TAD valve?
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TAD valve?
'90 EFI 351
What is the air valve is behind the upper air intake manifold.
Its got a line coming in from the air pump, or rather air bypass valve, with a vacuum control line to control air to it seems exhaust manifolds on both sides.
My question is what is this, and does it connect to the exhaust manifolds. ?
The Haynes manual mentions a hose that goes to the catalytic convertor from the TAD. But nothing in there matches what I see on my truck
I noticed some smoke coming from the back in that area and the firewall behind is black from this. I know i have an upper exhaust problem somwhere but its hard to see until i take off the upper air intake manifold.
Im hoping somethings not connected right. I hope its not the exhaust manifold, but who knows.
What is the air valve is behind the upper air intake manifold.
Its got a line coming in from the air pump, or rather air bypass valve, with a vacuum control line to control air to it seems exhaust manifolds on both sides.
My question is what is this, and does it connect to the exhaust manifolds. ?
The Haynes manual mentions a hose that goes to the catalytic convertor from the TAD. But nothing in there matches what I see on my truck
I noticed some smoke coming from the back in that area and the firewall behind is black from this. I know i have an upper exhaust problem somwhere but its hard to see until i take off the upper air intake manifold.
Im hoping somethings not connected right. I hope its not the exhaust manifold, but who knows.
Lead Driver
Joined: Sep 2002
Posts: 9,182
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From: Gateway to the West
Most likely you have a bad exhaust check valve on the crossover tube that connects the air injection ports in the heads. Its a metal tube about 3/4" in diameter with a metal check valve somewhere just left of center as you are facing the front of the truck. They are known to break or snap in half. Without this check valve in place, the air injection is no longer pushing fresh air down the tube and hot exhaust can escape back through it. Its difficult to see as the tube connects at the rear of the heads and runs across the back of the engine very near the firewall. You will want to fix it soon however because the main engine bay wiring harness runs across the cowl/firewall just above the chack valve. (No, I've never had this happen before...and I've got a bridge in New York I wanna sell ya to).
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exhaust check valves
'90 EFO 351
I found out i have 2 exhaust check valves coming off the TAD(Thermactor air diverter). THeir behind the Upper intake manifold. I can see the one which goes into the exhaust manifold on the right (facing engine)and it seems fine, but the other ones a bit harder to see without taking off the Upper air intake manifold. (Thats the one with a lot of black smoke above it).I think that goes to the cat convertor then.
I found out i have 2 exhaust check valves coming off the TAD(Thermactor air diverter). THeir behind the Upper intake manifold. I can see the one which goes into the exhaust manifold on the right (facing engine)and it seems fine, but the other ones a bit harder to see without taking off the Upper air intake manifold. (Thats the one with a lot of black smoke above it).I think that goes to the cat convertor then.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
Yes, that is the one mounted in the crossover tube. Its a PITA to get to with the upper intake plenum in place. The other one is BELOW the diverter valve in the line. Being check valves they keep exhaust from coming back up the air injection hoses and tubing. They should be noted in the emissions diagram under the hood too.
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