CUTLASS 307 y code olds intake manifold coolant leak

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jim83

Apprentice
Mar 21, 2018
60
8
What have you guys done to overcome the bad design on the front of the drivers side intake manifold? Hard to believe that the gm "engineers " didn't cast the head & manifold with a provison for a bolt at the end. More gm excellence- is there any that don't leak eventually? I put the manifold on exactilly per wsm using gm sealer- fine for a while, now seeping. Thanks for you ideas
 

DoubleV

Royal Smart Person
Feb 25, 2011
2,147
83
Medina Ohio
There's nothing wrong with the bolt arrangment. It's probably due to corroded aluminum around the coolant port.....or you didn't do it right!
 
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Texas82GP

Just-a-worm
Apr 3, 2015
7,730
113
Spring, Texas
Back in the mid 90's I had to contend with a badly corroded aluminum intake on a 307. My initial plan was just to replace it with a better intake. I went to several yards and couldn't find one better than what I had so I repaired mine. I used a wire wheel to deep clean the pits around the water passages. Then I filled the pits with JB Weld. Then I carefully 'machined' all four corners where I filled with JB weld by sanding both machined surfaces of the manifold with a long (roughly a foot) sanding block. I think I started with 180 or 220 grit sand paper. When I went back together I used aerosol coppercoat around all the intake ports on both sides of the new valley pan. Then I used RTV on both sides around the water passeges. It was a good repair. It held up well. Keeping your coolant at minimum 50% concentration and keeping it changed on those engines is critical. Too many dissimilar metals. Iron block and heads, aluminum intake, stamped steel valley pan. I'm not a big fan of the 307 over that valley pan and the rocker 'bridges'.
 
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Oct 14, 2008
8,323
113
Melville,Saskatchewan
The A4 is actually rare up here and almost all the 307's in Canada had the #17 iron intake. The swirl port ones did receive the A5 but only failed occasionally. No issues after 400,000 km with the iron intake. I never had issues with an aluminum intake sealing with the Turkey tray with RTV black around BOTH sides of the the tray and tall beads at both ends instead of the rubber end seals. Thermostat sealing has been an issue, with either the factory aluminum or polished RobbMc water neck. I need 2 to 4 gaskets with layers of RTV black or The Right Stuff.
 
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jim83

Apprentice
Thread starter
Mar 21, 2018
60
8
I'll try the rtv, I used the genuine gm gasket sealer 1050026 per wsm & it didn't hold. Manifold & head were checked for straight.
You can't convince me it's a good design, coolant goes across it & only 1 bolt??? Following that logic, the thermostat housing would be fine with only 1 bolt also...
 
Oct 14, 2008
8,323
113
Melville,Saskatchewan
Not saying it is the best design but it works OK, how you seal it makes a huge difference.
 

spidereyes455

G-Body Guru
Mar 6, 2013
717
93
Northeastern PA
+1 on the corroded intake port. It was such a common problem when these cars were DD's that one garage I worked at 20 some years ago would automatically call the junkyard and have them send us a cast iron intake every time an Olds v8 came in with a leaking intake gasket. Why? Cause the iron ones never leak.
 
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