Running a bit warm

[TFaoro]

Hey guys, so since I've had my truck for a bit the engine temps are acting a bit weird. I know it's normal to climb up to around 200F before the thermostat opens, but mine seems to be doing it sporadically after the thermostat opens. For instance, driving home there was a bit of a grade for about a mile, and the temps climbed up to 208. The fan kicked on and it cooled back down. Then today, I was driving for 30 min or so and it was at 193, where it usually sits. Then out of the blue it climbed to 202 and sat there until the fan kicked on and it cooled back down. Ambient temps were both around 65*. I'm thinking thermostat, but it didn't do this before the new water pump.

[CSM]

Thermostat is easy to check.   Could have some rtv stuck in it.

[TFaoro]

Maybe my brain isn't working.... how do I check it?

 

Better not be any in there. I haven't used it on anything. 

[notlimah]

MIne will do something similar.

 

My temp when fully warm usually stays right at 190 (according to dash gauge) and here and there it'll climb to 195-200 depending on how hard I'm driving and then the fan will kick on and it'll drop down to 185ish range and then slowly climb back to 190 depending on how I'm driving.

 

Seems normal to be, unless those sort of fluctuation while empty or not driving grades is no good then maybe mine is jacked up too!

[Mopar1973Man]

The only time my temperature will climb away from the normal 190-200*F zone is when the pyrometer is above 1,000*F. Then the pyrometer dictates how fast. So if I'm towing up a grade holding 1,200*F it doesn't take long to climb to 205-208*F to lock the fan. Everything below 1000*F EGT's won't make the coolant temperature change at all.

 

EDIT: Digging through my logs I've been hard pressed to exceed 197*F on a empty truck.

Edited May 11, 2016 by Mopar1973Man

[Buzzinhalfdozen]

Is it possible there's still some air in the system?

[Mopar1973Man]

2 hours ago, Buzzinhalfdozen said:

Is it possible there's still some air in the system?

 

This is why I always leave the thermostat out till I get the block right to the edge of the thermostat. That way all air is forced out and you drop in the thermostat and bolt it down and hook up your hose and top of with the last half gallon or so of coolant and your done.

[TFaoro]

11 hours ago, notlimah said:

MIne will do something similar.

 

My temp when fully warm usually stays right at 190 (according to dash gauge) and here and there it'll climb to 195-200 depending on how hard I'm driving and then the fan will kick on and it'll drop down to 185ish range and then slowly climb back to 190 depending on how I'm driving.

 

Seems normal to be, unless those sort of fluctuation while empty or not driving grades is no good then maybe mine is jacked up too!

 

I don't think that's normal.... BUT the dash does lie. Having a scangauge or something similar would really help!

 

3 hours ago, Mopar1973Man said:

The only time my temperature will climb away from the normal 190-200*F zone is when the pyrometer is above 1,000*F. Then the pyrometer dictates how fast. So if I'm towing up a grade holding 1,200*F it doesn't take long to climb to 205-208*F to lock the fan. Everything below 1000*F EGT's won't make the coolant temperature change at all.

 

EDIT: Digging through my logs I've been hard pressed to exceed 197*F on a empty truck.

 

My egts stay below 900 on the steepest hills unloaded, leading me to believe there's some sort of problem. 

 

2 hours ago, Buzzinhalfdozen said:

Is it possible there's still some air in the system?

I took the thermostat out and filled it until the bock was at the brim, so I'm not sure how air would still be in there. 

[notlimah]

I'll have to start driving around with the ODB hooked up so I can get a good log going on. The truck has a brand new radiator on it and since the radiator is overkill for these trucks it seems like the truck just can't always make fine tune adjustments. Like it'll get a little over 190 then it'll cool it down, but it can't cool down to precisely 190 so it goes a little under then the truck tries to compensate and it just turns into a game of over/under compensation until you get back on normal, level driving.

 

That's my logic on it. I don't see how a temperature fluctuation of 185-195 is that bad on these older trucks. But please, someone school me up if I'm wrong!

[Mopar1973Man]

The older 12V tend to play that game more so because of the location of the temp sensors. 98.5 to 02 the temp sesnr is right at the thermostat so your seeing the hottest coolant right there. Back in the 12V they had the coolant sensor at the rear of the engine so by the time the coolant cycled and the coolant dropped enough to close the thermostat the coolant at the rear of the engine was colder. Hence the wide change of temp on a 12V vs our where it might rise and fall 10 degree roughly. Depends on the thermostat. Like mine pop open initial close to 200*F and then falls to 188*F then becomes stable at 191-193*F never changes unless towing.

[notlimah]

All my numbers are straight from the in dash gauge so I may be a little off on my numbers. I'm going to start driving with my tablet so I can get more accurate numbers.

[dripley]

i running my scan gauge and it reads true to the gauge as best as it can. Mine takes crazy swings down when it wants to and the scan gauge, although it is slower, tries to follow the gauge. The other day the temps wigged out. I was seeing anywhere from 90* to 185*. Just bouncing around like crazy. I noticed it while ideling when the exhaust brake kept cutting in and out. Got to poking around under the hood and noticed the slide that locks the wiring harness connector to the VP had slid out. i pushed the connector and slid the lock back in place and the gauge settled back down and has not done it since. 

[notlimah]

So a connector that was hooked up to the VP was loose and causing coolant temp swings?!

[dripley]

It's the main wiring harness connection. Yes, when I pushed it tight and slid the lock in place it stopped the craziness. Have not looked at a wiring diagram to see what that could have had to do with it. 

[notlimah]

That's weird, I'm going to check mine now.

[dorkweed]

Have you done Mikes crankcase vent relocation Mod????  The OEM vent spews oily vapor that gets stuck to the cooling fins on the radiator, which attracts everything else (dust, pollen, dog hair, cattail fluff, etc).............which makes for a radiator that don't cool worth a crap.  I used to treat my '99 with some detergent in a spray bottle followed by the  garden hose to clean the "goop" from the fins on the radiator.

 

[Dieselfuture]

I have drilled a very small hole (smallest drill bit I had) in the thermostat plate for air to escape without any issues. 

[Mopar1973Man]

Why not do the easy thing and leave the thermostat out till the block is completely filled right to the edge of the block. Now install the thermostat and finish filling. Never have an air issue then.

[Dieselfuture]

I also did what you said Mike, fill the fluid till it was flush with thermostat. But just in case if there is any air is in system it will always escape through that tiny hole. I've done it on other vehicles before with good luck, some thermostats come with a small check valve in them too.

[TFaoro]

10 hours ago, dorkweed said:

Have you done Mikes crankcase vent relocation Mod????  The OEM vent spews oily vapor that gets stuck to the cooling fins on the radiator, which attracts everything else (dust, pollen, dog hair, cattail fluff, etc).............which makes for a radiator that don't cool worth a crap.  I used to treat my '99 with some detergent in a spray bottle followed by the  garden hose to clean the "goop" from the fins on the radiator.

 

Not quite Mike's, but one of my own... The front cover breather runs down, along the bottom of the engine, and dumps out next to the control arm. The 12V breather dumps in the same spot.

 

It was fine today... 193 all the way home. I guess I'll just see how it acts.