Proof of a thermostat gone bad.......

[whiteboyslo]

Thought you guys might like this.......

So, my truck has run warm since......well, as long as I have owned it. Didn't have proof until I installed an aftermarket temp gage (Autometer digital unit with the sensor in the factory overtemp location), but ever since then it's been pretty constant at 205 +/- 5 degrees around town, but running it hard or heading up a grade would get into the teens. Towing light loads would get up into the 220s and even low 230s on grades, so something was clearly wrong.

So, I finally got around to installing a new thermostat today. And, just to prove to myself that all the effort was worth it, I threw them both in a pot of boiling water and got some interesting results.......

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The new one is the one with the black bottom (and yes, it's a Motorcraft). Notice how much larger the gap is between the top of the black piece and the bottom lip of the thermostat versus the old one. Also, the old one creaked and groaned something terrible when opening, and was super quick to close up once removed from the pot whereas the new unit took its time.

So, after installing the new one (following the excellent instructions found here: http://www.oilburners.net/forums/showthread.php?60027-THERMOSTAT-REPLACEMENT-101-Tech-PicTutorial), the real proof would be in the temps. Well, I'm happy to report the temps now hover around 195, going as high as 199 and as low as 193 at idle (thermostat opening and closing). I've only run it around town so far, but the highest I got it was 203 after romping on it real good, and even then it backed off QUICK!

I also replaced the fan clutch with an OE unit since the last one would kick in and out at random times. When it DID kick in, temps would fall QUICK, but there was never any rhyme or reason as to then it would kick in, hence the 230 temps. Didn't get hot enough for it to engage just running around today, but hopefully it'll be a bt more regular when it does get hot enough.

So, yeah. Definitely take the time to change the thermostat if your temps are like mine were. It's not really that bad of a job and is well worth it.

Mike

PS - before anyone asks, I'm pretty sure all parts were original. The truck has low miles and, when I bought it, everything was original down to the hoses and belts.

 

[icanfixall]

Thanks for the pics. Yes, your old one was a ford thermostat but the rubber seal around it has left for the top tank in the radiater. Not to worry bout it either. I noticed the new ford thermostat is a newer desin with that black rubber seal. On mine its a flexiable part that can actually form around the top of the thermostat body creating a better positive seal when its closed. Glad you "tested them in a pan of hot water. Factory shop manual tell us they need to open a minimum of 260 thousands so thats just 10 thousands more than a 1/4 inch. Thats full open at 212 degrees at that measurement. I think I will go and buy one like what you have. The factory one I have in the truck has that seal cut off so I can get more volume of flow. The rubber seal is springy enough that it stays tight till the stat has moved some. Reason for the rubber seal is to make a complete seal so the engine warms up and there is no leakage.

 

[icanfixall]

Thanks Mel for including this in the special section where it will do everyone plenty of good. And Al and I get instant world wide fame once again for knowing. Here ya go Al... Let me pad you on the back.. then you can do the same for me....

 

[kc0stp]

IMO 205 isn't running hot, actually running just a tad cold IF itd stayd there (want it within 5 degrees of 210 normally)

 

[whiteboyslo]

Thanks for the pics. Yes, your old one was a ford thermostat but the rubber seal around it has left for the top tank in the radiater. Not to worry bout it either. I noticed the new ford thermostat is a newer desin with that black rubber seal .

The seal basically crumbled apart during removal and handling of the thermostat. It was there, but by the time I took these pics, I had picked most of it away.

Mike

 

[whiteboyslo]

IMO 205 isn't running hot, actually running just a tad cold IF itd stayd there (want it within 5 degrees of 210 normally)

Yeah, but there's that big 'if' in there. Just got tired of freaking out every time I towed the bikes out to a trackday, which then inevitably freaked out anyone riding with me. So, for everyone's sake, this was a good job to do.

Now to find something heavy to tow and really see how she handles it........

Mike

 

[icanfixall]

Well ya got a supercab.. Find some fat chicks or some big dudes and load er up... Actually just hook up what you normally tow and try the hills around you full well knowing you can stop anytime you want. No need to push the rig because you just have to be there on time...

 

[Can30Diesel]

Figure I'd chime in. I have a stant in my truck now which replaced the factory motorcraft which was stuck open. My truck NEVER overheated before the stant t-stat and I discovered that the stant wasn't cutting it while hauling the trailer up two of the steepest hills in the area. Man oh man did she get hot.

I have a motorcraft going in tomorrow (finally got time) and thanks to this little writeup it makes sense why the aftermarket t-stat was sub par. I might even try the same boil water test before the installation with these two and post them.

 

[Greg5OH]

hmm, im at 205 in factory over temp location. havent had a chance to run it up any hills yet...ill have to check that out.

 

[sle2115]

I've had a stant in mine since I got it...never an issue. Much prefer the design to that of the motorcraft personally.

 

[metalminded]

I've had a stant in mine since I got it...never an issue. Much prefer the design to that of the motorcraft personally.

That is a real contrast to what I have found to be the general consensus. Care to elaborate? I have planned on replacing my thermostat since i picked up my truck and I had originally bought a stant, but after reading opinions here I ordered the motorcraft.

 

[icanfixall]

I've had a stant in mine since I got it...never an issue. Much prefer the design to that of the motorcraft personally.

Well this is the post I was looking for. Way back in 2009 at the rally I was privately told this so I was waiting for this to come out. Why this works here is still an unknown. It goes against convention but if it works then great but I sure wish I had a reason for it working..

 

[idi_econoline]

Installed t-stat from Navistar dealer last year.... in recent months it's indicating much COOLER on the factory gauge. Barely in normal range?

Engine's coming out soon anyway for chuffing exhaust valve. Recently got a Motorcraft t-stat from RockAuto. (about half the price) Easy to replace when engine's on the stand, in my case.

Connecting new Isspro gauges from Conestoga once she's running again

 

[whiteboyslo]

FWIW, my OE gauge never got above the 'M' in NORMAL, even when the temps hit the 230s. Pretty much reinforces how useless that gauge is.

Mike

 

[idi_econoline]

Agreed, Mike. The factory temp gauge has been a fairly reliable rough guide. Since I intend to (finally, after 4 years) work this engine a bit harder once the valve's fixed, looking forward to a real, solid number (set of numbers, actually, with 4 gauges) to work with.

As I've reported sometime back, the engine I got with the van had a small-outlet, gasser thermostat. The gaffes made by the PO are too many to list....