Where is vacume source for exhaust heat valve? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**ScottH** · 02-12-2009, 03:30 PM

Not sure if the term "heat valve" is correct but it is the part that is part of the exhaust manifold that closes during warm up and opens after (heat riser?). On the 84 305 I recently picked up there is no vacume line attached.

Also can anyone tell me without a vacume line does it stay in the open or closed position?

Any info is appreciated.

Thanks.

Scott

Longhorn321 · 02-12-2009, 03:34 PM

I'm sure if I'm wrong someone will correct me but IIRC, there is no vacuume line that goes to the heat riser. Heat just causes a bi-metallic strip to coil up and open the door.

OOOOPPS! I just looked and the heat riser is the thing between the exhaust manifold and the downpipe. I know what you are talking about tho on the air filter housing and I still say I think I remember the vacuume fitting does not actually get a vacuume hose fitted to it.

Longhorn321 · 02-12-2009, 03:42 PM

Looks like I was wrong.

Longhorn321 · 02-12-2009, 04:01 PM

Or did you really mean this...?? If so, I have never seen one like the one on the left so I am no help to you on that...Sorry.

**ScottH** · 02-12-2009, 04:24 PM

Yupper, that's it on the left.

Thanks for the info and for the pic, I'm sure it will help.

Scott

Longhorn321 · 02-12-2009, 06:36 PM

Well since I have never seen one like that, I can't give you any kind of real insight but I can take a stab at a guess... That thing would only be closed on a cold engine so the vacuume pot there would either have to apply vacuume to close it or apply vacuume to open it (my guess is vacuume to close so if it failed it would be open). Either way, there would have to be some vacuume switching device that switched when the temp changed. I would look for something that looks like a temp sensor screwed into the intake that has some vacuume fittings on it or a solenoid that has some vacuume fittings on it. I would guess that there would be two fittings, one would go to manifold vacuume and the other to the vacuume pot on the heat riser. <<<<<Lotta explanation for someone who has no idea what the truth is huh?

**ScottH** · 02-13-2009, 10:56 AM

Thanks Longhorn321

Anyone else?

ont_guy_38 · 02-13-2009, 11:21 AM

That valve is the EFE valve is this diagram

02-12-2009, 03:30 PM	#1
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Where is vacume source for exhaust heat valve? Not sure if the term "heat valve" is correct but it is the part that is part of the exhaust manifold that closes during warm up and opens after (heat riser?). On the 84 305 I recently picked up there is no vacume line attached. Also can anyone tell me without a vacume line does it stay in the open or closed position? Any info is appreciated. Thanks. Scott __________________ 1963 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon

02-12-2009, 03:34 PM	#2
Longhorn321 Size Matters Join Date: Aug 2007 Location: Lyman, SC Posts: 9,189	Re: Where is vacume source for exhaust heat valve? I'm sure if I'm wrong someone will correct me but IIRC, there is no vacuume line that goes to the heat riser. Heat just causes a bi-metallic strip to coil up and open the door. OOOOPPS! I just looked and the heat riser is the thing between the exhaust manifold and the downpipe. I know what you are talking about tho on the air filter housing and I still say I think I remember the vacuume fitting does not actually get a vacuume hose fitted to it. __________________ "Reading the owners manual is only for quitters." Jason Harper, Bloomberg News. ...WOOOO HOOOO!!!! Last edited by Longhorn321; 02-12-2009 at 03:37 PM.

02-12-2009, 03:42 PM	#3
Longhorn321 Size Matters Join Date: Aug 2007 Location: Lyman, SC Posts: 9,189	Re: Where is vacume source for exhaust heat valve? Looks like I was wrong. Attached Images __________________ "Reading the owners manual is only for quitters." Jason Harper, Bloomberg News. ...WOOOO HOOOO!!!!

02-12-2009, 04:01 PM	#4
Longhorn321 Size Matters Join Date: Aug 2007 Location: Lyman, SC Posts: 9,189	Re: Where is vacume source for exhaust heat valve? Or did you really mean this...?? If so, I have never seen one like the one on the left so I am no help to you on that...Sorry. Attached Images __________________ "Reading the owners manual is only for quitters." Jason Harper, Bloomberg News. ...WOOOO HOOOO!!!! Last edited by Longhorn321; 02-12-2009 at 04:02 PM.

02-12-2009, 04:24 PM	#5
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Re: Where is vacume source for exhaust heat valve? Yupper, that's it on the left. Thanks for the info and for the pic, I'm sure it will help. Scott __________________ 1963 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon

02-12-2009, 06:36 PM	#6
Longhorn321 Size Matters Join Date: Aug 2007 Location: Lyman, SC Posts: 9,189	Re: Where is vacume source for exhaust heat valve? Well since I have never seen one like that, I can't give you any kind of real insight but I can take a stab at a guess... That thing would only be closed on a cold engine so the vacuume pot there would either have to apply vacuume to close it or apply vacuume to open it (my guess is vacuume to close so if it failed it would be open). Either way, there would have to be some vacuume switching device that switched when the temp changed. I would look for something that looks like a temp sensor screwed into the intake that has some vacuume fittings on it or a solenoid that has some vacuume fittings on it. I would guess that there would be two fittings, one would go to manifold vacuume and the other to the vacuume pot on the heat riser. <<<<<Lotta explanation for someone who has no idea what the truth is huh? __________________ "Reading the owners manual is only for quitters." Jason Harper, Bloomberg News. ...WOOOO HOOOO!!!!

02-13-2009, 10:56 AM	#7
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Re: Where is vacume source for exhaust heat valve? Thanks Longhorn321 Anyone else? __________________ 1963 C10 swb fleetside 1966 GMC G1000 Handi-bus (future project) 1955 Chevy 2 dr. wagon

02-13-2009, 11:21 AM	#8
ont_guy_38 Registered User Join Date: Jul 2007 Location: Ontario Canada Posts: 1,006	Re: Where is vacume source for exhaust heat valve? That valve is the EFE valve is this diagram Attached Images



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