: 77 Deville engine knocking - New purchase



KiwiCady
09-28-11, 04:36 PM
Hi all!

I am stoked to be the proud new owner of a 77 coupe Deville.
I bought it in california and have just got it back to New Zealand.

It ran fine in the states but when we got it back in NZ it had leaked it's trans fluid in the container and we had to put in several litres to get it moving again.

Now when we fire it up it's got a loud knock that sounds like it's coming from the lower rear of the engine.
We've done an oil change and topped up the trans fluid.
When you start it from cold the knock is very quiet but gets louder as it warms up.

Does anyone have any suggestions as to what this might.
We removed the torque converter cover but this didn't really help to trace the problem.

Also it's a bi low on power and someone suggested the secondaires could be jammed closed, does anyone know the best way to free these up.

Thanks for your time, any help would be greatly appreciated.

Engine 7.0 425. Transmission 3 speed hydramatic

carnut
09-29-11, 03:32 PM
I would remove the bolts holding the flywheel to the t/converter and push the converter back into the bellhousing. Start the car and see if the noise is gone. Dont rev it up much, no load is on the engine! If gone, then the flywheel ( flex plate ) is cracked. If still there it could be carbon in the cylinders and a good top end engine cleaner might purge it. Hard to diagnose on the internet! Regarding the secondaries, With the air cleaner off to one side, engine off, open the throttle by hand a few inches, then press on the large secondary flaps. They should easily open and spring back closed. The actual secondaries are mechanical and always open, but if the flap is bound up, no air will go thru. I've seen the metering rods that are pulled up when this flap opens become stuck, which will bind up the flap. Spray either brake cleaner or carb cleaner around the passenger side of the carb, by the choke linkage as well as the shaft on the secondary air flaps. Report back.

carnut
09-29-11, 03:37 PM
Its common for the trans to leak from old seals on the dipstick tube and/or the pan gasket in long term storage. The torque converter drains back and overfills the transmission. They make a dye to add to the fluid that glows under a black light to pin point leaks.

deVille33
09-30-11, 09:08 AM
These engines have a tendency to to have pocket cavitation when sitting idle for a long time. How long did it take for the voyage from Cal. to Australia?
If this is the case, a good run down the highway will clear it up. It could also be carbon, as carnut suggested. The hotter the carbon gets, the the more preignition your engine will have and the louder the knock will be.
After you have your engine warmed up, check the oil at the dipstick. If you see any indication of metal in the oil, you may have a spun bearing. It would perhaps be a good idea to change the oil anyway. Then you can have it analyzed, and you can check it better. If you see a few small bits of metal, it could be regular operating results. A lot, then check your oil filter element for bigger particles.

csbuckn
09-30-11, 10:41 AM
Maybe put an oil pressure gauge on it and start it up, hopefully it doesnt get too low. The oil pump is external so you can pull it off and check it out also.

pompste
09-30-11, 11:03 PM
Hi all!

I am stoked to be the proud new owner of a 77 coupe Deville.
I bought it in california and have just got it back to New Zealand.

It ran fine in the states but when we got it back in NZ it had leaked it's trans fluid in the container and we had to put in several litres to get it moving again.

Now when we fire it up it's got a loud knock that sounds like it's coming from the lower rear of the engine.
We've done an oil change and topped up the trans fluid.
When you start it from cold the knock is very quiet but gets louder as it warms up.

Does anyone have any suggestions as to what this might.
We removed the torque converter cover but this didn't really help to trace the problem.

Also it's a bi low on power and someone suggested the secondaires could be jammed closed, does anyone know the best way to free these up.

Thanks for your time, any help would be greatly appreciated.

Engine 7.0 425. Transmission 3 speed hydramatic

What grade of gasoline are you running in it---regular,mid-grade, or premium? You said it ran good in the states but not in NZ.Any difference between USA gas and NZ gas? Just a thought.
My 7.0 425 knocks a bit running regular and mid-grade.No knocks at all when i run premium though.
It may also just need a good "wide open throttle" on the highway to clear out all the possible carbon buildup.These carbureted cars need good carb cleanings and "pedal to the floor"" highway runs every now and then.
Other poster`s here also have chimed in with great suggestions.

carnut
10-01-11, 12:19 AM
The wide open throttle idea mentioned here can be done in second gear as well. but please do this last! Once the oil pressure and flywheel diagnosis has been done. Wide open throttle in second keeps you at the speed limit but allows the engine to turn the same RPM as if the car was doing 90 MPH.

pompste
10-01-11, 04:53 AM
The wide open throttle idea mentioned here can be done in second gear as well. but please do this last! Once the oil pressure and flywheel diagnosis has been done. Wide open throttle in second keeps you at the speed limit but allows the engine to turn the same RPM as if the car was doing 90 MPH.

