66 Fleetwood exhaust leak that sounds like it's coming from rear of engine

[scotth3886]

66 Fleetwood exhaust leak that sounds like it's coming from the back of the engine or intake.

Have a slight exhaust leak so we did all gaskets today.  Luckily manifolds bolts came out easily so nothing broken. 

Sound level of leak cut in about half, but it still sounds like there's a leak coming from rear of intake or valley pan or ??

I'm about to order more gaskets for intake and valley pan.  Any idea of what could be leaking back there? 

Not sure this makes a lot of sense as exhaust is on the other side of the heads. 

[Roger Zimmermann]

I'm not too familiar with the details from those years, but I assume that your car has a cross-over pipe in the intake manifold. If this channel has a crack, it makes the noise you are hearing.

[scotth3886]

I'm not too familiar with the details from those years, but I assume that your car has a cross-over pipe in the intake manifold. If this channel has a crack, it makes the noise you are hearing.

It has a cross-under pipe for the exhaust under the engine, but we checked all of that and replaced all gaskets yesterday so yes, it's got to be something to do with the intake.  This is my first experience with vintage Cadillac engines so I didn't know there was anything having to do with the exhaust in the intake. 

Wonder if this generally fixable or if I need to start scouting around for another intake?

[scotth3886]

Found something interesting that seems to describe what I'm hearing

http://6364cadillac.ning.com/forum/topics/inlet-manifold-429

[Roger Zimmermann]

Yes, of course, the tube for the choke is most probably broken/rusted away. This is a common issue.

[scotth3886]

I'm just going to replace intake.  Looks several good one on ebay for a price. 

Appears that everyone knows about the issue except me.  A little learning curve going on. 

Thanks for everyone's patience with me.

[gkhashem]

why would you replace the intake? Is it cracked?

You replace the tube in side of it.  Its a straight tube the pulls hot air up to the external tube you see at the choke thermostat spring. (same material, as the external tube)

[Roger Zimmermann]

I'm just going to replace intake.  Looks several good one on ebay for a price. 

But you don't know the condition of the tube! Mostly the sellers from those manifolds don't know the issue or dont want to remember it!

[Chuck Swanson]

Yes, of course, the tube for the choke is most probably broken/rusted away. This is a common issue.

I replaced my intake last year when I had my carb rebuilt as I had a spare intake blasted and painted on my shelf.  I did start to develop a tick last year.  The tube was partially crushed inside the intake.  I actually had to use a punch on the intake hole to get the new tube to carb piece to fit.  I started it up this year for first time and tick was gone.  However, a few minutes later, after warming up and tapping the gas pedal, it's back.  Could my partially crushed tube cause the tick?

As a side note, my exhaust manifold, gaskets, heat riser were all replaced around 5-6 years ago,  When I got this '65, heads were already rebuilt (who know when, but they were done and never had a tick until last) year.  Car also seem sluggish at times this year.   Thanks, Chuck

[scotth3886]

why would you replace the intake? Is it cracked?

You replace the tube in side of it.  Its a straight tube the pulls hot air up to the external tube you see at the choke thermostat spring. (same material, as the external tube)

External tube has been replaced by electric choke. 

This is a small Chebbie dealer I use to help with most anything that's going to be noisy.  I'm very grateful they let me bring the car to them and their one really ace mechanic.  Since it's a small new car dealer, what I can't do is tie up a service bay or lift for days while we're waiting for parts or machine shop or whatever.  I have to be prepared so if I have to have a spare intake on hand, then I have to do it.

I have to be careful here at home.  Can be a pretty intrusive HOA here and I don't want to get them started at me.  No one here is a old car fan and they think I'm nuts already.  I don't want to confirm it.  We're not even supposed to have our garage door open except for in and out.  Luckily, I have woods behind my house and the garage partially behind the house or I would be a world of problems by now.  It's a great place to live and don't want to be known as the problem. 

[scotth3886]

But you don't know the condition of the tube! Mostly the sellers from those manifolds don't know the issue or dont want to remember it!

If I'm buying a supposedly near 'perfect' intake, how can I tell its OK without it being on the car?   I don't mind buying another intake, but it isn't appealing to do this several times.

[gkhashem]

External tube has been replaced by electric choke. 

This is a small Chebbie dealer I use to help with most anything that's going to be noisy.  I'm very grateful they let me bring the car to them and their one really ace mechanic.  Since it's a small new car dealer, what I can't do is tie up a service bay or lift for days while we're waiting for parts or machine shop or whatever.  I have to be prepared so if I have to have a spare intake on hand, then I have to do it.

