Heat Riser - The 1947 - Present Chevrolet & GMC Truck Message Board Network

85Silverado · 12-10-2002, 12:35 PM

Does anyone know if the Heat Riser (valve in passenger side exhaust manifold near flange) sticks closed or open when the vacuum line to it is disconnected or in my case gone? Thanks for any info

J-Spec C10 · 12-10-2002, 12:42 PM

In my truck, it was gone too. I had an exhaust shop check it and weld it in the open position. As for the position it stays, it kinda flaps around a bit.

IMO when the vacuum is applied the diaphragm should pull up on the rod right? So up should be open.

Good Luck!

85Silverado · 12-10-2002, 12:47 PM

Mine feels like theres some spring tension. I went out to move it and it went back to wide open or closed. Could that just be the vacuum diaphragm giving the tension?

**swervin ervin** · 12-10-2002, 12:49 PM

The valve opens with with a built in spring. When the engine is cold, vacuum which is routed throught the TVS closes the valve. As the engine coolant warms up, it slowly shuts off vacuum going to the valve, allowing it to open with the spring pressure.

So, if you have no vacuum going to it, it should be open all the time.

J-Spec C10 · 12-10-2002, 12:55 PM

theres the difference, I had no rod on mine, and the spring was broken.... the flapping noise drove me crazy!

85Silverado · 12-10-2002, 12:57 PM

Nuts, I was hoping it was closed. That pretty much means the weird noise coming from over there is more then likely a knock then.

12-10-2002, 12:35 PM	#1
85Silverado Registered User Join Date: Dec 2002 Location: Milwaukee, Wisconsin Posts: 198	Heat Riser Does anyone know if the Heat Riser (valve in passenger side exhaust manifold near flange) sticks closed or open when the vacuum line to it is disconnected or in my case gone? Thanks for any info

12-10-2002, 12:42 PM	#2
J-Spec C10 Whats this wire for?.... Join Date: Dec 2002 Location: Barrie, Ontario, CANADA Posts: 378	In my truck, it was gone too. I had an exhaust shop check it and weld it in the open position. As for the position it stays, it kinda flaps around a bit. IMO when the vacuum is applied the diaphragm should pull up on the rod right? So up should be open. Good Luck! __________________ Kyle CANADIAN CONNECTION '82 C10 Resto-Custom--> * 2 1/4" manifold back dual exhaust with Hooker Aerochambers & High Flow Cats Taylor Ignition Wires Centerline 15" Telstars with 32"x10" mudders

12-10-2002, 12:47 PM	#3
85Silverado Registered User Join Date: Dec 2002 Location: Milwaukee, Wisconsin Posts: 198	Mine feels like theres some spring tension. I went out to move it and it went back to wide open or closed. Could that just be the vacuum diaphragm giving the tension? __________________ Paul D. '78 C20 Scottsdale 350ci 3 speed with granny gear 14 bolt rearend My trucks are "Car-Guy safe".......which pretty much means death trap in the hands of a normal civilian.

12-10-2002, 12:49 PM	#4
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	The valve opens with with a built in spring. When the engine is cold, vacuum which is routed throught the TVS closes the valve. As the engine coolant warms up, it slowly shuts off vacuum going to the valve, allowing it to open with the spring pressure. So, if you have no vacuum going to it, it should be open all the time. __________________ Mike 1985 Chevy C-10

12-10-2002, 12:55 PM	#5
J-Spec C10 Whats this wire for?.... Join Date: Dec 2002 Location: Barrie, Ontario, CANADA Posts: 378	theres the difference, I had no rod on mine, and the spring was broken.... the flapping noise drove me crazy! __________________ Kyle CANADIAN CONNECTION '82 C10 Resto-Custom--> * 2 1/4" manifold back dual exhaust with Hooker Aerochambers & High Flow Cats Taylor Ignition Wires Centerline 15" Telstars with 32"x10" mudders

12-10-2002, 12:57 PM	#6
85Silverado Registered User Join Date: Dec 2002 Location: Milwaukee, Wisconsin Posts: 198	Nuts, I was hoping it was closed. That pretty much means the weird noise coming from over there is more then likely a knock then. __________________ Paul D. '78 C20 Scottsdale 350ci 3 speed with granny gear 14 bolt rearend My trucks are "Car-Guy safe".......which pretty much means death trap in the hands of a normal civilian.



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