Howdy and Merry Christmas Eve-

I put in a new intake manifold, new temp sensor, and new stat.. The stat is rated @ 160*.. I hated to do this but had no choice because my 180* wouldn't fit in the housing, and the only extras I had were 160*..

here's what's going on: The tranny, on an engine that barely has the stat open, makes a funny sound when in reverse.. It's never done that.. how does that system work anyway? Does the stat opening early start circulating cooler coolant through the aux. tranny cooler, and therefor make the tranny fluid start pumping through at a colder temp? Colder fluid is thicker, right? Could that be the cause of the funny noise?

AND- I have e-fans w/ flexi-lite adjustable controller.. I've always kept it near the lowest setting, and the temp gauge always reads just below the half mark when it comes on.. When I had the fan shroud off during the manifold swap, I went ahead and made sure the probe (through the radiator) was in a good spot, and the line was insulated.. Now, it comes on much sooner- like when the needle is a 1/4 way up on the gauge... what would be 'yall's take on that? The temp sensor and the gauge are independent of each other, meaning they read separately and from different places- was my old sensor more accurate? Would insulating the probes wire create that much better a signal that the fans just come on sooner?

What can I expect from running a 160* stat? The engine goes into closed loop much cooler than 160, but will it eff around with other things too?

 

You are going to annoy the PCM, and it will set a code for "Engine too cold too long"

What kind of 'funny sound' are you hearing??? Does it just whine a bit? Gears grinding? Something equally as unfunny?

Need to put at least a 180 stat in there.......

 

All I know is, a 180 stat is pushing the envelope, let alone a 160. I'm very surprised your are not getting a CEL with a P1281 code. 160 is simply WAY too cold for the engine and tranny to operate at the required optimal temps.

edit: I can't believe it took more than 5 minutes for me to type in my reply! LOL

 

Roger that guys.. The 180* is going to go in there, it was simply that the one I had wouldn't fit.. The kind that was in there had the barrel around the spring, the kind that that is in there now (Stant) has the exposed spring.. The F1 simply has tighter tolerances than the keg..

I ordered new injectors.. When they land, I'll put them on and put a open spring design 180 stant on there- or I may just put a 195 on there..

The tranny only does it for the fisrt few minutes of operation.. this is a reach- but it's the best way I can think to explain the sound: It sounds like a playing card in the spokes of a bicycle wheel, but maybe only the very edge of the card and much faster than I have ever pedaled a bike..

It won't be long until the tranny is overhauled anyway.. The builder I intended on having do it has, uh, payed back his debt to society (in terms of days), and I'm likely going to drop the truck off wiht him late next week.. we'll see..

I don't like using that 160*.. but I liked the idea of NO stat even less.. I don't have a CEL, and I've driven it for about 100 miles.. It runs much, MUCH cooler- but again- it might not be running that cool, it may just be the new sensor is either more (or less) accurate..

 

man, I hate to keep beating on this dog- but I'm having a hard time wrapping my brain around this..

Okay: engine runs, stat opens, coolant flows.. one stat opens at 160 degrees, one opens at 180, and one opens at 195.. engine still runs.. the advantage of a 160 or 180 is that the coolant starts flowing through the radiator sooner, and the 195 later.. check?

If the engine runs long enough, and all three stats are open, would it matter at that point which one is on there? wouldn't the engine still run at a dang similar temperature anyway?

This has only happened to me one time- but I climbed a mountain in my truck in temperatures nearing zero.. the truck didn't complain and the temp stayed about halfway.. Coming down the opposite side, though, the truck basically coasted @ 60~70mph... The stat actually closed.. In 25 years and likely close to half a million miles driven, that has happened only once.. I tell you this tale for a reason:

I bet a 180 or a 160 would not have closed, though the 180 would have been close I'm thinking..

I'm at a loss here to figure this puzzle out...

-once the PCM releases the engine to closed loop, what difference does a colder stat make?

- once an engine has been running any decent amount of time, isn't the engines temperature going to be dependent on the engines cooling capacity more so than when the stat opens? I mean, at some point it will heat up regardless of what temp the stat opened, right?


I ask all of these things because this is what makes sense to me... However- I put that 160 on yesterday, and have driven about 200 miles since- and the trucks temp gauge never broke the quarter mark, whereas it usually registers anywhere from 3/8~1/2.. could this be more to do with a new temperature probe or is that engine REALLY running THAT much cooler?

thanks..

 

Why do you think your thermostat has only ever closed once on your vehicle(s) in 25 years, 1/2 million miles??? That's the only mystery / puzzle I can't figure out.

The thermostat IS what maintains the desired operating temperature. It doesn't just open, and remain open after initial start-up.

It DOES CONSTANTLY open and close as temperatures rise and fall, whether you realize it or not.

The PCM and temp sensor have no control of the cooling process. They monitor the coolant temp and adjust fuel /air, timing, etc. for maximum operating efficiency.

And as others have said, ditch that 160* stat..... I'm really surprised you're not throwing codes left and right with it. Get the 180* or 195*.

Mystery solved.....Merry Christmas

^

 

I meant closed and cold, as if it had just been started. I haven't seen any codes at all. I'm going to swap back tomorrow- its hard to find a stat on Christmas day.

 

Funny how it works that way.


The cooling system is constantly cycling, thereby, maintain a 'consistent' temp within the engine itself. That is controlled by the thermostat. Granted, the thermostat can be overwhelmed, and remain in a constantly open state if the ambient temp is relatively high, (humidity plays a role here as well), and the engine is under a constant, relatively heavy load. (pulling a trailer up a mountain, for instance.) Under those circumstances, you exceed the cooling capacity, and heat builds up, eventually overheating the engine. Bad situation.

But, just the opposite can also happen, running unloaded, DOWN the mountain, your engine is not doing much, if any, work at all. Consequently, it doesn't generate much heat. (though it is still generating some. We don't have cylinder shutdown under no load conditions on ours. ) So, if it is reasonably cool out, the stat will close, and remain so, until the engine warms enough to prompt it to open. Depending on conditions, that could take a bit, but, it will eventually open again. (unless it is REALLY cold out)

Now, a hotter engine (to a point.....) burns more efficiently, and produces less emissions. Running the engine too cold, will both confuse the computer, and also reduce efficiency. Not to mention the effects on internal wear. (the parts, and tolerances are designed around an expected operating temp.) There is some leeway there.... but, the computer becomes the sticking point. (especially on the 98 and later models, they were a bit more picky.) If you get a tune for your truck, such that the computer is EXPECTING a 180 degree stat, a few of the issues go away. Or, are at least 'worked around'. The 160 stat is just too cold though. So, getting that out of there as soon as you can would be a very good plan.