leaky flange at y pipe

leaky flange at y pipe

Postby Coaster [OP] » April 24th 2017, 7:47pm

for a while now i have had leaks where the y pipe bolts to the exhaust manifolds. yesterday i went under there and got all 6 nuts to turn about 1/8 of a turn tighter. this surprised me that they turned, in any case with some work i can get them off given enough time and patience. they are not permawelded like i had assumed.

so i did tighten them within reason, the leak sound did improve but its not completely leak free. i dont think i have any donuts in there either, it seems metal to metal like my 1970 was. i dont know if i should buy a new y pipe and start over or attempt to get my existing flanges to seal. i have read TSB's for different years with similar setups rebending the flanges but i dont know.

this leak is really driving me crazy
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Re: leaky flange at y pipe

Postby AstroWill » April 24th 2017, 8:10pm

You got lucky on the nuts. The gaskets must have blown out, going to have to replace those, do both at the same time, as usually when one is gone, the other gets extra worn from the increased movement. How bad are the flanges, I have had some that were slightly beat up, just had to beat them back into the proper shape, worked just fine.
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Re: leaky flange at y pipe

Postby dramey » April 24th 2017, 8:17pm

Replace all 6 nuts with brass exhaust nuts while you are changing the donuts. That helps eliminate the permaweld.
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Re: leaky flange at y pipe

Postby Coaster [OP] » April 24th 2017, 10:58pm

i'll have to drop the y pipe and see whats in there. i've had issues like this on every 20+yo engine i have ever had. the 1970 350 got headers to fix it. the 69 318 got new flanges and newer manifolds off a 78.

69 still runs
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Re: leaky flange at y pipe

Postby 97cargocrawler » April 25th 2017, 9:25am

You should have 2 donut gaskets in there. Don't snug down the nuts down too much with the new gaskets, they will crush and fall apart. There's probably a torque spec for that someplace.
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Re: leaky flange at y pipe

Postby Coaster [OP] » April 30th 2017, 10:49pm

P82A22941.jpg

P82A22951.jpg


got them apart. no donut in there. took the y pipe down, scraped the black crud off and put it back. significant improvement although not sure why.
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Re: leaky flange at y pipe

Postby Coaster [OP] » May 5th 2017, 9:40pm

6 days of driving and i checked my BLM. it idles at 126 to 132!! prior to this it idled at BLM of 142 to 148. i have never seen it below 138 before

off idle it goes to 138 but at cruise it goes back down to around 131. look at all that black S*** in my manifolds in the above pic, 22 years of running rich. i have some downstream leaks in the pipe past the cat that i can see from one weld, i need to grind that clean and weld it better.

its actually running pretty well
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Re: leaky flange at y pipe

Postby Coaster [OP] » May 18th 2017, 1:23am

two weeks and i started to hear the leak again, and started to miss at idle. not as bad as before but still. i went under there after work today and the drivers side was TIGHT. the passenger side was loose, i was able to tighten the nuts up 1/4 turn or a little more. improvement on the ride home, but hmmm.

i may have to take the manifolds out, see if the need milled or not. i have had mixed results with milling manifolds. on mopars it works but gm's not so sure.

i probably could use a new y pipe too. but i think my 22 year old shot motor mounts from dairy queen soft serve may be working the exhaust loose.

i bought new poly mounts from rock auto. they are RED (flame suit on) :D
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Re: leaky flange at y pipe

Postby 97cargocrawler » May 19th 2017, 9:19am

The manifold should not have that lip, I believe what you have there is the rusted out internals of the donut stuck inside the manifold. The mushy lead outer ring is gone. I think if you PB Blast that rust and give the lip a tug that crap should come out.

I don't have a pic of my van, but here is the same type of Y pipe connection to the manifold in my truck:

Image

The gray lead section mushes to make the seal. There is a steel ring inside the lead to hold the shape and inserts snugly into the manifold.

EDIT: I found a pic that shows the donut on my van, left side..

Image

You can see the lip is much thicker because it has the lead gasket material intact.
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Re: leaky flange at y pipe

Postby Coaster [OP] » May 19th 2017, 1:01pm

here are some pics of the 95 manifold from rock auto. they are different from yours, which are as you describe. i also have no springs

674-385-001__ra_p.jpg
674-385-001__ra_p.jpg (38.14 KiB) Viewed 2518 times

674-385-002__ra_p.jpg
674-385-002__ra_p.jpg (21.15 KiB) Viewed 2518 times


i wish it was as easy as replacing a donut. napa lists one for 95, so does rock auto but both also list rocker arm types that dont work on a 95 :think:
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Re: leaky flange at y pipe

Postby 97cargocrawler » May 19th 2017, 2:20pm

I dont have springs either. Looks like the donut is installed in those manifold pix. Ok, I give up. Crawlin back into my hole :mrgreen:
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Re: leaky flange at y pipe

Postby Coaster [OP] » May 20th 2017, 2:33am

P82A23411.jpg


wish me luck
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