Thanks for having my back carnut! You`re right,the WOT should be done LAST.

deVille33
10-01-11, 11:55 AM
Maybe put an oil pressure gauge on it and start it up, hopefully it doesnt get too low. The oil pump is external so you can pull it off and check it out also.
There is a oil port plug above the pump on the right side of the block. This is your main galley port. Difficult to get to with the engine in the car, but doable. It takes either the square drive or a hex driver to remove it. It will be tight, so make sure the tool is set well into the plug, if you decide to do this.

KiwiCady
10-02-11, 02:38 AM
Thanks for the feedback guys.
We've separated the flywheel from torque converter and its eliminated the knock.
The engine runs perfectly, no noise what so ever.
The flywheel looks perfect, no cracks or tears.

Which I guess leaves the gear box or the torque converter.
Any suggestions as to where to from here?

Cheers

carnut
10-03-11, 02:13 PM
The cracks in the flywheel are around the small circle of bolts holding it to the crankshaft, hard to see except sometimes you can see rust streaks coming down away from the crack. I doubt the torque converter would cause a knock.

KiwiCady
10-05-11, 03:16 PM
Hi carnut, we had a good look at the flex plate with it removed from the torque converter and couldn't see anything. Are we best to drop the trans for a closer inspection?
Is there any parts of the trans that can be tested while it's still in place?

carnut
10-06-11, 02:34 PM
Nothing that I would think could cause a knocking noise. Was the inspection cover damaged at all? could you see all the bolts holding the flex plate on?

cadillac_al
10-07-11, 10:52 PM
I've never had a torque converter failure before but my old Chevy pickup has a terrible knock that really seems to be coming from the torque converter. I haven't had time to unbolt it. I hope it's only the flexplate but it really sounds like something rattling around in that tc. just some more food for thought.

KiwiCady
10-19-11, 05:13 AM
We think we've traced the problem to the engine. We've taken the sump off and found that the crank is hitting the block, due to too much end play. Does anyone know how to replace The thrust bearing and where's it located. Cheers

deVille33
10-20-11, 10:47 AM
I think the thrust bearing is #4 main jounal. I'll check the free block I have at one of my shops, but I'm sure I'm right. If you do have this problem, you are going to have to check the thrust surfaces of the crank, as I've found that such failure usually results in thrust surface damage. You don't say where you are from, but if you are nearby, I offer you my assistance in checking it out.

csbuckn
10-20-11, 11:09 AM
Number three main bearing in the middle, the one with the pickup tube on it.
The bearing on the right in the picture. After the new bearings, you'll have to find out what was causing so much pressure on the thrust bearing.
http://i935.photobucket.com/albums/ad196/csbuckn/_DSC0185-1.jpg

deVille33
10-20-11, 05:30 PM
Yes, I checked the free block and it is #3 main jounal. You can raise the engine and place blocks between the engine mounts and the frame mount to gain clearance and then you can remove the oil pan from underneath the car.

KiwiCady
10-25-11, 09:30 PM
Great thanks for that. We have now removed the engine, crank and gear box.
We've sent in the crank to get repaired. Hopefully welded up and grinded back down.

Now my next question is what was causing the crank to push forward. From what we can tell its had a new torque converter installed as the one we have is bright green and doesn't look 30 years old.
Does anyone have any suggestions on what it could be. We don't want to put the repaired crank back in, only to have it happen again. Cheers guys.

deVille33
10-26-11, 09:38 AM
Although I have seen this wear on several engines other than Cadillac, I can't suggest what may cause this other than dumping the trans into gear with the engine revving at high rpms or using the engine for racing using a high stall torque converter, which that green torque converter may be. Is the converter smaller in diameter than the standard TH400 torque converter? If so, it most likely is a high stall converter.
I would scutinize the engine further. While you have the crank out, check the main journal alignment. With the crank moving like that, there is a possiblity the webs have shifted. You may also want to check your cylinder walls wear patterns and the bores. That motion makes the pistons and rings reciprocate at an angle to the cylinder walls, and the resulting wear will affect cylinder sealing.
Just a heads up.