Question

[fipp]

Hi everyone,
Recently installed my digipanel which I have had for a couple of years and finally got installed. Tonite we drove about an hour to eat and I noticed
that it ran yellow on engine temperature for almost the entire trip and back. Some interesting things: 1) alarm went off about 25 minutes into the
trip when coasting through a small town but quickly subsided when coach idled. 2) previous owner installed a stop cock to shut off what I call the
heater box under the hood as PO said it helped him cool the rig in summer. Since it was a rather cool evening I stopped and opened the stop cock
thinking that allowing heat would maybe cool the engine down but it did not. It seemed to run green when idling but once up to speed went to yellow. I
do have a guage that I believe is working but doesn't move and doesn't show hot at all. I am wondering if it is normal for the digipanel to show
yellow? My overflow tank is full. Just wondering if anyone can offer me any ideas. Thank you
--
Scott D. Fippinger
Aledo, Illinois
1976 Royale

 

[Jim Hupy]

Check the actual coolant temperature with a wireless digital temp reader
aimed at the thermostat housing and the top tank of the radiator. Perhaps
your digi panel is not accurately reporting the temp. They can fail just as
easily as anything else can. Always, always, verify that you actually do
have a problem before you try to fix it.
Jim Hupy
Salem, Oregon

On Tue, Apr 21, 2020, 7:32 PM Fipp via Gmclist
wrote:

> Hi everyone,
> Recently installed my digipanel which I have had for a couple of years and
> finally got installed. Tonite we drove about an hour to eat and I noticed
> that it ran yellow on engine temperature for almost the entire trip and
> back. Some interesting things: 1) alarm went off about 25 minutes into the
> trip when coasting through a small town but quickly subsided when coach
> idled. 2) previous owner installed a stop cock to shut off what I call the
> heater box under the hood as PO said it helped him cool the rig in
> summer. Since it was a rather cool evening I stopped and opened the stop
> cock
> thinking that allowing heat would maybe cool the engine down but it did
> not. It seemed to run green when idling but once up to speed went to
> yellow. I
> do have a guage that I believe is working but doesn't move and doesn't
> show hot at all. I am wondering if it is normal for the digipanel to show
> yellow? My overflow tank is full. Just wondering if anyone can offer me
> any ideas. Thank you
> --
> Scott D. Fippinger
> Aledo, Illinois
> 1976 Royale
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[bdub]

The yellow light indicates that the coolant temperature is running hotter
than normal. You should check for problems. Just because the catch can is
full doesn't necessarily mean it's working. Make sure the hoses are clear
and not stopped up. When cold, take the cap off the radiator to insure
that it is full.
Those digital temperature guns are very handy gadgets to double check
things. Very useful in several places on the GMC.
I looked at Applied GMC at the Digi-Panel instructions but was unable to
determine at what temperature the yellow light comes on. That would be
very good information to have. I expect around 210* or so.
On the OEM temperature gauge, normal is 1/4 way up the dial. At halfway
up, you're overheating. A common mod is to install a different temperature
sender so that it reads at the halfway mark at normal as we think it
should. It is NAPA #TS-6469. See here:
http://bdub.net/gmcmotorhome.info/engine.html

bdub

On Tue, Apr 21, 2020 at 9:32 PM Fipp via Gmclist
wrote:

> Hi everyone,
> Recently installed my digipanel whic I have had for a couple of years and
> finally got installed. Tonite we drove about an hour to eat and I noticed
> that it ran yellow on engine temperature for almost the entire trip and
> back. Some interesting things: 1) alarm went off about 25 minutes into the
> trip when coasting through a small town but quickly subsided when coach
> idled. 2) previous owner installed a stop cock to shut off what I call the
> heater box under the hood as PO said it helped him cool the rig in summer.
> Since it was a rather cool evening I stopped and opened the stop cock
> thinking that allowing heat would maybe cool the engine down but it did
> not. It seemed to run green when idling but once up to speed went to
> yellow. I do have a guage that I believe is working but doesn't move and
> doesn't show hot at all. I am wondering if it is normal for the digipanel
> to show yellow? My overflow tank is full. Just wondering if anyone can
> offer me any ideas. Thank you
>

 

[john r. lebetski]

I’d start by inspecting the cap. They have several fail modes. Very common is the invisible spring on the center return poppet valve fails. Then
coolant pumps out each time you get warm and no pressure in system. Constantly underfilled. You could have a stat that has failed in in a partly open
mode. This happened to me this year where the hoop came detached from the body and main spring went sideways. Since gone to Flowkooler 195. Very
accurate. Check overflow hose for cracks and porosity by flexing. This sucks air during cooling cycle and radiator is not full even though reservoir
looks good. Lastly inspect your fan clutch. There is extensive procedure in svc manual. Usually these vehicles do not overheat idling. Dissipating
road load heat is the challenge. Depending how the clutch has failed, of several ways, it might be transmitting power spinning fairly well at idle,
but not transmitting enough at demand. Or the bimetallic spring is gummed up and can’t turn valve properly. These I spray with WD-40 to act as a
flushing solvent, wait for it to dissolve gunk then spray again to wash it away. They all leak a bit of silicone and the tons of air going past it
attracts road dirt to the silicone oil till all spaces on coil are packed with dirt.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[gmcnet1]

How's your fan shroud? It's an important piece of the puzzle as well.
--
Christo Darsch
GMC Nor'easters
1977 Eleganza II - "The Komet"
3.50 Power Drive, Disc Brakes, Alcoas
Weymouth, MA