News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

472 Exhaust Manifold Leak

Started by Coupe Deville, April 28, 2014, 01:07:50 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Coupe Deville

Hello everyone. My 72 CDV has had a exhaust leak at the drivers side manifold ever since I have had it. The car only has 15,000 miles and was in storage for 20 years so I presume the manifolds have never been removed. I know they did not have gaskets between them from the factory. My main question is when I remove the manifold can I get it milled? Or just put gaskets in it? The manifold its self is actually in very good condition, no cracks, etc. I know these are a pain to pull with the stuck bolts too. Any tips for freeing them up and removing the bolts also?

-Gavin
-Gavin Myers CLC Member #27431
"The 59' Cadillac says more about America than a whole trunk full of history books, It was the American Dream"

"Cadillac Kid" Greg Surfas 15364

Gavin,
If the manifold is not cracked and the bolts are tight and it is leaking around one or more of the exhaust ports, the simplest way of correcting this (assuming the leak is not large enough to consider the manifold too warped to use) is to remove the manifold and use a gasket when re-installing it.
That's the good news.  I am sure you will get a lot of suggestions on removing the bolts, but I have never been able to remove all the exhaust manifold bolts (originals 30+ years old) without breaking at least one.  Perhaps I can learn something too.  When you do re install the manifold I would strongly suggest using grade * stainless steel bolts and non-seize compound.  I have been able to remove these decades after they have benn installed with no breakage.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

mgbeda

I was able to get all the manifold bolts off intact on my '76 DeVille with two tricks.  1) Use the "miracle" homebrew penetrant: a 50/50 mix of ATF and acetone (caution: flammable and strips paint immediately). 2) Use a box wrench and a hammer to loosen the bolts instead of using brute force or lots of leverage.  The impacts tend to break them loose without putting as much strain on the bolt.

Half the manifold bolts are accessible from the back as well as the front (i.e. they are screwed into through holes, not blind holes).  Be sure to soak these bolts at both ends.  And soak all of them for a few days before you try removing them.

I was asking he same question about gasket vs. planing a while back, and got opinions on both sides.  I decided to go with gaskets.  I'd especially do it on your car because that way you don't have to dismantle the other end of the manifold. You can just detach it from the engine, slip the gasket in, and reattach it.  Cheaper easier, and might work even better.

-mB
-Mike Beda
CLC #24610
1976 Sedan DeVille (Bessie)

Scot Minesinger

On the Y-pipe to manifold connections heat alone usually does it for me but not always.  The miracle 50/50 ATF/Acetone soaking from both sides (possible on three of the studs I think) followed by a couple days to wait will do the trick.  If you are not used to applying just enough torque to not break the studs, soak them first.  Yes, that hammer trick works very well too.

As Greg suggested replace the exhaust manifold to head bolts, and replace the studs connecting to Y pipe too (usually with slightly longer versions because the Y pipe flanges often are different and require the longer studs to install).
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Jeff Rosansky CLC #28373

Believe it or not, the exhaust manifold bolts are metric........ Really.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Scot Minesinger

Jeff,

I know why you would say that.  They deteriorate and get down to metric sizes.  On the exhaust manifold bolts they are 1/2" heads with 3/8" threads (at least in 1970), but after deterioration sometimes you have to use a metric to avoid stripping the head.  A 12mm is equal to 0.472 inches (1/2" is equal to 12.7mm).  If they are 9/16" in 1972, you may have to use a 14mm.  I had to use a 18mm on the head bolts down near exhaust instead of 3/4 to avoid stripping heads of the bolts. 

You make a good point, if the heads of the bolts are deteriorated and the socket may slip and strip head of bolt, use a smaller metric size (you may have to hammer it on with light taps) to avoid this problem.     
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Thule

there is a company makin new manifolds for the left side, they are on ebay for arund 200$

mine leaks to, on both manifolds, seem like i need at least 6 bolts
Ivar Markusson.  icelandic cadillac club (part of CLC)
73 Eldorado coupe.

Scot Minesinger

Once the exhaust manifolds are removed, the rest is gravy.  Replace all 8 (not six) bolts on each side as Greg suggested. 

You may think that you are never going to take them off again, but I had to when the head had to come off for a valve repair.  Mine was an engine in the car job, and although I could have removed the exhaust manifold and head as a unit, that makes it heavy.  It is not too heavy to remove, but it is very difficult to set back in place carefully enough to not damage the gasket, best to separate and manage with less weight.

Get the copper gaskets (set of 8 is like $39) and be done with that issue for a long time.

On the manifold replacements be careful of re-productions, I would rather go with good used.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Coupe Deville

Thank you everyone for the advice and tips. I will soak the bolts for a few days prior to removal. It wont happen until probbly next week thought due to other commitments. I was thinking about this. My friend owns a machine shop so I could probbly get the manifold machined for cheap. And then put the copper gaskets on. I think that is the best idea because the manifold will be true and it will have gaskets. How does that sound?
-Gavin Myers CLC Member #27431
"The 59' Cadillac says more about America than a whole trunk full of history books, It was the American Dream"

Scot Minesinger

You can machine the exhaust manifolds down too much - be careful.  I would put the manifold on a flat surface (table saw) and see for yourself, may not need to machine them.  The gaskets will pick up a small amount of slack.

Sounds like you have a good plan!
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Gene Beaird

Gavin, if your friend has a large table belt sander, that will work perfectly for this project.  I fixed a pair of warped Pontiac 455HO manifolds (they use only 3 bolts per side!) well enough I didn't have to use gaskets with a large belt sander.  You just want to take enough off to make it perfectly flat.  I guess a turret lathe or end mill might do the job, too, but the belt sander was quick and easy. 



Gene Beaird,
1968 Calais
1979 Seville
Pearland, Texas
CLC Member No. 29873

Scot Minesinger

The nice thing about the belt sander is it is the least aggressive on removing too much material - great suggestion.  Hopefully you will need to machine it.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

76eldo

You can also use a piece of glass as a flat surface to test or a metal straightedge and some feeler gauges.
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado