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Gentlemen, I have done a few searches and I just want to be sure: That these Cummins engines are the coolest running motors around. I have driven this truck about 500 miles since owning it and I have learned it takes forever to warm up, and when it does, a red light will knock the gauge back down to lower normal. I think its great, and though the wife wants the heat on full blast in June, once the truck warms up to mid gauge, the heat is HOT HOT HOT! I already made some homemade winter fronts to fit in the grille with some custom cut black acrylic sheet, so I'm asking- This is normal or no? AP

Recently bought my 2nd 97 12v. Currently has a long warmup cycle 20 miles + and was going to replace the thermostat (with a big block per Michaels suggestion) Turns out I have a small amount of oil in my coolant :sad4:. both the thermostat and oil cooler have formagasket and the heater core was recently replaced. I am suspecting that the oil cooler was recently checked or replaced and perhaps the form in place gasket is not so good. Question is what year make and model thermostat do you suggest? Secondly does the oil cooler break down and leak with age like the heater core? I do not seem to have coolant in the oil and am hoping it's a problem that replacing the gaskets on the oil cooler will fix. Hopefully not a blown HG. Any suggestions welcome.ThanksRich

As some of you here know I have had a over cooling condition in my truck for quite a while. It seems to be getting worse. No matter what tstat i am using now the temp is hard pressed to get over 175 and will drop to 155 but seems to stay just below 170 most of the time. This is in 70 weather, in town or high way and with 2 of my winter fronts in place. I am on my 7th tstat with the same results. I even sent one of them to Mike and it runs fine for him. After 6 190* tstats and one cummins 180* tstat with almost the same results with them all I am at my wits end. I have also replaced the temp sender twice and no differance. I am wondering has anyone else here had this problem. Not long ago I replaced the heater core and refilled the engine thru the tstat hole and even put water in thru the heater supply and return. I cant beleieve there is any air in the block. The gauge will move between 155 and 175 but I cant get it any higher unles I am pulling the rv. But even then about 180 is the best I can seem to get.. I have noticed of late it the temp drops below 165 i get some EGT fluctuations and a little boost gauge fluctuations. If any body has had this problem I am very interested in hearing about them and any solutions you might have found.

I've had 2 NAPA thermostats fail since the first of the year. Just wondering if anyone knows of any particular reason why they could be failing aside from poor quality in the first place and what others are using Cummins or aftermarket?

Hello all I am new to this forum and hoping to find some insight. I have a 98.5 with the following mods,Edge juice with attitude, turbo modified by Gillette diesel, 275 RV injectors AFE intake and 4" turbo back.What i am seeing is some weird temp issues. Truck unloaded sitting at a stop light will start building temp for no reason starts at 180 and sometimes will go up to 190 or higher, ambient temp plays no factor will do it on a 55 deg morning or a 90 deg day. Differnt from one stop light to the next. Took to my local shop that helps me out strapped down to dyno duplicated problem but here is where it gets weird, one pull the truck wont break 190 with a 60% load applied via the dyno next pull truck truck hits 230 easily and once in a great while the truck will puff a tiny cloud of white then right back to black out of the exhaust. Fan clutch cycles normally, coolant shows no signs of combustion contamination not a 53 series block water pump looked great and truck uses absolutley no coolant. Radiator is five years old was clean externaly and passed flow test at the radiator shop earlier today. T-stat is probably 4 years old and this is the 3rd one but last time i replaced it the sympotoms were not like this. Engine has 102k on it and probably gets 3 to 5 k a year on it? i would really appreciate some feedbackThanks in advace

Had a funny idle this morning. I have a 2.2k ohm resistor in my iat sensor but I dont see how it would have anything to do with it. Cranked up and drove to work this morning and all was fine. Got in my truck a couple hours later to go to my next store and truck cranked up and idled fine a few seconds then it idled to about 950 or so then back down to 800. It did this on and off for a minute until I put it in drive. Then got to my next store and it was doing the same thing when I parked, it would idle like this for 3-5 seconds high then 3-5 seconds low. I reset the apps and then came back out in a few hours and the truck was doing the same thing. Next store I reset the apps and it has been fine since. Not throwing any codes either, any idea's?

I had some errands to run today and drove the truck. As normal the temperature came up and held steady at 190*. I stopped at the local station to top off the fuel and left the truck running.It was in the low teens here in Michigan today. I know it's colder in other states but.............By the time I had topped off and went in to pay the temperature had dropped to about 160*Why..........

