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11-29-2007, 09:08 AM
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#1
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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This one is huge..and, of course you have to be out-of-warranty and it will make your rig run
a little dirtier, smog-wise--maybe..
But can you imagine the benefits of running 15*
F. cooler???
There are a ton of them (reasons). There's another parameter,
I was told,--dunno--when the ECM
starts to pull power (timing) out of the
OBD2's timing tables and it is related to
coolant temperature. At 212* F. (or 100* C.)
the brain-box will begin to pull timing.
Think about that one for a moment. You are
cruising along with the OE t-stat at 195* F.
You have your Towd hitched to the back. Here
comes up a 6% grade, but it's a short one, and
you increase the gas. There is a very short span
between 195* and 212* and your coolant temp
begins to rise. It hits 212* F. mid-way up the
hill, and the power--right when you need it the
most--falls off. It is alot better to hit the
bottom of a grade, when towing heavy, at 180*,
instead of 195*....
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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11-29-2007, 09:08 AM
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#2
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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This one is huge..and, of course you have to be out-of-warranty and it will make your rig run
a little dirtier, smog-wise--maybe..
But can you imagine the benefits of running 15*
F. cooler???
There are a ton of them (reasons). There's another parameter,
I was told,--dunno--when the ECM
starts to pull power (timing) out of the
OBD2's timing tables and it is related to
coolant temperature. At 212* F. (or 100* C.)
the brain-box will begin to pull timing.
Think about that one for a moment. You are
cruising along with the OE t-stat at 195* F.
You have your Towd hitched to the back. Here
comes up a 6% grade, but it's a short one, and
you increase the gas. There is a very short span
between 195* and 212* and your coolant temp
begins to rise. It hits 212* F. mid-way up the
hill, and the power--right when you need it the
most--falls off. It is alot better to hit the
bottom of a grade, when towing heavy, at 180*,
instead of 195*....
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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11-29-2007, 09:55 AM
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#3
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Senior Member
Join Date: Feb 2003
Location: Jarrell, TX 76537
Posts: 4,501
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I just pulled up one of may old OBD 2 scans and my coolant temps run about 201 to 205, speed 64 mph, air temp for the MAF was about 72 degrees and running about 20% Load.
__________________
Dale
AKA - Oemy
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11-29-2007, 03:02 PM
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#4
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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Dale wrote:
"..I just pulled up one of may old OBD 2 scans and my coolant temps run about 201 to 205.."
===============================
Dale--
The Allison Tech at Pacific Power told me that
Allison has (in the past) run tests on the effects of cooler temperatures and the lifetime
of the (then) Dexron ATF and the transmission.
A 20* reduction in temperature equals DOUBLE the lifetime of both the ATF and the trans.
At a common running temperature of 15* cooler,
with the 180* t-stat, you are 3/4s the way there. Heat kills Allisons.
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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11-29-2007, 03:57 PM
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#5
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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I did not approach this t-stat swap trick
without some prep work. I wanted to know all of the down-sides.
First of all, running cooler hurts fuel economy, simply because you
are using a heavier, denser A/F charge. The P12
is no economy champ. I knew that. And I wondered
if it would throw a code or maybe not reach the closed loop fuel injection mode.
I paid money to Mr. Goodwrench to check the Anti-Knock Circuit to make sure it was working, after I had replaced a
knock sensor. [The KS's on the L21 Vortec are from the 8.1 L (?) three years BEFORE there even WAS an 8.1 L.] It was 89 dollars to hook up
the Scan Tool (Tech2) and an additional 20 bucks
to run the tests. Cheap insurance I figure.
Then, I cleaned the outside of the radiator, AC
condenser, and engine oil cooler with a mix of
50-50 water and Simple Green. Then I did the
flush and fill on the coolant, getting the Dex-cool out of there. All the while searching frantically for a cooler running BB Vortec t-stat.
A 185* F. t-stat IS listed by AC Delco as an
"alternate" range thermostat for this app.
And I took
the Part Number in hand to our local Chevy Stealership's Parts counter and got the deer-in-
the-headlights look. They had never even heard of it...and...because it wasn't listed on their
computer screen, they would not even try...
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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11-29-2007, 05:51 PM
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#6
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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So, here I was. no cooler running t-stat. And then I found one. Autozone has one in stock. It even
is a quality part in a Duralast Box. It is a
"Motorad" t-stat, all stainless steel body,
with three-bridge HD construction. Motorad is
a well-thought-of outfit from Canada. The AZ
part says Motorad right on it and is their high
flow model. I drove 43-miles, one-way, just to
buy it. Got it home and tested it in a pan of water with a lab thermometer. As I brought the
water up to boiling it began to open at 176* F.
and was fully open at 186* F. A 10* span..Very smooth, no
snap open and snap shut like some bad ones I have tested. Not bad for $9.99..In it went....
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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11-30-2007, 05:26 AM
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#7
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Senior Member
Workhorse Chassis Owner
Join Date: Jun 2003
Location: Palisade CO
Posts: 3,588
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If I understand you correctly you believe the engine runs/operates cooler with a thermostat that opens at a lower temperature.
Is my understanding of what you think correct?
__________________
Clay WA5NMR - Ex Snowbird - 1 year, Ex Full timer for 11 years - 2004 Winnebago Sightseer 35N Workhorse chassis. Honda Accord toad.
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11-30-2007, 06:10 AM
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#8
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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Clay wrote...
"...If I understand you correctly you believe the engine runs/operates cooler with a thermostat that opens at a lower temperature.
Is my understanding of what you think correct?..."
=====================
Clay--
Why do I think you are trying to bait me here?
But I will rise to the bait.
All I know is what my dash gage cluster tells
me. The Temp gage reads 100* F to 210* F at mid-scale and on up to a "fry-the-engine" red zone.