I have to be careful here at home.  Can be a pretty intrusive HOA here and I don't want to get them started at me.  No one here is a old car fan and they think I'm nuts already.  I don't want to confirm it.  We're not even supposed to have our garage door open except for in and out.  Luckily, I have woods behind my house and the garage partially behind the house or I would be a world of problems by now.  It's a great place to live and don't want to be known as the problem.

If that's the case then I think you can block off the internal tube, since you have an electric choke.

[35-709]

If that's the case then I think you can block off the internal tube, since you have an electric choke.

Right!
Just in case, I will add ----- 
- Very often the location of an exhaust leak is where the intake manifold crossover mates with the exhaust manifold, the gasket is usually blown out --- first on the side of the heat riser valve which I think is on the passenger side on the 429, then later on the left or exit side if the right isn't repaired.  This is caused by the heat riser valve sticking/rusting shut so that hot exhaust gases are passing through that area at all times instead of just when the engine is warming up --- it was not designed, nor intended to have, that kind of constant high heat and pressure.  That passage is at the middle of the exhaust manifold/intake manifold and goes under the carburetor.  Have to assume your heat riser valve has been removed or is wired open since you have an electric choke --- make sure that is the case.
If there is an exhaust leak there and it is not repaired (new gasket - heat riser made to work, removed, or blocked open), the continuous hot exhaust gases will ultimately erode the contact surfaces to the point that even a new gasket will not prevent a leak from coming back, immediately or soon, without machine work being done (planing the surface).


 

[scotth3886]

Right!
Just in case, I will add ----- 
- Very often the location of an exhaust leak is where the intake manifold crossover mates with the exhaust manifold, the gasket is usually blown out --- first on the side of the heat riser valve which I think is on the passenger side on the 429, then later on the left or exit side if the right isn't repaired.  This is caused by the heat riser valve sticking/rusting shut so that hot exhaust gases are passing through that area at all times instead of just when the engine is warming up --- it was not designed, nor intended to have, that kind of constant high heat and pressure.  That passage is at the middle of the exhaust manifold/intake manifold and goes under the carburetor.  Have to assume your heat riser valve has been removed or is wired open since you have an electric choke --- make sure that is the case.
If there is an exhaust leak there and it is not repaired (new gasket - heat riser made to work, removed, or blocked open), the continuous hot exhaust gases will ultimately erode the contact surfaces to the point that even a new gasket will not prevent a leak from coming back, immediately or soon, without machine work being done (planing the surface). 

All good reasons why I will have a 'spare' intake here before he starts on it.  It's cheaper than the labor to put it all back together and later take it apart again.  In once and done. 

[scotth3886]

I bought this

https://www.ebay.com/itm/1963-1964-1965-1966-Cadillac-390-429-Intake-Manifold-Refurbished-ONLY-ONE-LEFT/153840596122?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Hopefully, no issues.  I think cheaper in the long run too. 

[Chuck Swanson]

Good luck.  Can't believe these are going for $550.  I have one in that condition, and 12 more I need to clean up and have checked at my friends machine shop...I better get moving  

Please let us know how it works out, as my '65 Eldo  I believe has the same issue.  Chuck

["Cadillac Kid" Greg Surfas 15364]

Well while you are trying all the other things suggested above you might just check and see if the insulator betwee your carb and the intake hasn't deteriorated.  This is a common problem since they were made of "space age materials" of the 50's  (Bakelite)
Greg Surfas

[chrisntam]

It's purdy!

[scotth3886]

Well while you are trying all the other things suggested above you might just check and see if the insulator betwee your carb and the intake hasn't deteriorated.  This is a common problem since they were made of "space age materials" of the 50's  (Bakelite)
Greg Surfas

Thanks.  That will get addressed too.  I don't like paying labor for the same thing twice or doing the same thing over myself. 

[scotth3886]

It's purdy!

Thanks.  It was the most expensive one on ebay, but in the long run, the cheapest.  The one that's on the car now is pretty nasty looking so I would have had to media blast that one, fix whatever issues it has, etc., and all the while, tying his lift up.  If I do that a few times, I'm sure they will tell me that hey, they're a new car dealer and they can't tie their best mechanic and stall or lift up with my projects.  Goodbye.

And what I'm doing at home is a clear violation of HOA rules so that can lead to big issues too.