Alright been messing with this for a couple of weeks. Started when it first got cold. Noticed my heat was not as warm as usual. I checked my radiator and it was about half gallon low. After I filled it up I drove it and the heat seemed to be better. When I got home I noticed some antifreeze on the ground. Looked up there and found it dripping from the drain plug. Replaced the plug which I might add is a stupid design and pretty much worthless to actually drain your radiator. Why cant it be a pitcock drain. NOOOO it has to be some nasa frickin design with an O ring that doesn't actually work after you remove it the first time. :banghead: Sorry !! Anyway it wasn't the plug anyway but a leak in the radiator up a little higher behind the shroud. Ok now this is where I get lost. This is a closed system and it will build up pressure. Why is it just dripping ? Why isn't it spewing out making a mess ? Ok so I get a new radiator and install it. Replace the t-stat got it at O'reilly's and flush the engine and then disconnect the heater hoses and pour some clr in the heater hoses and let it sit in the heater core for about and 1 1/2 hours and then flush the heater core and reconnect the heater hose. Then fill the truck up with water and then I let her run a bit cause I want to make sure I am getting flow thru my heater core so I pull the hose off on the block side of the heater core and it is pumping good then I pull off the hose on the other side of the heater core and it comes shooting out. Then I drain it again and put the truck on slight upward hill and refilled with antifreeze. Also replaced the resistor on the blower. It went out in the middle of this. Also checked the door where you switch from AC to heat it works fine. Also checked the temp selector thingy underneath there it corresonds with adjusting the temp control. It spins around and stops.Take her for a spin the truck heats up to 190 heater seems warmer ? This truck has always heated up to 190 and would move a neeedles width either way while driving. The heater has always been hot and usually if I have plugged it in after a ten minute warm up it was very toasty. Ok now that I have replaced everything the truck is very slow to reach temp at idle. While driving @ 60mph my truck will reach 190 or just a hair more but when I slow down for a stop light the temp drops down to 160 or so and then as I accelerate the temp will slowly work back up to 190. My heat is warm at best but by no means is it hot. I just left work idiled in the parking lot talking to my friend for about 20 minutes and then drove home from work 25 miles mostly 60mph. I get home and pop the hood nothing is really hot at all. The radiator is not hot or even really warm. The upper hose has some pressure on it but it is not hard to squeeze. It's warm but not real hot. The heater hoses are a little warmer. So I touch the cap and it's not even warm so take the cap off and there is just no pressure at all I look into the radiator it is still full and there is no flow in the radiator at all. I feel stupid that I can't figure this out. The heater prob could be the core. But when I pulled the heater hoses I had good flow going in and out and the water was hot. (ouch dumbass). So I am thinking it is not the core. Why is there no noticable pressure at the cap ? Why is there no real pressure in the hoses ? If it is not pressuring up you would think you had a leak ? But I don't. Why is the temp of the water seemingly not very hot ? T-stat staying open ? Then I would think I would see the antifreeze flowing thru the radiator ? But I don't. Water pump not working ? Then I would think the truck would over heat or at least get hot ? It doesn't. For some reason the cooling system is not getting hot enough. It is not creating any pressure either. It is not cold enough here to require blocking the radiator. Never had a prob before. I am sure it is a simple fix but I am just at a loss as to what ? Why does it get to 190 and then drop back so far ? Why will it not hold the heat. Before it just stayed at 190 within a needles width either way. Sorry for the long post. Any help would be appreciated. Thanks Rob

Do the cummins brand of t stats have a fail safe?The question is when they go bad are they made to brake in the open position? My engine gets hot 190.The t stat housing is hot. The radiator fluid is cold.I am thinking water pump. The radiator and heater core were flushed in summer.

hey all,i flushed my engine coolant and changed the thermostat sunday afternoon. before, my truck would take ~3 miles or so before the gauge read above 140. once warm, my needle would stay above 140 but NEVER cross 190. since the flush i can reach 190, often before i'm out of my neighborhood. while driving, the needle bounces either side of 190. i have also noticed that the overflow resiovor has more fluid than when i finished the flush(i keep expecting to put more in). the thermostat was one from the local oreillys(murry brand, i believe). is these normal, or do i still have air in the system? it is a little unsettling to see something different from on a cluster you've been staring at for 3 years.