Where to buy a Robert Shaw T-Stat

My 99 XJ runs dead on 210* all the time with 96K on it and i would like it to run alittle cooler so I want to add a Robert Shaw t-stat. I ran one on my previous XJ and had great results but now i go to buy one at AutoZone where i bought the last one and the guy tells me they don't carry them anymore?? Autozone's high quality T-stat is a now a Fail-Safe made by MotoRad for $11.99.

Anyone had any experience with Fail-Safe t-stats? Comparison to Robert Shaw?

Thanks
Lincoln

www.flowkooler.com sells Shaw t-stats.

210* is the designed temperature for the older 4.0Ls, not sure about the newer ones. Did you know that engines run more efficiently at 210* than 190?
Jeep on!
--Pete

Pete M said:

210* is the designed temperature for the older 4.0Ls, not sure about the newer ones. Did you know that engines run more efficiently at 210* than 190?
Jeep on!
--Pete

Click to expand...

if thats the case then maybe i should just let it be.........what do you guys think??

thanks
lincoln

i ran the Robert-Shaw and the factory 195* t-stats,both registered 210 on the guage.
Factory stat was about $5 cheaper and came with the gasket.one is in the tool box(robert-shaw).
Wayne

195* is best for emissions, 180* is best for performance.
The factory designed the 4.0 to run between 195-220*F with fuel economy & emissions in mind.

So how does a cooler T-stat equal more performance?
Jeep on!
--Pete

I was overheating this summer and thought I had a bad t-stat. So I went to Autozone and bought this failsafe t-stat. Installed it and it seemed to fix the problem. Now that winter is here I had no heat at all. Temp gauge never got over 1/4 the way up. When it was warm enough outside i opened it up again and found that the over the summer the t-stat had opened up and locked open to prevent an overheat (like its designed to do). The problem ended up being the fan clutch but I replaced the failsafe t-stat with a regular style. Maybe its just me but i dont like the idea of it locking open when it goes to failsafe. It fools you into thinking everything is ok in the sumer.

JD

If they are going to have something like that failsafe thingamajiggy it ought to have a pop up button like a oven baked chicken that pops when done....

Pete M said:

So how does a cooler T-stat equal more performance?
Jeep on!
--Pete

Click to expand...

If the engine is kept cooler, the PCM can run more timing advance so the engine will produce better performance. If the engine runs hot, the PCM backs down the timing to prevent detonation and performance is lost.

Dr. Dyno said:

If the engine is kept cooler, the PCM can run more timing advance so the engine will produce better performance. If the engine runs hot, the PCM backs down the timing to prevent detonation and performance is lost.

Click to expand...

Ok, well that certainly sounds logical enough. Now the next question, will the Jeep computer actually do that? And there has to be a logical limit in both directions, right? Somehow running the engine at 140* can't possibly be better than 200*, can it? (neither of those temps refers to a t-stat, but actual temps of the engine) And then of course the next question is, How much of a difference are we talking about? Is this theory purely hypothetical? Or would there be real world differences? To me it sounds sorta like a lot of the "gains" advertised to be had be mufflers and air filters. Yeah, that 800 horsepower Hemi could see an extra 50 horses at 7500 rpm with X brand muffler, but would my tired 4.0 even notice? And if the timing is advanced, will that engine required higher octane gas? Or will low octane gas simply negate any improvement and somehow result in failure at the sniffer station? Sorry if I'm making this more complex than it should be, but my curiosity has been piqued. :laugh3:
Jeep on!
--Pete

Obviously you don't want the engine to run too cool or the PCM will stay in open loop warm-up mode causing the engine to run too rich with increased fuel consumption and accelerated cylinder wall wear. The transition point from warm-up mode to closed loop is somewhere around 160*F (a hair under the 1/4 mark on the temp. gauge) so a 180* t'stat is safe enough. The PCM can keep the timing slightly more advanced for better performance without the engine pinging, and it'll be more tolerant of low octane gas. A hot running engine is more likely to ping and will need higher octane gas, a richer A/F mixture, or retarded ignition timing to prevent it.
The only problem with the 180* t'stat is that the best emissions are produced at around 195* so if you're worried about the sniffer test, stick to a 195* t'stat. That's why the factory fitted it in the first place.