Which thermostat?

[Mikey von]

I have searched and there is a lot of conflicting information.

I have the high output serpentine water pump and the stock single thermostat crossover. I want the 195 degree. Which thermostat should I use on my 6.2L?

Part #?

Is it the RS 354? Hopefully something from either Napa (local) or Summit (will be placing a large order) to save on having to pay extra shipping.

thanks!

 

[okieraptor]

I think everyone uses the 180. Sorry I don't know the part # though.

 

[Mikey von]

195 is the proper temp from what i understand and the engine runs more efficient there. Folks run 180's to try and band-aid a week/ poorly designed cooling system.

 

[Mikey von]

Would this be the correct stat - it has the spring loaded by-pass valve.

 

[longbedder]

195 is the proper temp from what i understand and the engine runs more efficient there. Folks run 180's to try and band-aid a week/ poorly designed cooling system

The thermostat will not compensate for an under-effective cooling system. If you have serious cooling issues, it will be with your 'stat wide open regardless of it's designated temperature rating. Put another way, you could run a 160 or a 195 in a "weak/poorly designed cooling system" and the problem would be the same with either stat stuck wide open - you'd be overheating. All the stat temp rating does is determine the lower threshold of when the stat opens - once it's open sustained and max temps are up to the water passage, pump, and radiator designs.

You won't see much mileage (call it overall efficiency) difference if any between a 180 and 195 stat in a 6.2l diesel. Your IP is mechanically set and will deliver the same dose of fuel from squirt to squirt regardless of the cylinder temp. You could monkey around with it if you had some sophisticated sniffer equipment to try and obtain max efficiency, but in reality you'll probably just turn the IP up until the EGTs max out around 1100 degrees under load. On a computer controlled fuel injected vehicle you could notice a small difference as the fuel delivery is controlled by a feedback loop. The automakers also like to get the temp up in order to get the catalytic converter (which you don't have) nice and hot.

In terms of mechanical devices, cooler operating temperatures translate to longer life. Oils also lubricate better by retaining greater viscosity at lower temperatures. You also have a fluid-to-fluid transmission cooler integral to your radiator - the lower the antifreeze temp the lower your trans temp will be.

 

[Mikey von]

The thermostat will not compensate for an under-effective cooling system. If you have serious cooling issues, it will be with your 'stat wide open regardless of it's designated temperature rating. Put another way, you could run a 160 or a 195 in a "weak/poorly designed cooling system" and the problem would be the same with either stat stuck wide open - you'd be overheating. All the stat temp rating does is determine the lower threshold of when the stat opens - once it's open sustained and max temps are up to the water passage, pump, and radiator designs.

Agreed! I believe 195 is the OEM temp. You will see threads on the 6.x diesel forums about overheating and many say switch to a lower temp (180) stat. I agree that if the cooling system overheats with a 195 stat it would do the same at 180. That is why I called it a band-aid, perhaps poor word choice?

You won't see much mileage (call it overall efficiency) difference if any between a 180 and 195 stat in a 6.2l diesel. Your IP is mechanically set and will deliver the same dose of fuel from squirt to squirt regardless of the cylinder temp. You could monkey around with it if you had some sophisticated sniffer equipment to try and obtain max efficiency, but in reality you'll probably just turn the IP up until the EGTs max out around 1100 degrees under load. On a computer controlled fuel injected vehicle you could notice a small difference as the fuel delivery is controlled by a feedback loop. The automakers also like to get the temp up in order to get the catalytic converter (which you don't have) nice and hot.

I am sure you are correct and for my intent 180 or 195 is not a big deal, but getting a quality stat (Robert Shaw?) with the correct by-pass valve (or no by-pass) is what I am looking for.

 

[MaxPF]

First of all, only use an honest-to-goodness AC Delco t-stat. Aftermarket stats are really hit-or-miss in my experience

Post up a pic of your stat crossover and I can tell you what you need.

Also, here's a little piece of info for those who want an OEM-quality 180° stat for the non-bypass blocking 6.2 housings: The t-stat for the '89-98 B series Cummins is a 180° unit and drops right in. It has a bypass block disc on it, but it's too short to work in the 6.5 bypass-blocking housings. That shortness means it easily fits in the non-BB housings without interference though Just make sure you get it from Cummins or Dodge, otherwise it will probably be some aftermarket POS...

 

[AJMBLAZER]

Rock-Auto sells the ACDelco thermostats and GM dealers can still get them fwiw. I got two from RA last time I bought from them. I wasn't impressed with the NAPA part.

 

[Mikey von]

I think the t-stat crossover that I have on there and plan on using will not work with the '94 serp setup. The outlet interferes with the alt/idler pulley bracket. I am guessing I need the single stat crossover from a serp setup 6.x.

 

[MaxPF]

Probably. The one you have on there is the non-bypass blocking stat housing. The one you probably need is the bypass-blocking housing.

Either way, tell the GM parts guy you want the stat for a '95 6.5 diesel pickup. It should have the blocking disc like the one you posted a pic of above. It will also have a rubber outer around it. If you use it in the bypass-blocking housing, just run it as-is.

to use it in a NON-BYPASS Blocking housing, like the one you have pictured above, you need to remove the circlip that holds the disc, remove the disc and the spring, and cut off the little brass rod that held it all. Then you can run it in the non-blocking housing without issues. This is worth the effort because the AC stats have been far more reliable than any aftermarket jobbie in my experience.

 

[Mikey von]

Probably. The one you have on there is the non-bypass blocking stat housing. The one you probably need is the bypass-blocking housing.

Either way, tell the GM parts guy you want the stat for a '95 6.5 diesel pickup. It should have the blocking disc like the one you posted a pic of above. It will also have a rubber outer around it. If you use it in the bypass-blocking housing, just run it as-is.

to use it in a NON-BYPASS Blocking housing, like the one you have pictured above, you need to remove the circlip that holds the disc, remove the disc and the spring, and cut off the little brass rod that held it all. Then you can run it in the non-blocking housing without issues. This is worth the effort because the AC stats have been far more reliable than any aftermarket jobbie in my experience.

I will be looking for a newer bypass blocking housing as the one on there now interferes with the accessories and brackets.