Before the 180* t-stat intall, my over the road
temp read right at 200* + as Dale has posted.
After the install, for 3000-miles, it read one
mark above 1/4 scale. Very nice, and it kept me
well out of any temperature-caused spark retard.
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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11-30-2007, 06:43 AM
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#9
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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Running at the cooler temperature, every rubber
and plastic thingy in the engine bay lasts longer. The hoses last longer. The Belt lasts longer. Burnt spark plug wires become a thing of
the past. Those goofy GM plastic vacuum and fuel
lines don't crack open. There is less heat soak
into the Coach from around the doghouse cover.
Even the dash AC works better. The windshield
washer plastic tank doesn't crack or discolor.
There is no exhaust manifold glowing-in-the-
dark-on-grade...the list goes on and on...
the engine sets no codes and goes into closed-
loop control as always. The heater works and
DW does not complain, because the ramp-up rate
to temp is the same with both t-stats.
And...it pulls like a freight train.
But the biggie is the health of the Allison is improved.
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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12-01-2007, 05:21 AM
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#10
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Senior Member
Workhorse Chassis Owner
Join Date: Nov 2005
Location: chokoloskee, fl 34138
Posts: 717
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Thanks Steady Eddy, I am going to try that 185 T.
Did you change to regular green antifreeze?
__________________
2016 Dynamax DX3
USCG Ret BMCM
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12-01-2007, 05:54 AM
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#11
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Senior Member
Workhorse Chassis Owner
Join Date: Jun 2003
Location: Palisade CO
Posts: 3,588
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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Steady Eddie:
Clay wrote...
"...If I understand you correctly you believe the engine runs/operates cooler with a thermostat that opens at a lower temperature.
Is my understanding of what you think correct?..."
=====================
Clay--
Why do I think you are trying to bait me here?
But I will rise to the bait.
All I know is what my dash gage cluster tells
me. The Temp gage reads 100* F to 210* F at mid-scale and on up to a "fry-the-engine" red zone.
Before the 185* t-stat intall, my over the road
temp read right at 200* + as Dale has posted.
After the install, for 3000-miles, it read one
mark above 1/4 scale. Very nice, and it kept me
well out of any temperature-caused spark retard. </div></BLOCKQUOTE>
No I wasn't trying to bait you, just wanted to make sure I understood what you meant before I made any comments.
I don't understand how the thermostat can affect the operating temperature of the engine after it is fully open unless the temperature drops low enough for it to begin to close.
Once up to temp - about 198 in my case(as shown in digital form by my ScanGauge display) the temp stays at that point or higher. The engine fan comes on at about 210 degrees and goes off at about 206 degrees.
There doesn't seem to be an opportunity for the thermostat to affect the temp.
Maybe I am missing something in the way the thermostat works.
__________________
Clay WA5NMR - Ex Snowbird - 1 year, Ex Full timer for 11 years - 2004 Winnebago Sightseer 35N Workhorse chassis. Honda Accord toad.
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12-01-2007, 06:01 AM
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#12
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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Ron--
With my BB Vortec, it was a 15-minute change-out. Most of that time was me looking for the right Metric tools. You will lose between 2 and
3 quarts of coolant. If you do not like the results, the swap-back to the 195* t-stat is easy.
I chose the Prestone pre-mix yellow coolant, from Walmart, after much looking and hand-wringing, NOT the Dex-cool Prestone in the silver-colored jug..the Green, for me, was/is
very hard to find, although it'll work OK. The P12 has a huge ($$) MD Truck up-right Aluminum-cored radiator (not a crossflow) and I wanted the aluminum protective features of the yellow Prestone Pre-mix. I did the radiator core exterior
cleaning and the coolant swap before the t-stat
trick and topped-off the radiator surge tank with distilled water, trying to dilute the coolant down to a 60% water/40% anti-freeze mixture, as it transfers heat better, I live in a warm place, and then I
didn't need any Water-Wetter. Don't forget the
GM-Genuine coolant tablets!! Two per re-fill..
they come five in a pack from Chevy.
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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12-01-2007, 06:32 AM
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#13
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Senior Member
Join Date: Apr 2006
Location: The Great Pacific Northwet
Posts: 382
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Clay wrote:
"...Maybe I am missing something in the way the thermostat works..."
===============================
Clay--
I thought the same EXACT thing. Your t-stat
modulates (sp) ie, Floats, between open and
shut. When "on-control" it is never really
wide open and it is never really fully shut.
It is "hovering" around the set-point of the
OE t-stat at 195* F.--probably (+) or (-) 10
degrees with a smooth t-stat. Your Aux cooling fan(s) tip in at a pre-determined temperature
to help the t-stat get on control.
On that 6% looong Grade, all bets are off...
the coolant temperature rises very rapidly,
the t-stat DOES go to wide open, OUT of control,
the Aux fans are screaming the BIG clutch main
fan starts howling and the whole mess goes into a state of shock.
The only way left for the brain-box to cool the
engine, and prevent damage, is to pull back the
engine's timing--spark retard. With the resulting net loss of power..with the use of a 180* t-stat you lengthen the TIME between on-control cooling and out of control spark retard.
__________________
Steady Eddie/1999 KSCA 3357/P12 Chassis/454 Vortec L-21
Allison transmisson
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12-01-2007, 06:51 AM
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#14
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Senior Member
Workhorse Chassis Owner
Join Date: Aug 2007
Posts: 480
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Is there a possibility that his 195* thermostat was balky or on the high side of the allowable operating range and a new one could have performed better? Was that checked out? I reviewed the post and didn't see that in the prep message.
Joe
__________________
Joe & Sherri
2004 Winnebago Adventurer 37B
UltraPower
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