Engine/Transmission (1994 - 1998) Temp gauge not moving?

[BillBaker]

Ok so I decided to do a coolant flush. Truck is 98 2500 12 valve. I drained the coolant and decided to change the thermostat while at it. I had a hose in the inlet with the top radiator hose pulled for the flush. I ran the truck for a good 20 minutes (outside temp where i'm at is currently in the low 50's) and the temp gauge did not move nor did any water flush out. I thought maybe it was the thermostat so I took the new one out and put the old one back in. This time I had water flush out but the temp gauge still has not moved at all.Any thoughts what the issue is?...no issues before I started this,just wanted to change coolant.

 

[BillBaker]

Ok so now that I had flow enough to flush out the coolant i did that and added new coolant. I ran the truck again with no reading past 140 degrees (where it sits and does not move at all-the temperature) and it appears that the coolant is not flowing through the system as I got 4+ gallons in it when I filled it and it's not taking anymore.. could this be the thermostat is sticking (even though I had flow out of the top radiator hose when I flushed it?) This is my first flush and thought this would be a simple procedure.

 

[Missouri Mule]

Usually you only put 4 gallons of coolant/distilled water(1/2 and 1/2) unless your using over priced premixed coolant. When I have drained or flushed antifreeze/coolant/water out of my radiators (different vehicles) I take off the lower radiator hose or the hose going into the water pump.







Remember your t-stat reads temp from the bottom when the temp reaches a certain temp the top of the t-stat moves upward letting coolant go into top hose/ radiator then the coolant goes down and cool coolant goes out bottom hose to water pump.

 

[BillBaker]

Ok...I did pull the lower radiator hose also. So maybe the 4 gallons is good but still cant figure out why temp gauge is still at 140 and doesn't move

 

[GAmes]

Have you driven it? These engines don't heat up well when the truck is stationary.

 

[BillBaker]

No...it got dark out and I didn't want to risk anything just in case as I live pretty rural. I plan on doing that tomorrow ....also, based on experience I thought running it about 20+ minutes and mid 50's temps outside that it would warm up. More I read it sounds like a thermostat but not sure. It was the 180 degree t-stat from Geno's.

 

[GAmes]

It was the 180 degree t-stat from Geno's.

Can't help you there. No experience with non-Cummins t-stats.

 

[BillBaker]

That's good to know..It sounds like that's what I need to get!....

 

[BigPapa]

My truck can sit and idle for an hour at 50* ambient and not get much over 140*. I'd go drive it and put it under a load. I've also found pulling it up a good steep incline can help burp any air that may be trapped.

 

[Bob4x4]

After the fact.......... You could have filled the system while the t/stat was out.Install the t/stat then top the system.Very little risk of any trapped air.A road test would have been safe and maybe a quart at most to top off.The 12valves are slow to warm-5-10 milesis normal with no load

 

[BillBaker]

Ok so I went out this morning and just turned the key to the on position. The temp gauge jumped right up to that 140 degree mark. Bad sensor?... but how, it was fine beforehand

 

[BigPapa]

Isn't the minimum reading on your gauge 140*?

 

[BillBaker]

Almost.. a slight jump from standstill to 140 degree mark... all has been resolved, ordered a cummins t-stat for a large price of $39. Thanks for all the input.

 

[GAmes]

After the fact.......... You could have filled the system while the t/stat was out.Install the t/stat then top the system.

There isn't any need for any of that with a 12 valve. The jiggle pin (has the little hose attached to it) bleeds air from the engine when it is not running. It's in the FSM . So after a few starts and stops all air is purged.

 

[BillBaker]

Yes...I'm just finding all this out now in reference to the OEM Cummins t-stat having jiggle pins and other aftermarket one's not.

 

[GAmes]

You misunderstand. The jiggle pin is a separate item, it is not incorporated into the t-stat. The little curved hose is attached to it on one end, the other end bypasses the t-stat housing and exits the air into the upper radiator hose fitting.

 

[BillBaker]

Can you provide a reference picture of this jiggle pin?

 

[GAmes]

Look on the top of your engine. You will see a small 6 inch long hose. One end is fitted over the top of the jiggle pin (fsm name) the other to a fitting on the front of the upper radiator hose connection. Cummins quickserve (You have subscribed to it, correct?) lists it as a check valve PN 3926761
https://quickserve.cummins.com/qs3/...ail.html?path=/qs3/parts/99/t/08.07/th9026-01

 

[BillBaker]

Thanks much, no I was not aware of that site.

 

[savage54]

Look on the top of your engine. You will see a small 6 inch long hose. One end is fitted over the top of the jiggle pin (fsm name) the other to a fitting on the front of the upper radiator hose connection. Cummins quickserve (You have subscribed to it, correct?) lists it as a check valve PN 3926761
https://quickserve.cummins.com/qs3/...ail.html?path=/qs3/parts/99/t/08.07/th9026-01

Hey, I tried that site and it show's up as log in and pass word. Do you have to join? and if you do how do I do that it does not give me that option.