zigzagrv
Nazareth, PA
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Joined: 08/12/2004
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A stuck heat riser is the problem. It is on the right mainifold and when the engine is cold,it is closed, forcing the exhaust and heat thru the left exhaust manifold to bring the engine up to temp quicker. If it does not open after a few minutes, you WILL have overheating problems. Best fix is to remove the heat riser completely.
Ron
2003 Gulf Stream Ultra Supreme 33'
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zuckerwar
Maryland
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Joined: 06/11/2005
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Thanks guys. I never knew about this heat riser valve. I'll look into it tomorrow and get back to you with the results!
1989 Shasta Roadmaster
36' Class A with tag axle
454 Chevy 7.4l
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427435
Rochester, Mn
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Joined: 11/12/2005
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zigzagrv wrote:A stuck heat riser is the problem. It is on the right mainifold and when the engine is cold,it is closed, forcing the exhaust and heat thru the left exhaust manifold to bring the engine up to temp quicker. If it does not open after a few minutes, you WILL have overheating problems. Best fix is to remove the heat riser completely.
This is not a good idea. I have a big block Chevy in a car and inadvertently put some intake manifold gaskets in, once, that had the heat riser openings plugged off. Car wouldn't run decent for 30 minutes while the mainfold slowly warmed up.
Keep the heat riser valve---just replace it or get it freed up.
Mark
2000 Itasca Suncruiser 35U on a Ford chassis
2003 Ford Explorer toad with US Gear brakes,
ReadyBrute tow bar, and Demco base plate.
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horizon451
Henderson, NV
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Joined: 02/19/2006
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Definitely put headers and glass packs on it as you will be amazed at the performance improvement. Had an 86 Encounter on a P-30 in a past lifetime.
'02 Itasca Horizon 36LD
'02 Jeep GC toad
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bingoldsby
Oregon State Parks - somewhere
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Joined: 10/22/2006
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I forgot to mention (above) along with all the other things I had done - I had a leak at a plug on one of the radiator tanks. It was a plug threaded into a hole that wasn't being used. The collar that the plug is threaded into was breaking at the solder. When I tried to tighten the plug, the whole thing fell out.
I had to remove the radiator. They recored the radiator and fixed that plug. I suppose that has been part of the relief I've had from overheating. But it's all a suite of fixes that really has made a difference.
By the way, I bought a set of Headman headers from SummitRacing.com. I suppose the jury is still out on these (in my case), but for $289.00 for ceramic coated headers, it seemed the right price, considering the age of my coach. The installation cost $634.00
Brian K7ZRZ
Campgrounding hosting - Oregon State Parks
1987 30' Holiday Rambler Class A
GL1800 Goldwing - Honda Scooter Mounted
2000 Silver Miata LS Toad
Picture taken at Salem, Oregon
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bill h
el segundo
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Joined: 08/02/2001
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427435 wrote:zigzagrv wrote:A stuck heat riser is the problem. It is on the right mainifold and when the engine is cold,it is closed, forcing the exhaust and heat thru the left exhaust manifold to bring the engine up to temp quicker. If it does not open after a few minutes, you WILL have overheating problems. Best fix is to remove the heat riser completely.
This is not a good idea. I have a big block Chevy in a car and inadvertently put some intake manifold gaskets in, once, that had the heat riser openings plugged off. Car wouldn't run decent for 30 minutes while the mainfold slowly warmed up.
Keep the heat riser valve---just replace it or get it freed up.
Certainly good advice for cold winters. If the RV is only a fair-weather vehicle, the heat riser is not as necessary. I drove a car with a wired-open heat riser for a year.
Bill and Susan
84 Barth 30 tag powered by ht502/Thorley, Gear Vendors OD
Siamese Calvin and Airedale Hobbes
4WD Toyota toad
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Daveinet
il
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Joined: 10/29/2003
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427435 wrote:zigzagrv wrote:A stuck heat riser is the problem. It is on the right mainifold and when the engine is cold,it is closed, forcing the exhaust and heat thru the left exhaust manifold to bring the engine up to temp quicker. If it does not open after a few minutes, you WILL have overheating problems. Best fix is to remove the heat riser completely.
This is not a good idea. I have a big block Chevy in a car and inadvertently put some intake manifold gaskets in, once, that had the heat riser openings plugged off. Car wouldn't run decent for 30 minutes while the manifold slowly warmed up.
Keep the heat riser valve---just replace it or get it freed up. I'm not sure but what this may be confusing. Getting rid of the heat riser valve means the exhaust flows freely from both manifolds which is not a problem. It seems like the problem 427435 would have had with closing off the manifolds is that there was no circulation through the manifold. Just because the heat riser valve is not there, there is still some circulation through the manifold - especially if you have an EGR.
I would suggest this - removing the heat riser valve is not going to be a problem in a motorhome. There is so much load on the engine, that it will warm up plenty quick enough. Anyone who installs headers has no heat riser valve and I've never had any issues traveling in the winter. Of course even now, I actually have the intake crossover locked off, and it still is not a problem, but I am running MPFI, so that may help.
Dave
FMCA F298817
'83 Revcon Prince 31' FWD
502 w/Thorley's & Magnaflows,
Howell/Edelbrock MPFI, Koni FSD,
Class A built for gear heads 
My Revcon Website
Revconeers Forum
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milazzo
bakersfield ca 93307
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Joined: 03/01/2004
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Many of the 454's had a vacuum chamber that operated the heat riser.
Look for a rod running from the heat riser valve to it. Could be stuck but may just have a vacuum line off or hooked up wrong. It should go to an intake manifold mounted valve which opens the heat riser after warm up..
Good luck
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bill h
el segundo
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Daveinet wrote: Anyone who installs headers has no heat riser valve.
I used Thorley's heat riser with my Thorley headers to be smog-legal.
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tropical36
Southwest Florida_USA
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Joined: 07/11/2004
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If you're disabling the dash ac, you may want to consider converting the condenser to a transmission oil cooler.
"We are often so caught up in our destination that we forget to appreciate the journey."
"It wasn't raining when Noah built the ark."
1998 36ft. National Tropi-Cal, with a tag axle and one slide, on a 1997 P32 Chevy chassis
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