After getting back from our 5000+ mile trailer hauling holiday, I noticed the temp gauge is now droppng in temp at red lights and when idling. Is this normal? It seems to me it always maintained a steady 90-95C in the past.

 

Depends on how much it's dropping. The stat could be sticking open a bit. I replaced mine recently to resolve my spikey temps. Took about 5min to replace.

 

...any particular brand of thermostat?

 

Don't get a cheap one. Get one from a Cummins shop, about $30.00.

 

You get what ya pay for!!..
Always get the best and it will last longer and less troubles

 

Do I have to drain the rad at all?

 

You have to drain a little bit, I forget how much. Maybe half a gallon. Just enough that it doesnt come out the stat when you take it out. I bought whatever one was at the parts store, wish I would have considered getting it from Cummins. Hopefully it holds out for me. In any case, they are super easy to replace.

 

okay.., Thanks. Much appreciated.

monday morn: Just called Frieghtliner and he ordered one from Cummins (we don't have a Cummins dealer here in town) They need the engine serial # here's the part # for the 05 5.9 #3954830, cost $36.20 CDN.