Thermostat question

[btoscano]

Hey all,



I changed out the factory original upper and lower radiator hoses and the existing thermostat. The thermostat was not cycling, but I figured while I was flushing the coolant, might as well.



The old thermostat had the casing around it. Those that have the Cummins engine shop manual from 1994 it will picture is as the "new" and the ones without the casing are "old".



Cummins CalPacific in Ventura sold me Cummins PN 3802968 - without the casing for use in my 1993 Dodge W250.



I checked a previous invoice from 2004 back when I had my 1990 Dodge D250 and I was sold Cummins PN 3917324 by Cummins Cumberland in Nashville - cannot recall if it has the casing or not.



Which is the correct part number?



Does it matter?



I believe the original thermostat in the 1993 Dodge W250 was not a Cummins part. The engine seems to run a few needle widths higher with the new Cummins thermostat 3902968. This is why I ask.



Thanks,

 

[bgilbert]

3802968 is what I bought a couple years ago, it came with the rubber 'doughnut' looking gasket. I assume this is what you are calling the 'casing'? Did you reuse the old gasket, since you didn't get a new one? I don't know if it matters or if it will leak without it. There are a bunch of Cummins t-stats. 3917324 could just be an updated part number. Definately don't want to use a Napa or other chain store stat.

 

[Headshot zod]

Is this based on the housing? There is a cummins tool ebay that I think is for that thingee.





http://cgi.ebay.com/ebaymotors/Ther...ameZWDVWQQrdZ1QQcmdZViewItem#ebayphotohosting

 

[btoscano]

The casing/cover around the thermostat so its not "open" like most thermostats. The Cummins thermostats come with (a) the thermostat, (b) the donut gasket and (c) the blue "THIS IS NOT A GASKET" thing that remains a mystery.



I don't think the 391 part number is updated because the 390 part number is date stamped AFTER I bought the 391 part.

 

[BBliss]

the this is not a gasket is a template to hold up to the casting hole in the head. some heads had left over material in the casting of the thermostat cavity. when installing the new thermostat hold up the blue template to make sure there isn't any metal intruding into the area where the new therm will go. if it is then this will have to dremeled out before installing new thermostat.

 

[sdstriper]

I bought the thermostat kit with the template, part number 302968 about three months ago.



There was a TSB 07-01-91 for engines with a serial number before 44465181. It addresses the possible problem with the head casting where the thermostat installs on engines built before serial number 44465181. If the TSB was addressed at a dealership it should have a letter stamp on the head, "G" or "M", on the head over the timing gear cover. Straight up from the engine ID tag.



Mine was not stamped, curious if anyones is?

 

[sdstriper]

I should add that the "G" stamping shows it was inspected and your ok and the "M" would show milling was required.

 

[bgilbert]

I should add that the "G" stamping shows it was inspected and your ok and the "M" would show milling was required.

I never had a problem when installing that t-stat. I have an early engine with serial number before that. I'll have to check my old cylinder head for a G or M. When I installed this new style cyl head, I reused my old 3802968 t-stat. I'll have to check it too.



What was the possible problem? T-stat not fit?

 

[sdstriper]

What was the possible problem? T-stat not fit?

I'll qoute the TSB. "Some vehicles may exhibit an overheating or no heat condition. Interference between the thermostat and the cylinder head coolant passage opening on engines built before the engine serial number 44465181 may result in the thermostat sticking in the open or closed position. "

 

[btoscano]

Hey all,



The "correct" thermostat part number for our trucks is 3917324.



3917324 is what I put in my 1990 D250 to correct the windshield-wipers action of the temp gauge. I sold that truck and now have a 1993 W250. For the W250 I installed a new thermostat when I flushed the coolant. The dealer gave me a 3902968 thermostat and it doesn't work as well as the thermostat I removed. I will replace it with 3917324.



Cummins specifies the 3917324 part for 6BT5. 9 engines with Chrysler options.



Hope this helps someone,