I'm cool, do you think I'm cool? I think I'm cool. (question on being cool)

[NVW]

The rubber gasket has a groove on the inside edge, the outer edge of the Tstat fits in the groove. It makes a nice seal.

 

[Husker6.5]

The ones that use the rubber also use it to seal the thermostat from leaking coolant past it. So even tho its not leaking externally it might be letting coolant past internally simulating a stuck open stat.

Yes, that rubber split O-ring that goes around the edge of the T-stat is crucial to prevent coolant from going past the edge of the flange and around to the radiator side of the T-stat. That 1mm around the edge would be like having a 3/8" hole drilled through the T-stat flange.

 

[Hink]

All that is true but just so people don't get confused, with mine on the '93 there is no rubber gasket. It is a paper gasket.

 

[THEFERMANATOR]

The rubber seal were talking about has NOTHING to do with the t-stat to housing. It goes around the actual poppet in the stat itself to make it seal off tighter so that no coolant can get past the poppet. I believe you said you changed senders, if so you are running nearly axactly the same point on your gauge in your 1st pic as I was with a 180 stat and 3 different senders in my 95. The new senders are not calibrated correctly, and it throws teh gauge off about 1-1.5 hash marks from where it should be. As the temp goes up, they read closer to correct as mine reads about 185-190 when it reaches 195, but when the engine is cooler, it reads way low.

 

[THEFERMANATOR]

Look at this picture. See the black portion below the housing, thats the rubber seal around the poppet valve. It tightly seals off the stat until it opens to prevent ANY cooling from bypassing until the stat is up to temp. ONLY the OEM AC DELCO has this to my knowledge(not even the cheap AC DELCO has it, and they are no better than the $5 cheapy's). You will also notice this is an all around different designed stat, and is of a MUCH higher flow design than the internal poppet like the cheapy's use.

 

[Hink]

Oh man, sorry about the confusion. I know you kept saying poppet, but it just wasn't going in my brain.
See? pictures are good! : )>

 

[JayTheCPA]

And no, the gauge is not linear. The bottom mark is 100(even though 95+ diesels start at 160, it is actually 100), the next is 180(verified 3 different clusters that this mark corresponds to 180 degrees for resistance), then 210 is straight up, and it's pretty linear from there over with roughly 235 at the next hash and 260 at the top.

So *THAT* explains the wide temperature variances from the dash to ECM readings that I see when the motor is warming up. And why once the motor is up to operating temp the dash and ECM appear more in synch . . .

Seems that my plan to replace the dash analog gauge with a dual digital gauge (readings from both heads) will solve this

 

[Will L.]

You guys have it good with pillar mounted gauge options. You can't fit those in a hummer. For the love of--- please people-- you have a truck known for dying from overheating- buy a quality after market gauge.

Can anyone tell me of any truck or car that underwent so many coolant changes in the design?

Jay- you get 1 like only cuz I can't give you 10 on that response.

 

[Hink]

BTW, to compare with the picture in the original post, here's the gauge with the 195* AC Delco thermostat on the same road at the same speed.

 

[THEFERMANATOR]

BTW, to compare with the picture in the original post, here's the gauge with the 195* AC Delco thermostat on the same road at the same speed.View attachment 47726

Thats about 185-190 on the gauge, so it's not that far off really.

 

[GM Guy]

Oh wow, yeah that blows.
And yeah, let us know what happens there, I'm curious to see how all this works out.
I'll try to look in to an ir gun tomorrow.

@Hink
Sorry I didnt get back to you sooner with results.

New sending unit may have improved accuracy somewhat, but the guage still reads high.

I plan on putting in a Kennedy clutch and a OEM 97+ 9 blade steel fan on this for now, and eventually going with the full upgrade, 00 pump, Leroy Diesel fan clutch system, and either a 9 blade steel or a plastic Duramax fan, and sticking with the single t-stat system and Leroy's special application Delco t-stat.

The current clutch seems inoperative, so I will know more once I get a good one on as far as temps being actual or not.

I See you have the Kennedy clutch. how do you like it?

 

[GM Guy]

questions for all after reading the entire thread:

1. does the gasket and bare metal flange of the t-stat seal good, or do I need the rubber flange gasket? I am rocking a thicker blue Fel-Pro gasket on my Leroydiesel AC Delco t-stats in 3 trucks.
   
2. do you think that there is any merit to running the recommended quick connect on the heater line? Just for giggles, I had the dealer get the part number via VIN, and it is different than the gassers. all I can see is that the seem to have a plastic restrictor that is in the path of the coolant. It is part number 15650056. I am curious that a barbed fitting lets too much flow through.
   
3. I assume blocking off the heater entirely is a big no-no as far as air purging and steam pocket issues, correct?
   
4. for mounting an extra guage, is a drilled and tapped crossover blockoff plate suitable, or does it really need to be down in the OEM left head location (aka, back right)
   
5. Just how bad are replacement water pumps? this 95 looks to have a recent pump, and judging by the POs buying habits, the parts were whatever Carquest or Napa had for sale. I am wondering if this is the root of my issue.

