.

The flywheel cover was a little battered, so I tidied it up and straightened it out.

If I had a spare $5000 for an engine rebuild, It would be out by now.
The gearbox (4+3) is already giving me the $hits.

No Richmond dealers here in OZ, they want to pass other gearboxes on, not interested in spending their $8000 on a new gearbox though.

I wish I had my 81 Coupe back...

:beer

Tony
 
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AussieCorvetteNut

Well-known member
Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
Could it be a pilot bearing???

Hi Midnight,

I thought it may be clutch/ flywheel related, I did not remove these when replacing the rear main seal though.
The clutch has recently been done by the previous owner, but the guy stuffed it up and it went back to a Corvette Mechanic on the Gold Coast to redo the work.

The sound isn't there when the engine is cold, it gets louder as it gets to operating temp. Oil pressure is good.
I am pretty sure it isn't engine related, it has a few issues...water pump, maybe a sticky hydraulic lifter or TBI noise.
I did notice when I pushed the clutch in and out, that some of this noise or maybe an additional noise from this area, did change as the clutch was in and out...it also has a chirping noise...yes I think that throw out bearing.

I thought maybe exhaust as it would also expand as it got hotter. The air pump lines are still connected, but the pump has been guttered.

The flywheel cover was a little battered, so I tidied it up and straightened it out.

If I had a spare $5000 for an engine rebuild, It would be out by now.
The gearbox (4+3) is already giving me the $hits.

No Richmond dealers here in OZ, they want to pass other gearboxes on, not interested in spending their $8000 on a new gearbox though.

I wish I had my 81 Coupe back...

:beer

Tony


Just wondering if my noise could be a pilot bearing????

As I said before, the noise is not there when the engine is cold, but gets gradually louder as the car warms up.

:beer
 

Midnight 99

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Nov 10, 2013
Messages
122
Location
Jefferson City, MO
Corvette
2019 GS Ceramic Grey A8 Conv. & 1969 Camaro SS
It still may be the throwout bearing. It is possible that even with the clutch engaged and pedal pressure released the throwout bearing is touching the pressure plate and continues to spin causing accelerated wear. It will put out a metallic squeal which will change when you depress the clutch pedal. That said, I would not rule out the pilot bearing.
 

AussieCorvetteNut

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Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
...starting to think the gearbox has to come out.

It still may be the throwout bearing. It is possible that even with the clutch engaged and pedal pressure released the throwout bearing is touching the pressure plate and continues to spin causing accelerated wear. It will put out a metallic squeal which will change when you depress the clutch pedal. That said, I would not rule out the pilot bearing.

I am starting organise for the gearbox to come out.

The previous owner had a clutch kit put in 12 months ago, but the receipt says nothing about a replaced pilot bearing/ bushing or throw out bearing, although it shoul have come with the kit.

The DNE is leaking gear oil anyway, the OD is also leaking a bit.
I have a list of fluid leaks I am working on, the first was the rear seal, I have powers steering pump and hoses, the water pump is on the way, the gearbox and the OD unit.
The Dana doesn't leak...crap I hope there's gear lube in there:L

Just trying to do the sums on rebuilding the 4+3 and crossing the fingers the OD unit will work or opt for the Richmond 6 speed. I can only find a couple of the big names in the USA to supply the transmission, they want too much $$$$.
I tried emailing Richmond directly, but no response.

:beer
 

AussieCorvetteNut

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Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
I think I found the problem.

It still may be the throwout bearing. It is possible that even with the clutch engaged and pedal pressure released the throwout bearing is touching the pressure plate and continues to spin causing accelerated wear. It will put out a metallic squeal which will change when you depress the clutch pedal. That said, I would not rule out the pilot bearing.


Started the Vette up this morning and took her for a quick strap up the road.
Could not get any gears....

Clutch and throw out bearing.

The last owner only did it last year...but the tech had a couple of goes at it.
The 4+3 needs a rebuild anyway, so it's time to pull it all out.
 

AussieCorvetteNut

Well-known member
Joined
Dec 19, 2010
Messages
188
Location
Gold Coast Australia
Corvette
1984 Two-tone Blue Coupe
Could it be the thrust surfaces?

Started the Vette up this morning and took her for a quick strap up the road.
Could not get any gears....

Clutch and throw out bearing.

The last owner only did it last year...but the tech had a couple of goes at it.
The 4+3 needs a rebuild anyway, so it's time to pull it all out.

I started the Vette on the weekend and it had clutch and I took her for a drive around the block.

My original sound is still there, but only when the engine gets to operating temperature.
I started to think about what I replaced, new rear seal, remove rear main and oil pump...just generally going back over what I had done...apart from over torquing the bolts!

My sound was there after round 1 reassembly and still there after round two.

I went back over the factory repair manual and the last instruction may have been the most important.
It says to install the end cap and torque the bolts to 10-12 in.ft, then tap the crank with a lead hammer rearward than forward to line up the thrust surfaces.
I am wondering if this is causing the thrust bearing to make the noise when it warms up?

Please help.....
 

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