Overheating in mountains

G

gene

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Sep 29, 1999
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cinnabar sells them, let me know how much they ask for them

Parts Department at 1-800-720-2227

gene

>Hi Guys,
>My own GMC is well and relaxing at home. My Dad's GMC overheated twice
>on our recent trip to the mountains. It was a long steep climb done
>about 25 mph in low gear. Probably 30 minutes of steady climb w/out down
>hill relief. He had a 7 psi cap(now a 10) and his needle went to the 1/2
>way point and was loosing coolant pretty soon. My GMC showed no signs
>of strain on same climb. We have since put a new Hayden 2797 fan
>clutch on it ,thinking the slow speeds with a dysfunctional clutch would
>have put little air thru the radiator. However, the old clutch passed
>the spin test. We have not been able to test this theory since there
>are no mountains nearby. His unit did not overheat again in 200 plus
>miles of driving after we got down out of mountains and cruised 60-70
>mph. We are thinking of replacing the radiator also since he doesn't
>want to be stranded again. Are there new radiators still being built and
>where can he find the best price ?? Otherwise we can have his unit
>recored. If we recore with modern core, is there any reason why he
>can't use a 15 psi cap ? Comments and suggestions hereby solicited !!
>
>Happy Trails to You,
>Hugh Fellows
>
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
Hi Guys,
My own GMC is well and relaxing at home. My Dad's GMC overheated twice
on our recent trip to the mountains. It was a long steep climb done
about 25 mph in low gear. Probably 30 minutes of steady climb w/out down
hill relief. He had a 7 psi cap(now a 10) and his needle went to the 1/2
way point and was loosing coolant pretty soon. My GMC showed no signs
of strain on same climb. We have since put a new Hayden 2797 fan
clutch on it ,thinking the slow speeds with a dysfunctional clutch would
have put little air thru the radiator. However, the old clutch passed
the spin test. We have not been able to test this theory since there
are no mountains nearby. His unit did not overheat again in 200 plus
miles of driving after we got down out of mountains and cruised 60-70
mph. We are thinking of replacing the radiator also since he doesn't
want to be stranded again. Are there new radiators still being built and
where can he find the best price ?? Otherwise we can have his unit
recored. If we recore with modern core, is there any reason why he
can't use a 15 psi cap ? Comments and suggestions hereby solicited !!

Happy Trails to You,
Hugh Fellows
 
Hugh,
There are several questions to ask. Is the radiator original? Is the
temp sender original or is it the newer NAPA sender?

The radiator is not available new in its original layout. You can find
one of similar size with the trany cooler but not the internal oil
cooler. As long as the side tanks of the unit are not leaking you can
have it recored my any competent radiator shop. You want to use the HD
truck 4 row replacement core with 13 fins per inch and have a fin-tube
density at least or equal to the original core. Be sure that the shop
understands what you want.

If you reached 1/2 on the temp indicator with the old original temp
sender you came real close to turning it to toast. 1/2 is 250 deg F
where as 1/2 on the new sender is only 215. You want the NAPA sender TS6469.

A 10# cap is available from most autoparts suppliers from Stant #10237
you can get a 9# cap from the GM part network AC Delco type RC32
part You can use higher rated caps, but he increased pressure
will cause the core to expand and contract causing leaking and failure.
If you need to use a higher rated cap then you have others problems that
you need to find and resolve.

J.R. Wright
GMC GreatLaker
77 Eleganza II
Michigan

>
> Hi Guys,
> My own GMC is well and relaxing at home. My Dad's GMC overheated twice
> on our recent trip to the mountains. It was a long steep climb done
> about 25 mph in low gear. Probably 30 minutes of steady climb w/out down
> hill relief. He had a 7 psi cap(now a 10) and his needle went to the 1/2
> way point and was loosing coolant pretty soon. My GMC showed no signs
> of strain on same climb. We have since put a new Hayden 2797 fan
> clutch on it ,thinking the slow speeds with a dysfunctional clutch would
> have put little air thru the radiator. However, the old clutch passed
> the spin test. We have not been able to test this theory since there
> are no mountains nearby. His unit did not overheat again in 200 plus
> miles of driving after we got down out of mountains and cruised 60-70
> mph. We are thinking of replacing the radiator also since he doesn't
> want to be stranded again. Are there new radiators still being built and
> where can he find the best price ?? Otherwise we can have his unit
> recored. If we recore with modern core, is there any reason why he
> can't use a 15 psi cap ? Comments and suggestions hereby solicited !!
>
> Happy Trails to You,
> Hugh Fellows
 
Hugh

The radiator is designed for a 7 lb cap. A 15 lb cap will cause the rad to
fail. My advice to you is to change your caps to 7. An old cap might not
be holding pressure.

