Boil over.. no more...and other tid bits

[tim dawson]

Check the small vacuum host to see if it goes to a vacuum reserviour that is
about the size of an orange on the drivers side firewall. I suspect that this
is the vacuum source going to the heater/ac control head. If you are not
getting correct vent switching with this hose off, then you found it!

To repair, I bought a section of standard vacuum hose, since mine had adapters
on the ends (from GMC) to get the small stuff on a larger fitting. I just
went with the stuff that fit the fitting outright, and is more durable to boot.

- - Tim

> Thanks Emery I think I got the fluid vomiting under control.
>
> I installed the new radiator cap. I am not losing fluid any longer (at
> least I didn't on my test run). The cap I put on was a 10lb, that's all
> they had on hand at Napa.
>
> I also installed the new temp. sender.
>
> I noticed a couple of things while doing this.
>
> (1) there is a small black hose (maybe 1/8" diameter) that goes to a "T" on
> the intake manifold near the rear of the carb. This comes from somewhere
> near the front of the GMC? I initially thought this was a wire but I cut
> the melted end off and it is a small hose. Anyway, it had melted in half.
> Anyone know what this is and how to repair it.
>
> (2) A vacum line that runs from the front passenger side of the intake to
> the distributor (I assume to control timing advance) was cracked. I
> corrected this.
>
> (3) I do not think my fan clutch is working. I don't hear any roar at start
> up or when I am cruising up large hills? I need a replacement but there is
> no local Pep boys to purchase the Hayden 2797 HD. Napa does not have them.
> I'll check the other local stores but does anyone know where I could order
> one?
>
> Thanks in advance...
>
>
>
>
> >From: "Emery L. Stora"
> >Reply-To: gmcmotorhome
> >To: gmcmotorhome
> >Subject: Re: GMC: Boil over....
> >Date: Tue, 30 May 2000 16:11:24 -0600
> >
> >>Hey again,
> >>
> >>Last fall before we stored our GMC I flushed and filled the radiator
> >>with fresh fluid. I took it for a short drive after doing this and
> >>notices some fluid had been ejected from the system when I stopped.
> >>I didn't think much of it until yesterday. When I drove the GMC
> >>home from storage a noticed the "Engine Water" dash light. I added
> >>fluid when I got home and the light went out. Later we took another
> >>short trip (10-20 miles) and when we got home again some fluid was
> >>released from the system, I am guessing it was much less than a
> >>gallon. Later we went for another short trip (ice cream run) and
> >>the "Engine Water" dash light was lit again but it only stayed on
> >>for a few minutes?
> >>
> >>The temp gauge for the engine never got much more than a hair above 1/4.
> >>
> >>Any clues on this one. I am planning a new radiator cap but have
> >>not located one locally yet.
> >>
> >>Thanks in advance.
> >>
> >>Chris Taylor
> >>76 PB
> >>Rochester, MN
> >
> >Chris - first, pull out your original temperature sender unit
> >(located on front top drivers side of engine with a single wire
> >cliped to the top). The original sender showed 225 deg at 1/4 and
> >250 deg at 1/2. If it gets to 1/2 you are probably boiling out your
> >coolant. Go to NAPA and buy a TS6469 sender. This will show 1/4 at
> >180 deg and 1/2 at 215 deg. Apparently GM used the wrong sender.
> >Don't know their reasons but for years GMCers have been replacing the
> >original.
> >
> >It sounds as aif you definitely have a leak. You should borrow a
> >radiator pressure tester. I think that AutoZone has them in their
> >group of "loaner" tools. Fill your radiator, put the pressure tester
> >on and pump it up to the level shown for a 9 pound pressure cap.
> >Look at all hoses to make sure that none are dripping. Its not
> >uncommon to find a heater hose, radiator hose or even a small leak
> >from a radiator tube. A small drip will take a pressurized system
> >down a gallon in no time.
> >
> >If you were in NM instead of MN, I'd loan you my tester.
> >
> >Also use this tester to test your radiator cap. If it more than 1 to
> >2 years old it'll be bad and not hold pressure.
> >
> >Replace it with the original AC/Delco 9 pound cap. Check Gene
> >Fisher's site for the part number.
> >
> >Emery Stora
> >77 Kingsley
> >Santa Fe, NM
> >
> >Emery
>
> ________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
>
>

- --
================================================================================
Tim Dawson (tadawson) Owner/Engineer
TPC Services Bellnet: (972)-221-7385
Lewisville, Texas 75067 FAXnet: (972)-221-0393
"The world is complex. Sendmail.cf reflects this...."