 

[NVW]

Personally I like the rubber flange gaskets but the other ones work. Once the air is out of the system I see no problem having a valve to close the heater from the loop. Both my back blocking plates are drilled and tapped for future gauges.

 

[Will L.]

I see no problem with rear block off plates for gauge temps. Different waterpumps are hit or miss. Without knowing exactly which it is, it's a crap shoot.

I ran a Kennedy fan clutch before on my 4 bolt pump with descent results, I am currently running the Hayden severe duty, It's a bit better.

The gasser quick connect heater hose has no restrictor in it. I HATE the quick connect- it was only adds to save time on assembly line. In the oil company fleet when we got a new truck, before it went out in service we swapped it for a barbed fitting and piece of hose.

 

[Hink]

@Hink
Sorry I didnt get back to you sooner with results.

New sending unit may have improved accuracy somewhat, but the guage still reads high.

I plan on putting in a Kennedy clutch and a OEM 97+ 9 blade steel fan on this for now, and eventually going with the full upgrade, 00 pump, Leroy Diesel fan clutch system, and either a 9 blade steel or a plastic Duramax fan, and sticking with the single t-stat system and Leroy's special application Delco t-stat.

The current clutch seems inoperative, so I will know more once I get a good one on as far as temps being actual or not.

I See you have the Kennedy clutch. how do you like it?

Cool, thanks for getting back...
Tomorrow morning I am leaving for N.D. pulling an RV where I'll be able to really see the cooling system in action but so far, on shorter trips pulling the same fifth wheel, I've been very happy with it. The copper core/brass tank radiator, Kennedy fan clutch with his matching 9 blade fan, 180* thermostat, high flow water pump and Red Line water wetter has definitely brought the cooling system up to the level that it needs to be.
Of course, I now know that I need to change back to the 195* stat when I am not going to be towing long distances because the system cools so well now, I have a hard time (like, almost never) getting this 4 ton behemoth up to operating temp even at freeway speeds when I'm not towing. And the fan clutch will still always kick in at 180* so that'll be a little wonky, but that's a minor issue.
I'm thinking that my gauge is fairly accurate (within Therms' guide from this thread, i.e. first large notch is 180* and getting more accurate from there) since my IR thermometer read 177* right on the sensor when the gauge read 180*.
As for the water pumps, I installed mine from SS Diesel before I became more educated on these engines, I'll make sure that I have the pump from this article next time, I really respect the process that they went through to get the info (It may be the one I have on already, I don't even know)... http://www.maxxtorque.com/2009/09/heath-diesels-65l-diesel-heavy-duty.html?m=1
"At the conclusion of an exhaustive evaluation, we had determined a clear and decisive winner in the factory service replacement water pump: part number 88894035"

It's looking like the single thermostat housing may be the ticket for these engines... it definitely is for me and like Will, I removed the shit quick connect for a barbed fitting and hose and never looked back or had any issues.
Even the cheaper thermostats have sealed fine for me. I had an issue with a leak recently but all it ended up being was not having the housing tightened down enough - derp.

 

[JayTheCPA]

I assume blocking off the heater entirely is a big no-no as far as air purging and steam pocket issues, correct?

From what I have read, possibly / probably. I use a manual valve in the heater line and just leave it ~1/4 open all the time. Even down to the Teens F, this setting is good enough to keep the Burb's cab warm. Also keep it in the 1/4 open setting during the cooling season as there are always cool mornings and it helps with defogging the windows on rainy days.

for mounting an extra guage, is a drilled and tapped crossover blockoff plate suitable, or does it really need to be down in the OEM left head location (aka, back right)

It depends on where you want the reading. Consider just using the existing port in the passenger side head as you will then get a more complete picture of what is happening across the motor.

 

[FellowTraveler]

The GMT400 C/K upfitter manual call's for a loop in the heater line if you bypass the heater cores. Depending on the year the loop would go from t-stat housing to radiator steam vent line on later radiators w/o cap, the early rads w/cap don't appear to have a steam vent port on the radiator "highest port on passenger side rad tank."

 

[Will L.]

When filling system with coolant to eliminate air pockets on all vehicles you are supposed to turn the heater to max while filling and checking system. Once full you can shut off flow completely. Systems that require constant flow will use the 4 hose valve as a bypassing method instead of a 2 hose valve that just deadheads flow.

 

[GM Guy]

@Hink , any trips recently to try it out?

I need to get installed in the next day or two the Kennedy clutch, 9 blade fan, and lower bumper airdam.

I am considering putting the OEM heater line and quick connect back on. PO has a barbed fitting and hose. I guess we must be lucky, because I have never had issues with a quick connect. if she looks crusty, I will change it.

Then, a trip off to Nebraska to try it out.

 

[Husker6.5]

Where to? Swinging up to Lincoln?