Wayne Newland F9300 75 Palm Beach Columbia, Md

> Hi Guys,
> My own GMC is well and relaxing at home. My Dad's GMC overheated twice
> on our recent trip to the mountains. It was a long steep climb done
> about 25 mph in low gear. Probably 30 minutes of steady climb w/out down
> hill relief. He had a 7 psi cap(now a 10) and his needle went to the 1/2
> way point and was loosing coolant pretty soon. My GMC showed no signs
> of strain on same climb. We have since put a new Hayden 2797 fan
> clutch on it ,thinking the slow speeds with a dysfunctional clutch would
> have put little air thru the radiator. However, the old clutch passed
> the spin test. We have not been able to test this theory since there
> are no mountains nearby. His unit did not overheat again in 200 plus
> miles of driving after we got down out of mountains and cruised 60-70
> mph. We are thinking of replacing the radiator also since he doesn't
> want to be stranded again. Are there new radiators still being built and
> where can he find the best price ?? Otherwise we can have his unit
> recored. If we recore with modern core, is there any reason why he
> can't use a 15 psi cap ? Comments and suggestions hereby solicited !!
>
> Happy Trails to You,
> Hugh Fellows
 
Wayne, I was under the impression that the proper rad. cap was a 9# GM#
6410619. I just bought one last week at AC/DELCO parts supplier for $6.00
plus change
Bill

> Hugh
>
> The radiator is designed for a 7 lb cap. A 15 lb cap will cause the rad to
> fail. My advice to you is to change your caps to 7. An old cap might not
> be holding pressure.
>
> Wayne Newland F9300 75 Palm Beach Columbia, Md
>

>
> > Hi Guys,
> > My own GMC is well and relaxing at home. My Dad's GMC overheated twice
> > on our recent trip to the mountains. It was a long steep climb done
> > about 25 mph in low gear. Probably 30 minutes of steady climb w/out down
> > hill relief. He had a 7 psi cap(now a 10) and his needle went to the 1/2
> > way point and was loosing coolant pretty soon. My GMC showed no signs
> > of strain on same climb. We have since put a new Hayden 2797 fan
> > clutch on it ,thinking the slow speeds with a dysfunctional clutch would
> > have put little air thru the radiator. However, the old clutch passed
> > the spin test. We have not been able to test this theory since there
> > are no mountains nearby. His unit did not overheat again in 200 plus
> > miles of driving after we got down out of mountains and cruised 60-70
> > mph. We are thinking of replacing the radiator also since he doesn't
> > want to be stranded again. Are there new radiators still being built and
> > where can he find the best price ?? Otherwise we can have his unit
> > recored. If we recore with modern core, is there any reason why he
> > can't use a 15 psi cap ? Comments and suggestions hereby solicited !!
> >
> > Happy Trails to You,
> > Hugh Fellows
 
Wayne,
The Factory cap is a 9# cap as listed in the GMC maintenance manual on
page 6K-1, third paragraph.

J.R Wright

>
> Hugh
>
> The radiator is designed for a 7 lb cap. A 15 lb cap will cause the rad to
> fail. My advice to you is to change your caps to 7. An old cap might not
> be holding pressure.
>
> Wayne Newland F9300 75 Palm Beach Columbia, Md
>

>
> > Hi Guys,
> > My own GMC is well and relaxing at home. My Dad's GMC overheated twice
> > on our recent trip to the mountains. It was a long steep climb done
> > about 25 mph in low gear. Probably 30 minutes of steady climb w/out down
> > hill relief. He had a 7 psi cap(now a 10) and his needle went to the 1/2
> > way point and was loosing coolant pretty soon. My GMC showed no signs
> > of strain on same climb. We have since put a new Hayden 2797 fan
> > clutch on it ,thinking the slow speeds with a dysfunctional clutch would
> > have put little air thru the radiator. However, the old clutch passed
> > the spin test. We have not been able to test this theory since there
> > are no mountains nearby. His unit did not overheat again in 200 plus
> > miles of driving after we got down out of mountains and cruised 60-70
> > mph. We are thinking of replacing the radiator also since he doesn't
> > want to be stranded again. Are there new radiators still being built and
> > where can he find the best price ?? Otherwise we can have his unit
> > recored. If we recore with modern core, is there any reason why he
> > can't use a 15 psi cap ? Comments and suggestions hereby solicited !!
> >
> > Happy Trails to You,
> > Hugh Fellows
 
To all

I am sorry for not checking the book before I started writing.

Wayne

>
> 6410619. I just bought one last week at AC/DELCO parts supplier for $6.00
> plus change
> Bill >>
>
> Bill - The right cap is the 9# one. I am looking at the AC/Delco box and it
> shows RC32 with GM part number 6410619 which is what you referenced.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
 
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