 

[emerystora]

>I noticed a couple of things while doing this.
>
>(1) there is a small black hose (maybe 1/8" diameter) that goes to a
>"T" on the intake manifold near the rear of the carb. This comes
>from somewhere near the front of the GMC? I initially thought this
>was a wire but I cut the melted end off and it is a small hose.
>Anyway, it had melted in half. Anyone know what this is and how to
>repair it.
>
>(2) A vacum line that runs from the front passenger side of the
>intake to the distributor (I assume to control timing advance) was
>cracked. I corrected this.
>
>(3) I do not think my fan clutch is working. I don't hear any roar
>at start up or when I am cruising up large hills? I need a
>replacement but there is no local Pep boys to purchase the Hayden
>2797 HD. Napa does not have them. I'll check the other local
>stores but does anyone know where I could order one?
>
>Thanks in advance...
>

Chris -- the tube is a vacuum line that goes to the little black
plastic tank on the driver's side of the heater box under the
motorhome front access door. This gives vacuum to the vacuum servos
that operate the heater/ air conditioning doors. You can buy this
tube at auto parts stores. If you have a broken line just buy a
piece of 1/8" inside diameter rubber vacuum hose and push it over
both broken ends.

You should check your vacuum hoses frequently. I put new rubber
hoses on about every three years. the heat on the top of the engine
makes them brittle and they then to crack. I also suggest that you
put on new rubber "tees" and other connectors. I recently thought I
had a leak in my plastic tank but found that it was the little rubber
connector on the top that the 1/8" plastic tube fit into. My heater
controls work much better now that it is replaced.

Pep Boys only has three stores in Minn. Brooklyn Center, Coon
Rapids, and Inver Grove Heights. Any of them near you?

You could also call Master STC Inc. of Waite Park, MN. They are a
large dist. of Hayden clutches. 877-300-1234. Don't know if their
prices are any good though. Otherwise just call around to various
auto parts. Hayden has been in business for many years and a lot of
places stock their parts or can order them. My aux. tranny oil
cooler is a Hayden and I first put in on a 1969 Travco back in 1971.
Its still going strong on my GMC.

If you can't find one I can always go to the local Pep Boys and
purchase it and ups it to you. That might be faster than trying to
find one on the net.

Let me know.

Emery Stora
77 Kingsley
Santa Fe, NM

Emery Stora
77 Kingsley
Santa Fe, NM

 

[christopher taylor]

Emery, thanks again for the information.

What exactly does the small hose do? One thing I have noticed is that even
when my heater controls are on off air is still moving through the vents,
even when the coach is not moving.

The Pep Boys in MN are near the Twin Cities which is about 70 miles north of
here. I may just have to call them and take a trip to get the new fan
clutch. But thanks for your generous offer. If all else fails I might just
take you up on that.

Thanks again for all the great information.
I hope to have the fan clutch by this weekend.....

Chris Taylor
76 PB
Rochester, MN

Concerning the small tube
- ----- Original Message -----
From: Emery L. Stora
To:
Sent: Wednesday, May 31, 2000 4:25 PM
Subject: Re: GMC: Boil over.. no more...and other tid bits

> >I noticed a couple of things while doing this.
> >
> >(1) there is a small black hose (maybe 1/8" diameter) that goes to a
> >"T" on the intake manifold near the rear of the carb. This comes
> >from somewhere near the front of the GMC? I initially thought this
> >was a wire but I cut the melted end off and it is a small hose.
> >Anyway, it had melted in half. Anyone know what this is and how to
> >repair it.
> >
> >(2) A vacum line that runs from the front passenger side of the
> >intake to the distributor (I assume to control timing advance) was
> >cracked. I corrected this.
> >
> >(3) I do not think my fan clutch is working. I don't hear any roar
> >at start up or when I am cruising up large hills? I need a
> >replacement but there is no local Pep boys to purchase the Hayden
> >2797 HD. Napa does not have them. I'll check the other local
> >stores but does anyone know where I could order one?
> >
> >Thanks in advance...
> >
>
> Chris -- the tube is a vacuum line that goes to the little black
> plastic tank on the driver's side of the heater box under the
> motorhome front access door. This gives vacuum to the vacuum servos
> that operate the heater/ air conditioning doors. You can buy this
> tube at auto parts stores. If you have a broken line just buy a
> piece of 1/8" inside diameter rubber vacuum hose and push it over
> both broken ends.
>
> You should check your vacuum hoses frequently. I put new rubber
> hoses on about every three years. the heat on the top of the engine
> makes them brittle and they then to crack. I also suggest that you
> put on new rubber "tees" and other connectors. I recently thought I
> had a leak in my plastic tank but found that it was the little rubber
> connector on the top that the 1/8" plastic tube fit into. My heater
> controls work much better now that it is replaced.
>
> Pep Boys only has three stores in Minn. Brooklyn Center, Coon
> Rapids, and Inver Grove Heights. Any of them near you?
>
> You could also call Master STC Inc. of Waite Park, MN. They are a
> large dist. of Hayden clutches. 877-300-1234. Don't know if their
> prices are any good though. Otherwise just call around to various
> auto parts. Hayden has been in business for many years and a lot of
> places stock their parts or can order them. My aux. tranny oil
> cooler is a Hayden and I first put in on a 1969 Travco back in 1971.
> Its still going strong on my GMC.
>
> If you can't find one I can always go to the local Pep Boys and
> purchase it and ups it to you. That might be faster than trying to
> find one on the net.
>
> Let me know.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
>

