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Lower temp thermostat

Shran

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The application I found a 180 degree stat helpful for was low speed rock crawling. My 302 will sit and idle all day long at 195 with a 195 stat, it doesn't necessarily overheat nor does it use coolant but if you really start working it hard without the air flow you'd normally get on the road, the temp will slowly creep up to 210, 220, 230, etc...so I had to stop and let it idle and cool off for a bit. I rarely have to do that now and it usually idles at 180-185 degrees. Coolant flows through the radiator more often because the thermostat is open for longer periods of time thus it prevents a lot of those temperature increases. It sucks in the winter though, 1st gen heaters are pretty pathetic to begin with and it's pretty much non existent with the thermostat swap!

I don't think the casting sand issue is as big of a deal as it's being made out to be. I currently have two 2.9 powered trucks with well over 200k on the original heads! Plus a dozen others with countless miles on them that didn't fail... EVERY. single. cracked. 2.9 head I've seen can be directly related to another failed component or severe lack of maintenance.

Who here is aware that the Ford 351M/400 heads were "notorious" for cracks and failure too? I know a couple people who were/are really deeply invested into building those engines going back to when they were new. I had a 400 with cracked heads at one point and found that it was pretty common but for the same reasons as our 2.9/4.0s: lack of maintenance was the single biggest cause. Certain Jeep 4.0 engines suffered from that too although they have a stellar reputation overall. Some engines are just simply more sensitive to excessive heat.
 


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I use the 180 thermostat and a 4.0 radiator. The extra degrees make me feel better. I am sure a 195(or is it 192?) would be fine and probably be better long term, but I like the assurance.
 

randypmartin

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Just to be clear...
A lower temp thermostat will NOT cure an over heating problem. All it does is slightly delay a overheating problem. One of the main reasons for the higher thermostat temp is to help the oil burn off moisture that condenses inside during cool down.
Thanks everyone for your input. Super helpful i appreciate it!
 

ford4wd08

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So… here’s my input…

@sgtsandman is correct, improper cleaning out of casting sand was a big problem. @PetroleumJunkie412 noted that and also noted that the European market didn’t have the overheating and head issues that we have with the 2.9, so I’m going to say there was poor quality control here that caused a lot of problems. Throw in poor maintenance and general abuse and it’s no wonder there were so many problems and a bad rep.

Sediment in the cooling system from lack of or improper maintenance is another problem. My first Bronco II, I wanted to flush the radiator and when I opened the drain plug. Well, nothing came out. Unscrewed it completely and still nothing. Poked around in the holes and hit it with the hose a few times and finally got the tiniest drip. Ended up pulling the upper and lower hose and going to town spraying water in everywhere. After generous water useage, water would come out the drain hole. Hosed out the heater core and block as best I could, filled it with coolant flush, ran it, drained, sprayed, filled with water, ran, drained, sprayed, more flush, ran, drained, sprayed, water fill, ran, drained, sprayed, water fill, ran, drained, sprayed and finally wasn’t getting any more junk out. Then the motor ate a valve.

My choptop had been overheated by the previous owner when I got it and cracked a head. I chased the overheating problem for awhile and broke a couple more heads. Turns out a substantial part of my woes was a result of a leaky heater core and someone sealing the heater core box with RTV. Looking back, I’m also suspecting an issue with the block being choked up with casting sand. It might be buried in my shed still. The 2.9 that went in the last time I broke heads never gave a bit of trouble. I flushed it and ran a new water pump with a 180* thermostat and a 4.0 radiator. With a manual transmission, 4.10 gears and 33’s, it ran great and was a solid 18/19 mph around town and low to mid 20’s highway, so I have my doubts that there was any negative effects to my cooling alterations. It didn’t like 35’s though, so it got replaced with a 4.0. Well, a few of them. Haven’t had much luck with those motors either in that.

One thing to note, factory spec for thermostats for the 2.9 was 192*, however most “stock” replacements for it are 195*. I don’t know if there is a 185* or 190* thermostat available for these, but I would definitely be a little more comfortable running slightly colder than slightly hotter.

Overkill on the cooling system is possible. My F-150 is a prime example. Even with a new radiator, water pump, and a flushed cooling system in the winter, it wanted to overheat with the plow on. 180* thermostat, super-wetter and a 50/50 or 40/60 mix of antifreeze/water and tilting the radiator slightly back at the top solved that problem. But without the plow on it runs cold. Even in the summer working it hard.
I'm pretty sure all the 2.8/2.9/4.0's were built in Germany, that is why they got the colonge name...
 

ford4wd08

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I know for a fact sediment caused issues with my original radiator. I added AC back and it began pushing temps up to where I didn't like. I replaced my OEM radiator with a 2 core replacement. It added some capacity and actually pushed the fan further into the shroud. I think both helped with my cooling issues.

I am running a 180 degree stat, but mine is in the lower hose that the early 2.8's used. Basically the same as a 192 - 195 degree stat in upper hose.
 

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I seem to remember something about a cooler thermostat increases upper cylinder wear.
I've probably about 340K on my 1990 2.9L... Engine all original, 195°F t-stat. (well, the ODO I think says around 250K (without going out there to look), but a few years with the speedo disconnected because the cable was too short after my crawl box install, and the fact probably over half the hours on the engine since I got it in 2004 have been in low-range, it's certainly got some time on it).

As the miles accrue, I start to wonder that if & when it does go, it'll be something sudden (like the eaten valve mentioned earlier, or the lifter that collapsed on a buddy's 380K mile 4.0 I6 Jeep while on his way to Arizona).
 

4x4prepper

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I have run various thermostats on my Ford (V-6 and V-8) from 160 to 195 stock. I have found the 180 to be a good compromise on EFI engines, since when I drive mine it is either towing or off road. Though on my 2.9L I went with (2 or 4?) row aluminum radiator the biggest I could fit in there with the A/C. Think I used an Explorer one. If you have an automatic I would surely use an aftermarket cooler and remove the transmission lines from the radiator.

Though for an old beat (2 to 4 bbl) carb 390 in my F-100 I went with a 160 degree thermostat and it did fine.
 

Eddo Rogue

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I have a thermostat collection, settled on the oem motorcraft, I think its 192F. I had the multi core thicker radiator in there, but it actually made things worse. Got a new single core and went back to the oem setup, new parts as needed, burped it good, and now zero cooling issues. The temp gauge does creep up sometimes, but never much.
 

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