exhaust manifold leak at the heat riser bushings

runningdaddy

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After replacing my carb and dizzy, I finally got my 82 FJ40 (2F) up and running. Unfortunately, I found a leak in my exhaust manifold. Seems the manifold is leaking out the sides where the heat riser bushings pass from the inside to the outside.
Any ideas on how to repair or permanently seal (plug) these leaks without replacing the entire exhaust manifold? I'm pretty sure the original exhaust manifold is still on my ride.
For now, I'm in Hawaii and don't think I need to worry about cold weather for a while. I've already got a heat riser insulator installed and new Remflex gaskets installed.
 
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I usually rip out the heat riser valve and plug the two holes with a cutoff bolt and weld them with regular old mild steel mig wire (ER70-S). Haven't had one leak or fall out yet. We don't need the heat riser in central Texas either.
 

runningdaddy

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ImageUploadedByIH8MUD Forum1423590843.234207.jpg

I feel exhaust gas pressure at the center of the heat riser controller on both sides of the exhaust pipe.
 
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I had the same issue when I tore down to resurface and reseal the intake/exhaust. I pulled apart and drilled and tapped for a pipe plugs. I plugged with a brass plug and red loctite. I live in AZ so I dont moss the heat riser.
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I just wonder what exectly this heat raiser works?
Does it going to effect the performance of the engine if it's removed?
I believed mine is leaking from there too I can tell the exhaust gas marked on both sides and I don't see it can be fix unless remove the heat raiser ass'y out and plug them.
 

73FJ40

After another night of rust removal!
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The heat riser valve is located in the middle of the exhaust stream, with the intention that the valve directs the hot exhaust gas up to the bottom (outside) of the intake manifold to heat it up quickly, improving cold engine performance, allowing the choke to be opened sooner. The coil spring shown in the photo above heats up and turns the valve to be parallel with exhaust flow out the exhaust pipe, for normal hot operating condition.

It's likely frozen in the hot position and not functional. Honolulu HI is a no brainer to plug it up. California depends on your elevation (?)
 
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down in a hole.
the flap can be removed and new bushings pressed in...by a machinist...and as long as there isn't alot of below freezing driving to be done, the heat riser is not needed, and the flap can be removed and the holes plugged. below freezing, it should be considered a keeper- if it is working...
 
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My heat raiser is functioning but, seem to be stuck some time with the PO I torn my exhaust manifold apart to replace the manifold gasket and found that the heat raiser flap was torn, hole and mangle up on one side of the flap also the heat deflector was broken but not falling apart yet.
Install new Felpro gasket, heat raiser and heat deflector I put back on the way it was.
In California I don't think we need that heat raiser anyway.
 

spotcruiser

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I did one a while back. I removed the flapper and plugged the holes. Then I made a blank for the bottom of the intake manifold with 1/8" steel sheet. I made a blank for the EGR port also, since I was not going to use that either.

When people talk about removing the heat riser, doesn't that mean that hot exhaust gases will hit the bottom of the intake all the time? Won't that possibly crack the bottom of the intake?
 
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PabloCruise

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I did one a while back. I removed the flapper and plugged the holes. Then I made a blank for the bottom of the intake manifold with 1/8" steel sheet. I made a blank for the EGR port also, since I was not going to use that either.

Any problems with longer warm-up times?
 

spotcruiser

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Not really. It still has that direct mating between the cast iron exhaust manifold and the aluminum intake manifold, so the heat gets up there pretty quick. It can't be as instantaneous as the exhaust deflected up at the intake, but it's way better than the coolant method used with headers.

Any problems with longer warm-up times?
 

PabloCruise

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Not really. It still has that direct mating between the cast iron exhaust manifold and the aluminum intake manifold, so the heat gets up there pretty quick. It can't be as instantaneous as the exhaust deflected up at the intake, but it's way better than the coolant method used with headers.

Thanks! Did you tap the holes and screw in plugs? This seems like the most valid method to me, as I thought you could/should not weld cast materials?
 
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When people talk about removing the heat riser, doesn't that mean that hot exhaust gases will hit the bottom of the intake all the time? Won't that possibly crack the bottom of the intake?

Not really. Removing it is similar to having it open. When it's closed the hot gasses are pressurized a bit by the spring and forced to 'hang around' under the manifold for longer. When it's open, they head down the pipe, but the intake is still exposed to them in passing. SOR has a plate that insulates the intake further from the gasses and protects the intake more from cracking, but inhibits warm-up.

With the TR manifold (CA, '76-'78 only), the flapper causes the hot gasses to go around the inner casting and heat it to red-hot, which then acts to further burn the HC out of the exhaust, sort of like a catalytic converter, but cheaper at the time.

My '78 has a TR and the SOR plate. It does take longer to warm up. :meh: It also passes smog with a much higher threshold than my other 2f.

If I was removing the flapper setup, I'd tap and screw in plugs rather than weld. If I was going to weld, I'd have it brazed instead.
 

spotcruiser

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I actually made some plugs from 5/16" or 3/8" thick steel, a little tapered, and threaded them for a bolt. Then I bolted them in from the inside, cranked'em down tight, and welded the end of the bolts to the plugs. That way the manifold can be put back to original if desired.

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Thanks! Did you tap the holes and screw in plugs? This seems like the most valid method to me, as I thought you could/should not weld cast materials?
 

PabloCruise

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After replacing my carb and dizzy, I finally got my 82 FJ40 (2F) up and running. Unfortunately, I found a leak in my exhaust manifold. Seems the manifold is leaking out the sides where the heat riser bushings pass from the inside to the outside.
Any ideas on how to repair or permanently seal (plug) these leaks without replacing the entire exhaust manifold? I'm pretty sure the original exhaust manifold is still on my ride.
For now, I'm in Hawaii and don't think I need to worry about cold weather for a while. I've already got a heat riser insulator installed and new Remflex gaskets installed.

Are Remflex gaskets preferred when pulling the intake & exhaust?
 

roadstr6

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Are Remflex gaskets preferred when pulling the intake & exhaust?

Lay the assembled intake/exhaust manifolds on a table with the surfaces down and shine a light under to look for gaps. As long as your manifolds are totally flat the OEM, or Fel-Pro work fine. If gaps are minimal a Remflex gasket may get you by without machining. I had to have mine machined flat. I used the Fel-Pro with no issues.
 

spotcruiser

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I've used OEM and aftermarket gaskets. I really do like the Remflex gaskets. Just my opinion.
 

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