 

[emerystora]

>
>
>What exactly does the small hose do? One thing I have noticed is that even
>when my heater controls are on off air is still moving through the vents,
>even when the coach is not moving.

That small 1/8" plastic hose provides all the vacuum for your heater/
air conditioning controls which open and close all the various doors,
etc. It leads to a small black plastic tank which is large enough
to provide all the vacuum needed providing that you have no leaks in
the system. There is a tube from that tank going up behind your dash
to provide vacuum for the rotary valve that actuates when you move
the "mode" lever from off to A/C to vent to heat, etc.

The reason that you still have air moving even when the control
switch is all the way down is because there is no "off" position on
the 76 or 77 models. The lowest position is "Low". GM, in its
infinite wisdom, decided in the mid 70 that all vehicles should have
some air flow all of the time. Many GMCers have disabled the low
position so that it is now a true "OFF". Go to Gene Fisher's site
http://www.california.com/~eagle/ and look under Heating and
Air Conditioning, Climate Control Fan Switch "off" modification.

Emery Stora
77 Kingsley
Santa Fe, NM

 

[gene]

Now would be a good time to move this connection to the booster side of
your electric vacuum booster pump. That way, you will have full vacuum on
your heater controls all the time. Often climbing a hill, the heater
controls stop working because the engine vac goes to almost zero.

gene

>>
>>
>>What exactly does the small hose do? One thing I have noticed is that even
>>when my heater controls are on off air is still moving through the vents,
>>even when the coach is not moving.
>
>That small 1/8" plastic hose provides all the vacuum for your heater/
>air conditioning controls which open and close all the various doors,
>etc. It leads to a small black plastic tank which is large enough
>to provide all the vacuum needed providing that you have no leaks in
>the system. There is a tube from that tank going up behind your dash
>to provide vacuum for the rotary valve that actuates when you move
>the "mode" lever from off to A/C to vent to heat, etc.
>
>The reason that you still have air moving even when the control
>switch is all the way down is because there is no "off" position on
>the 76 or 77 models. The lowest position is "Low". GM, in its
>infinite wisdom, decided in the mid 70 that all vehicles should have
>some air flow all of the time. Many GMCers have disabled the low
>position so that it is now a true "OFF". Go to Gene Fisher's site
> http://www.california.com/~eagle/ and look under Heating and
>Air Conditioning, Climate Control Fan Switch "off" modification.
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/

 

[emerystora]

>Now would be a good time to move this connection to the booster side of
>your electric vacuum booster pump. That way, you will have full vacuum on
>your heater controls all the time. Often climbing a hill, the heater
>controls stop working because the engine vac goes to almost zero.
>
>gene
>

Good point Gene. I did that when I put on my vacuum pump. If anyone
has gotten their vacuum pump from the junkyard you'll find that the
hose has a "T" fitting in it that is the exact size to fit the 1/8"
tube going to the plastic vacuum tank. My vacuum pump was coming on
about every 20 minutes so I assumed that I must have a leak
somewhere. I tested all the lines and couldn't find a leak. Took me
a long time but eventually I found the the rubber fitting on the top
of the vacuum tank that accepts the 1/8" hose was just old and was
not sealing properly to the tank. After replacing that rubber
fitting my vacuum pump now holds indefinitely.

Emery Stora
77 Kingsley
Santa Fe, NM

 

[bob mclaughlin]

Emery,
If memory serves me right(more questionable all the time) GM lost a lawsuit
or had some court ruling against them for carbon monoxide in one of their
vehicles. This was the late '50's or early '60's. Since that time all GM
manufactured vehicles have the blower on anytime the ignitions switch is on
as part of the settlement.
Bob McLaughlin

- -----Original Message-----
From: owner-gmcmotorhome
[mailtowner-gmcmotorhome]On Behalf Of Emery L. Stora
Sent: Thursday, June 01, 2000 8:12 AM
To: gmcmotorhome
Subject: Re: GMC: Boil over.. no more...and other tid bits