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?

When you say fail, how do you mean fail? Is your temp fluctuating or just cold or just hot? The reason I ask is that I have been fighting tstats for quite a while. Makes no differance which brand I have tried.

Takes longer than normal to warm up except on hot days, and fluctuating temps. If i leave it idling, the temp gauge will drop to the next mark below 190.

I am on my 7 tstat in 5 years with none of them giving me a good temp. Mine fluctuates between 160 and 180. I have had the following"2 from napa(one I believe turned out to be for an 03 cummins by the part # on it) Pretty sure it came from them. I was not trying to keep score then. 1 180 cummins which ran much colder2 stants from differant vendors1 from o'rielly's than ran hotter than the others but still fluctuated. it just went cold on me the other day1 from car quest. I just put this one in with the same results.I cant help but believe there is something else wrong, but have not been able to figure it out. I dont beieive for a minute it is the tstat. There is no way I bought that many and differant tstats with the same results for it to be a bad tstat. I have not seen anyone else here that has the problem other than you and me. I have seen other people with the same problems elsewher, but have yet seen anyone with a solution. So if you can find the answer it will be valuable info for alot of folks.Ther is something wrong somewhere, but Icant find it.

I thought you had posted before about going through thermostats. I've got to put mine in the shop for a heat/ac issue and I'm going to ask them about that. I'm with you thought, having a hard time believing that there that many defective thermostats out there.

I will be interested in what if anything they can find out. I have faith the problem can be remedied.

Napa has the best thermostats. I get mine there and they are rock solid. Is your coolant level good?

I will be interested in what if anything they can find out. I have faith the problem can be remedied.

I have a solution!

DON'T BUY CHINESE!

I saved ALL of my receipts from the recent service work I done, cause most of it was, "Made in China".

I'm not going to be shocked when I have to replace something soon....

I think I'm going to try a Cummins this time. Yes it's good, had it changed out with the heater core and ac evaporator in March of this year.

Have either of you replaced the water pump? I ran a bosch from pep boys for a few weeks and it fluctuated from 190-220 constantly and it alos had a little ring tacked to the impeller, which my stocker did not have. I got one from napa without the ring and it works great.

Napa has the best thermostats. I get mine there and they are rock solid. Is your coolant level good?

Those are the ones I typically run.

I just put one from O'Reilly's and it works just fine.

If yall look at the list I posted I have tried every brand yall have mentioned with basically the same results. over cooling. The one that is in now came from Car Quest and is made in the USA. I installed a new water pump 6 monts ago. coolant level is full. I have seen alot of other folks with this problem and I cant seem to find what the problem is. It is definately not the tstat. There is no way I have bought 7 bad tstats of differant brands. But if anyone has had the same problem and fixed it with something besides a tstat I am all ears.

it was time to do a complete coolant flush..so two months ago i did that.newupper and lower radiator hoses..new water pump..and new tstat..190 degree stat.hoses and water pump came from genos..all gates stuff..very happy..installed new 16 p.s.i. cap..and the temp flucatated more than with the factory 15p.s.i...so i left the 15 on..have been told buy different cummins shop foremans at different cummins houses and in different states to see if i would get a different answer..they all said to stay with the 190 degree.

I'm also running a new water pump and radiator cap. For instance yesterday, it was 92 with 50% humidity and drove 7 miles and it still hadn't hit the 190 degree mark so I'm pretty sure I've trashed another thermostat.

maybe an air bubble?

I have refilled this thing 2 or 3 differant ways with the same results. I just change the tstat and the radiator is full to the cap and the block was full to the tstat. The upper hose appeared to be full also.

I burped both heater hoses couple of times each and the thermostat I have has the little swivel thing on it.

My swinging temps are back, 190-226 and back down pretty fast but its staying around 200 for the most part. It seems like I get one thing fixed and another rises the next trip. I just put a big line kit on and a steering box brace, just got the injector lines to qquit weeping and now my temps are all over the place.

Sounds like a thermostat change is in order...

Im gonna do it first thing in the morning. Thing is, its a new 190 from napa but im gonna try the old one I pulled out and maybe the new 180 from cummins just to see if it swings with it.