Hey guys, first time posting to the yotatech site. I've enjoyed going through the search link for my questions, however, I wasn't able to get a handle on this one. My 4runnner (1989 22re, A/T) runs at a temperature that never goes above or below the 1/4 (quarter) mark. I've read posts that suggested this was due to an open thermostat, and that the best option is to replace this with a genuine toyota thermostat (with the grudging acknowledgement that it is significantly more expensive). The one problem I have is that I've read that if, indeed, the engine was running cold that the automatic transmission wouldn't engage into overdrive until reaching proper operating temperature. (not sure of the reasoning, but I'm seem to believe this is something I had read previously). This hasn't been the case and despite running at barely 1/4 temp, my transmission hasn't had any issues switching between all 4 gears, including overdrive. Anyone else have this issue and, if so, did replacing the thermostat help normalize the temperature. I'd rather run cool, but would prefer to do the right fix the first time.
On a side, this is a fantastic forum and one that I know will enable me to keep at least a few more repair dollars in my pocket.
Thanks,
Marc

 

Get a thermal gun and let it cold up, hehe, you should be at aboot 185-190...If your below that well I dont really know why. Welcome to YotaTech.

 

Hmm, ok. Assuming for the sake of argument I'm not running in that 185 range as you suggested, would a replaced thermostat help regulate engine temp so that it operates at a more effective (and normal) rate?

 

a good, properly working thermostat is the answer to your overcooling problems. up there in the frozen wastelands called canada, a thermostat is your best friend. welcome to yotatech

 

The stock thermostat rating is, IIRC, 190-195. Running a colder thermostat won't hurt things much, but if the engine doesn't warm up enough it will not enter closed-loop mode and will run rich because of that.
I have a 180F thermostat in my 91 and it runs, according to the gauge, just below 1/4. with a 190F, it's just above 1/4 maybe slightly below 1/2.
If it's not causing you problems, I wouldn't worry much about it.

One thing to note- fuel economy will be better with the engine running "as hot as possible without experiencing detonation". So as hot as it can be as long as there's no pinging will get you the best mileage.

 

Thanks guys, great feedback. While I suppose there is no real problem, I'll likely replace the thermostat with a OEM from Toyota, opting for a 190 rating. Given the comments it is pretty obvious the previous owner ran a cooler thermo (or that it is simply stuck open) which, as abecedarian noted, could have an impact on my fuel economy. Either way, I'll likely just do some preventative maintenance and replace the hoses with the thermostat while doing a cooling flush (with the new mixture being 50/50).

 

With the 22re you need to go with this dual t-stat part # 90916-03070.: http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

Welcome to YT

 

Thanks Mt.Goat. I bought my t-stat this morning before reading your post. The Toyo dealer gave me 90916-03078, which is the same listing as toyodyi.com. Any reason there is a discrepancy between your part # listing and the one from the service department, (except for the fact that the one you suggested is a two stage t-stat). 4crawler noted that the two-stage t-stat is 35-40 bucks , ouch. It must be significantly better to warrant buying it which, as it happens, I'll have to wait to do

 

you could drill a small hole, not exceeding around 1/8", maybe even start with something a bit (no pun intended) smaller like 1/32" in the frame somewhere around the thermostat and acheive similar results as the two stage. But if you do that, start small and see how it goes before drilling to a larger size.
In the past I've used single-stage thermostats from autozone and not encountered the temperature gauge 'overshoot' problem 4Crawler discusses on his site and the two-stage thermostat is intended to prevent. I am experiencing it on my 91 at the moment though, but bought 180 to put in with the new engine because I didn't know how it was going to run. I'll be switching it out for a 190 when I get back home.
Also, I don't turn my heater on until the engine has warmed up because I know having the heater on will delay the engine warming up since coolant will flow through the heater core even if the engine hasn't warmed up completely, and I don't want cold air blowing on me while I wait for the truck to warm up enough to blow hot air, which is usually within 1 or 2 miles of driving it.
To be honest, the heater design on the 22re leaves a bit to be desired, but it is what it is.

 

Sorry to hear I was too late, well at least if it over-heats with the heater on you'll know why.

 

Well, that's a little harsh.
A single-stage thermostat won't caust it to overheat any more than a dual-stage will. One may just get a little 'spike' in the temp before the thermostat opens.
Even the 91 I mentioned above only raises to about 1/3 of the gauge before dropping to 1/4 with the 180F single-stage. My 88 with a single stage 190 doesn't spike at all even if I happen to forget to turn the heater temp control over to cold.

 

I drill a hole in all stats that don't have one just to bleed air.
Bigblock

 

I has all the same problems befor I put in a new thermostat. solved everything for me. I also got a single stage. I didn't know anything about the two stage. It works just fine. I will have to agree a thermostat is your best friend.

 

Just an update guys. Since posting and getting the feedback, I've replaced the t-stat, and it has done the trick. It wasn't the duel t-stat (though I'll replace with that one next) but the single valve. I run 1/2 now between my white markers most of the time, especially driving down the highway, but get a little bit of variation driving around side streets. Not sure what this is about, but it hasn't gone below 1/4 or above 3/4 so I only guess that's "the norm" (for the Toyota heating system anyway). The fluctuations are there, though subtle, and perhaps this is a good indication of a properly functioning t-stat (moving around as opposed to running cold and staying stuck at 1/4 which was the previous problem). Also, I don't think I added enough anti-freeze to my water mixture, so I'll likely drain that tomorrow to ensure that I have a 60/40 mix, and perhaps that will be the cherry on top. Ever get that feeling that you know that you've done something right, but you're just waiting for the bottom to fall out If I make it through the weekend I'll assume I did everything correctly

 

just wondering, would a 2stage thermo heat up quicker? or no?

 

From my understanding 4 crawler http://www.4crawler.com/4x4/CheapTri...tml#Thermostat suggests that it helps regulate temperature better and helps prevent heat spikes which some have suggested are common on start ups. Not sure if the 2 stage heats up any faster.

 

hmm yeah thats what i was thinking to.. i cant stand the cold lol...

 

Interesting you say that. I had an Autozone/Stant thermostat in my truck before my rebuild and I never experienced any 'overshoot' problems. Now, since I am using an OEM thermostat, I get it every morning. Very strange