Thermostats

[joegoodrich]

I see that ssdieselsupply.com sells a 180 degree thermostat kit for my 99 6.5 diesel. Originally it came with (2) 195 degree thermostats. I find that my rig runs about 200 all the time and when I accelerate hard it jumps to 210 then drops back down to 200.

When I tow my boat the truck runs at about 220+ in the summer heat.

I just replaced the fan clutch -- it was shot.

What are the benefits of the 180 thermostats vs. the 195's? The guys on the hummer forum seem to think I should just stick with the 195's.

((((Truck is a 99 Hummer H1 -- 6.5 Turbo Diesel))))

[Shooter]

Have you replaced your stats since you have had your H1? I found that the ones from NAPA do not function properly in my '00 wagon. I believe that they have a longer travel and therefore bottom out against the rear of the housing or in theory open on one end close on the other. When driving around town they work fine but when under a load and a wide open stat is called for they restrict the travel of coolant causing the temp to climb until the load is reduced. I'm going with the 180's from SS. I can let you know if they work any better. Also redline water wetter is a good additive.

[Scrufdog]

i replaced my thermostats with SSD 180 stats. However, when towing late this summer, my engine temp would hang around 190-194, and get as high as 230. Seems the thermostats were just staying open, as there were no heat cycles in the engine temp (all logged with obd2 software). So, this spring I'm gonna drop a set of factory stats back in. This way I can see if the higher stat temp will allow for proper circulation, and heat cycling on the coolant.

[Garth J]

Check out Walts upgrade fan kit. I found it really keeps the temp down and well worth the money and moves a lot of air, I pull a 27 foot 5th wheel RV and dodnt have any heat problems at all..


94 GMC K2500 ex cab short box 80hp chip, heat-sync, air induction, 4 inch exhaust, upgraded water pump, d-max fan kit. #9 resistor, A-pillar 3 gauge kit and probably more that I cant think of ...300.000 Km runs like a top

[joegoodrich]

I considered using the upgraded fan and 15 degree sooner clutch but my fan shroud doesn't have enough clearance. My current fan is 20" and the new one is 21"

The fan would have to be trimmed and I don't know how to do that and keep it balanced.

[Garth J]

I think you will find the fan fits perfectly mind did with no trimming at all.
A big difference going from a 6 blade to a 9 blade it sure solved my heating problems on long hills towing my 5th wheel....Garth

[joegoodrich]

Garth,
My truck has an 8 blade plastic fan -- very similar to the duramax upgrade fan. The problem is with the Hummer H1 is the fan shroud is very tight to the stock fan -- maybe a 1/4 to 1/2 inch to spare all the way around.

My understanding is that the factory hummer fan clutch (99 Hummer with screw on fan clutch) has different spacing to bolt on the fan blade than does the fan upgrade kit. This means I can 't even use the upgraded fan clutch with my old fan blade.

[Garth J]

Right I dont know about the Hummer fan so what id do is replace the thermostats down to 180 deg. The last thing you want is too much heat ..Garth

[Shooter]

Make sure you have the correct serp belt. I just put a new engine in my H1 and the 101.5 inch belt that it calls for would be tight but the index marks were off and the tensioner would sit almost vertical. The engine temp would creep up under load and I'm thinking the belt make have been slipping causing the H2O pump and the fan to become less efficient. Im running 195 stant stats with a 101.0 inch belt and now the temp sits just left of 200 all the time. Have a set of 180 on there way but I'm probably going to keep them on the shelf unless I have any more trouble.

[joegoodrich]

I was having the temperature fluctuations 195-210 degrees with ambient temps outside at 40 degrees. 210 with mild load put on the engine.

Last summer the truck would run 230+ while towing an 8000 trailer.

I replaced the fan clutch that was shot, but the temperatures didn't change much.

I installed the 180 degree thermostats and SUCCESS!!!

The engine runs 180 degrees SOLID even with hard acceleration.

My guess is that one of the factory 195 degree thermostats was stuck closed -- so I was only getting 1/2 the flow.

Is there a simple way to test the old thermostats?

[6point5]

you can accurately test thermostats by heating a pan of water on the stove with a rack in the bottom of the pan. Place the thermostats on the rack making sure they are completely submerged but not touching the metal of the pan. Use a cooking thermometer making sure it is only in contact with the water, not the pan, and just continue heating while watching the thermostats. When you observe them start to open, note the temperature and once they are fully open, note the temperature. Heat the water fairly slowly because you want to be sure that the thermostat opens to wide open within five degrees or less.

This is an exact test of inexact equipment. Many thermostats vary from their advertized temperatures right out of the box. I have tested them as far as 25 degrees off when brand new and returned them for another one. They should be within 5 degrees different at the most.

[sixnickel]

One thing I have found with thermostats on these things, if you go to your local auto parts store and get a Stant or a Gates, or any other generic brand, you will have overheating problems. You must run a Robert/Shaw style thermostat because when its open, it will pass twice as much as the regular style thermostat. I have had the best luck just going to the dealer and getting an OEM replacement. If you have the time to wait for it, you can order one from Walt also. I learned on my 6.2L back when it was naturally aspirated, that with a Gates/Stant/generic thermostat temperature was OK until a long hard pull on a hill, temp gauge would creep up to about 210 get over the hill, pull the power and right back to 180. It did this whether it was 90 degrees out or 10 degrees. Put in an OEM AC Delco, which is a Robert/Shaw style and looks completely different, and the gauge never moves off 180, even with the Banks Sidewinder on it, no matter what you do. One other thing, when the Banks went on, I installed a 100 gpm Penninsula water pump. You learn from experience (experience is a whole bunch of mistakes).

[TAZZ9963]

Make sure that your'e cooling path throught the radiator is clean and anything else that is in front of it. I would flush it from the engine side with just a regular garden hose and blow out all that road debris. That might help.

[RckyMtNDeZL]

I have pondered this very subject...my buddy runs a suburban, no fan upgrade, just flushed his old coolant, and replaced his stock 195 for a 180 he got at autozone...hasnt pushed the red line of the temp gauge since. We did get real hot once, but it leveled off when he downshifted to 3rd.

[RAYMONDK]

You will pick-up an additional 15% cooling capacity by changing to straight water. Use softened water with an anti corrosion additive. Antifreeze is corrosive and has a 15% lower specific heat than water. You don't need antifreeze unless you are exposed to freezing temps. MY Benz had A/C and over-heated in the summer. so I switched to water and no more over heat. I don't know why but my 96 6.5 TD stays on 195 unless its 95 deg pulling with the A/C on. Cutting the a/c drops it back . The things just need 25% bigger radiators to get past all the problems from the heat.

[Garth J]

to test them you need a thermometer and a cup then suspend the stat over the cup ( popsicle sticks work well) with the sensor down put the thermometer in the cup and pour in boiling water it should open immediately and start to close as the termp drops and read the thermometer for the temp.

[RckyMtNDeZL]

After all this debate I went and got my 180 t stat. And I must say I am very satisfied with the results I got from it. Cooler is better. I cant believe I didnt swap out the OE junk I was running with sooner. If it wasnt for SSD most of us would have sold our 65's long ago Im sure. The highest my temp has gotten since then is around 185 until it opens and the guage drops down to cooler temps. Cheapest and best upgrade thus far....many more to go!:D