93deluxe

Hello All, I registered here a while back, just never posted until now.

Over the summer, I purchased a '93 Deluxe 4x4 22RE 5spd. I have had no cooling issues until the ambient temp was low enough to require heat in the am. That's when I noticed the temp overshooting. My first thoughts were T-stat sticking, after replacing it three times with an OEM Toyota 88deg.C to no avail,I started searching.
After extensive research and trials, I still have not corrected this issue.
My research includes many threads on this issue including the Toyota TSB (#029032787) and Roger's article found here,
http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

I started with completely flushing the cooling system with SolderSeal coolant flush, I removed the freeze plugs after running the flush to check for sediment in the engine block. Clean as a whistle. New radiator, water pump, new dual valve T-stat part# 90916-03070 and refilled with 50/50 distilled water and oem Toyota "red" coolant.

With the heat on, the temp still overshoots in the am.
The colder the ambient temp, the worse the overshoot.
Any Ideas???

84sr5yoty

Check for any pinholes in ALL related coolant hoses.

Did you replace the radiator cap or just transfer the old cap to the new radiator?

Did you angle the truck facing up hill and burp the cooling system of all possible air with the radiator cap off?

DeathCougar

iTrader: (23)

I am a little confused....define "overshoots in the AM"

Does that mean it gets too hot? And it only happens in the AM? Then it cools down or...?

Does it happen when you drive, or only at idle?

If it only happens while not moving (ie no air flow), or when warming up in the AM, i would look to the fan clutch.

93deluxe

All hoses good.

New cap.

With all hoses connected to the radiator, I filled the engine with coolant via the intake manifold (where the thermostat goes). I then installed the thermostat and housing and topped off the radiator, thus nearly eliminating the possibility of air being trapped. However, just for the sake of argument, I did everything possible to eliminate air being trapped in the cooling system, ie. burping, purging, allwoing to reach full operating temp then cool and recheck coolant etc.etc. [/QUOTE]


The article found here http://www.4crawler.com/4x4/CheapTri...tml#Thermostat describes the issue a little better than I can, but I'll give you a quick run down.
Not strictly in the AM. but anytime the engine has cooled completely to ambient temp.; Upon initial warm-up with the heat on, the temp will rise to well above normal before the thermostat opens bringing the temp back to norm. With the heater control in the cool position, this does not occur.

Basically, yes. The temp coolant temp gets to approx. 215-220deg. F before the thermostat opens. Then the cold coolant from the radiator gets dumped into the engine bringing the temp down to below normal. Then the temp will slowly rise back to normal and stay there.

Either driving or idling. Makes no difference.

Fan clutch is good. It's OEM Toyota and works perfectly as per Toyota FSM.[/QUOTE]

Toyota released a TSB a while back addressing this issue.
TSB (#029032787). This TSB describes '84 22RE trucks and "84-"85 22RE Celicas as being the only affected vehicles. The dual valve thermostat part#90916-03070 was the Toyota authorized repair for this concern..
Although my truck does not fall under the described vehicles for this TSB, there are many people who have had this issue with many different year model 22RE powered Toyotas and this dual valve thermostat fixed their concern.
It has only helped with mine. With an OEM single valve thermostat, my temp would rise to the begining of the red before coming back to normal. With this dual valve thermostat, the temp goes just past half way, which measured with a pyrometer, is about 215-220deg. F.
Also noted is the temp gauge stays consistently higher on the scale the entire time the heater control is in the warm/hot position. Only by a minimal amount though, not enough to cause concern.

4Crawler

iTrader: (3)

You might also try drilling the 1/16" hole in the t-stat flange. That helps with many folks. Also, check your cooling system for air pockets. I find if I fill mine with the front of the truck uphill, heater valve open and run it until hot like that, I get a good, air-free coolant fill. I've had zero issues to temperature gauge overshoot since installing my dual valve t-stat and that was almost 9 years ago (still on the same t-stat even). And my temp. gauge used to spike every time the engine was started cold and the heater was on.

93deluxe

I know this works with a 1/8" hole in a single valve t-stat, however, as you stated, that is what the smaller valve in the dual valve t-stat is for. It opens at a cooler temp allowing coolant to pass through, thus eliminating temp overshoot. It just didn't eliminate the spike in mine. It only lessened it.
I was hoping there was something else cause when you drill one it takes a long time for the engine to reach full operating temp.
I have been looking into re-routing the heater outlet hose, possibly directly into the radiator. I'm not sure how its plumbed on the earlier model, on mine the return hose is connected to the intake manifold directly beneath the coolant temp sensor, which is not on the same intake runner as the thermostat. Thus leading me to believe that the "cooled" coolant from the heater core should not affect the thermostat. It seems to me that the gauge should read the temp of the coolant coming out of the heater core. But it's definately got me puzzled.

4Crawler

iTrader: (3)

The size of the hole most folks say works the best is 1/16", not 1/8". Might also be worth testing the t-stat in a pot of hot water on the stove. See what temperature the valves open at and how far they open.

longhungsilver

I have the same issue, im thinking a dual tstat will probably fix it but why bother?? I figure theres not much harm, it doesnt get scary hot when it overshoots, truck runs a bit rough while its above normal temp then boom back to normal everythings fine

4Crawler

iTrader: (3)

Yes, don't think there is any harm to the engine. I mainly wanted to fix mine because I do look at the temperature gauge periodically and if I see it rising above normal, I figure something is wrong. Having false readings from time to time is bothersome and you start to not trust gauge. Having a gauge and ignoring or not using it make the gauge sort of pointless.

ernest t bass

AIR BUBBLES - I ended up replacing the fan clutch and radiator when all i had was an air bubble, my stupid paranoid 3.0 ass.

longhungsilver

despite the cold today i tested it and had my heat selector all the way on cold and still the temp gauge crept above normal for a minute.. anyone else have this happen on hot and cold setting?

mikeaspen

I really learned a lot on this forum and it helped me resolved a cooling problem the has persisted for a year. It started with the purchase of a 1995 4Runner that I set up for off road hunting in the rough and rocky outback of Nevada. It made it thru the first season, 2014, then the rotten and plugged up radiator quit working in Oct. 2015 on the second year of elk hunting. The new Napa thermostat got so hot it bent the center post. I towed it home then changed out the radiator (local rad shop), water pump (Napa), radiator cap (Napa), thermostat (Napa), hoses, clamps, belts (all Napa), and went ahead and did the starter and alternator and internal timing chain. So you'd think everything would be fine, right. Well, during test drives in the steep hills behind my house it kept blowing the cap off the overflow reservoir and then blowing steam everywhere. So I switched out the $6.00 Napa thermostat to a $34 Toyota thermostat and that helped a little with the gauge needle staying in the middle but it would still reach a point and blow out all the water while climbing steep hills. I then surmised that the $5 radiator cap from Napa (13 lbs.) was letting hot water blow by it and into the reservoir thus emptying the engine and radiator of coolant. So back to Toyota again to get a $24 radiator cap and BAM, problem solved. I can drive it on a hot August day and climb steep hills and have no problems. Lesson learned, buy Toyota brand products for the thermostat and radiator cap. While reading all the different forums here I had picked up stories of doing this and I should have done the trip to Toyota earlier and it would have saved me a lot of time and overheating my little 22RE engine. I'm hoping I didn't damage the head gasket.

chuckross1957

New record for old post resurrection?