Hello all,

1986 2WD base model 22R carburetted pickup.....91K miles now......great running truck. Over the past month, I have noticed that occasionally the temperature gauge does not read any temperature at all, sometimes during the whole drive and sometimes just for a short time and then comes to life. This has only happened 3 times, with today being the 4th.

There are no other symptoms. Coolant levels are correct (new coolant last year and flushed the whole system and block).

Any thoughts? Bad sensor; bad gauge? The intermittent (very intermittent) nature is strange.

Thanks,
Julian

 

thermostat upside down?

 

Thanks for the reply, but no. I've had the truck for 6 years/40K miles now, and no issues before now, so the tstat must be in the right way around. Fine this morning!!

Julian

 

I'd start with the gauge temp sensor, the connection, and then the wiring.

 

Hi guys,

With work and weather, I have not had time to look into this. Same issue....... on occasion it happens (ie. driving to work yesterday it did; driving back home 10 hours later it did not!). But, the symptom I did forget to mention is that the heater blows fairly cold when the gauge is not registering (not talking upon startup.....after driving for 20 minutes and still nothing registering on the gauge). Perhaps the thermostat?? I have not heard of one that fails occasionally. Any thoughts??? If so, how difficult is it to change on the 22R? Most of my other cars I have replaced it, and it has been good access and simple (except my Hillman Imp.....buried behind the engine.....not fun).

Thanks,
Julian

 

The tsat in the 22R/22RE is super easy to get to. It's on top. right between the throttle body and the valve cover. On the far end of the upper radiator hose, where it goes into the engine. You may need to move some vacuum lines out of the way when you go to install the 90° aluminum piece it's inside of, during reassembly. Just follow the upper radiator hose to where it hits the 90°. You'll need to drain out some coolant to open it withoutt making a mess. Maybe 2 qts. There are 2, 12mm head size bolts holding it down, and a rubber gasket around the rim of the tstat. The torque value isn't all that high on them when you go to reinstall it. You don't even need to pull the upper radiator hose off it, but it makes it easier if you do. Make sure you don't leave any coolant in the 2 bolt holes, or you'll get corrosion in them. Same with the shelf the rubber gasket sits on. Make sure all that is clean and dry when you go to reassemble it all.
Just pull the two bolts out, lift out the thermostat, and voila! Quite often, you can just peel the rubber gasket off the old tstat, and put it on the new one. IMHO, a new gasket is a good idea though. Put it down into the hole, making sure the jiggle valve is orient correctly. Exactly where the original was.
Quick side note: there is an upgraded version of the thermostat. It has a small "sub-valve", that looks just like a mini-me version of the big thermostat where the jiggle valve goes, replacing the jiggle valve. It came about because, with regular setup, the Toyota system tended to warm up until the engine was up to 3/4 or slightly more, then drop down to the usual running point of 3/8 or so. It's due to the return from the heater system returning to the system just before the thermostat. The "cool" water from the heater return holds the thermostat closed until the overall temperature gets to the high point before it opens.The "little" thermostat opens at a lower temp than the main one, allowing the engine to run at it's normal temp, until it get's enough hot water from the main circulation portion to open the "big" thermostat. After that, the whole thing funcionss normally.
Anywho, once you have the new tstat in, torque the bolts properly, put the coolant you removed back in and make sure the recovery tank is properly filled. It's a good idea to "burp" the system at this point. After running the truck for 1/2 hour or so, with the heater on it's highest setting, with the radiator cap as the highest point by parking the truck on an up-hill, or on ramps or whatever, shut it down, and let it cool for 20 to 30 minutes. Top up the recovery tank as needed, and most likely it will be needed, and drive it as normal. Check the recovery tank again the next day, and you'll be GTG!

Hope this some, small help...
Pat☺

 

Hello Pat,

That was a massive help.....thanks for taking the time! Just tweaked my back a little, so might have to look into this the end of next week. What is your opinion about my diagnosis of the tstat being at fault relative to the symptoms I described? Also, I am sure a standard tstat is easy to get, but who supplies the upgraded one??

Thanks!
Julian

 

With no heat now on the table that changes things.
If there hasn't been any loss of coolant than the thermostat would be first to remove and test/replace.
Once you remove it plan on replacing regardless. Testing it and seeing it fail just confirms your thoughts.
The best thermostat to get is a genuine oem Toyota thermostat. Hands down.

 

Ive messed around with my thermostat extensively, so figured I'd chime in...Toyota sells both models of thermostat, the normal one and the one for trucks with the heat spike problem. As an amateur, I've had best luck using the funnel style radiator burp kits, and burnt up an alternator once by letting the fan blow coolant all over everything after the radiator overflowed when burping without the kit.

 

Julian: Could well be that it's stuck, or sticking, full open, instead of partially open, to control the temp properly. It happens. It will eventually wind up full open all the time, as a safety feature. Better to be too cool than too hot! Do NOT remove the tstat. The water will flow through the radiator too fast, and it will overheat. No time to cool down.

OldBlue: the funnel version is good, no question. Having said that, parking it on a hill, and opening the radiator cap to the first click, or first detent, will allow the water to flow into the recovery tank, and then the air. It won't permit the water to escape, though. Then once you shut it down, put on a heavy glove and tighten the radiator cap all the way down, and it'll suck the water out of the recovery tank. Keep it full to the fill line, and you'll be gtg. That's my method. I changed a ton of tstats, living in Yuma, AZ almost 30 years. 110° F on average is hard on them. Even a few fan clutches.

Well, like I said, that's just my way. YMMV
Have fun all!
Pat☺

 

Thanks again......I too thought the tstat might be stuck sometimes.

I will order a genuine one. It appears Rock Auto has them (AISIN) for a bit less and so does Amazon (TOYOTA) for a bit more.

More Information for AISIN THT002


Also looks like I will need a gasket and sealing o ring:

More Information for AISIN THP105
Gates Coolant Thermostat Housing Gasket for 1970-1986 Toyota Pickup 1.9L ih | eBay

Please confirm if you agree with what I have listed.

I have not had issues with air blockages in any of the cooling systems I have worked on. Usually just fill them, run them with the heater on full, drive them, refill, done. I flushed the Toyota's system early last year (removed the plug in the block too behind the alternator area). That said, I invested in a Mishimoto vacuum refill kit that I planned on using on two of my British cars that I've been told are a nightmare to bleed. So I have that as a backup, although yet to use it!

Thanks again all.....always great help here!!

Julian

 

Aisin makes a very good product, but I think the oem thermostat (90916-xxxxx)is made with even heavier gauge material.
you just need the o-ring that goes around the lip of the t-stat. That is the gasket. Make sure the t-stat is sitting properly in that recessed pocket. If it’s cocked to one side it can crack the housing as you tighten

 

Thanks Jimkola. Went with the AISIN as it is a solid name related to Toyota and I could get both the gasket and tstat from rock auto. Will update this once I get it, replace it, and test it!!!

Thanks,
Julian

 

Great, hope it works out.

 

Realized, when posting something else, that I did not post the outcome! The AISIN tstat worked perfectly. Temperature registers properly on the gauge and heat is back.

Thanks all!
Julian