rygill

I just replaced the heater core in my 89 4x4 22re pickup. Now, it's constantly running hot and nearly overheating. I've topped up the coolant and there don't appear to be any leaks.
Any ideas as to why it might overheating?

Thanks for any advice!

jimbo74

did you properly burp the system?

also there is an issue with the 22r and re about crap thermostats...

i have had the problems listed above, and it ultimately was a bad t-stat and led to a cracked head/blown head gasket.....

since the HG replacemnt and a different head, I have been running a dual stage thermostat and have had no problems since

look on www.4crawler.com and use its search function to look up dual stage thermostat

rygill

Hmmmm,
Since I don't know what "burping the system" is, I suspect I didn't do it!!
How do I burp the system?

Thanks!!

LittleRedToyota

sometimes a bubble of air can get trapped beneath the t-stat and, so, the t-stat never opens (because it never comes in contact with the hot coolant).

a way to prevent this is to just drill a litte hole (i make 'em 1/8", but some people do 1/16") in the flange of your t-stat (opposite the jiggle valve). that way, if an air buble makes its way to your t-stat, it will pass through the hole instead of getting trapped beneath the t-stat.

the issue i think jim is talking about is called temperature overshoot. it happens because there is no t-stat bypass on the 22RE. a dual stage t-stat or the drilling a hole in the flange trick can help solve that, too.

here is the page on 4crawler's page that jim was referring to that explains temperature overshoot in depth:

http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

rygill

Cool!
Thanks! That sounds like the problem. I was noticing that it was running hotter with the heat cranked...
I'll have a look at it this evening.

LittleRedToyota

if you haven't burped the system after replacing the heater core, i'd say there is a very good chance youhave air in the system.

to burp it:

park the truck facing uphill or jack the front end up (want to make radiator cap the highest point in the cooling system. when sitting level, the heater control valve is the highest point.)

with the engine *cold*, remove the radiator cap. put the heater control on full hot. start the engine. let it get good and hot.

when the t-stat opens and the coolant starts circulating through the radiator, any trapped air bubbles will make their way to the radiator and "burp" out. (sometimes splaching coolant out.)

keep an eye on the coolant level in the radiator, as the air burps out, coolant will be sucked from the radiatory into the engine and you will need to add more coolant to the radiator.

keep doing this until it stops burping out air. shut off the engine, top off the radiator and put the cap back on.

then make sure you have enough coolant in the overflow tank and keep an eye on that for a couple of days. if there is still any air in the system, it will work it's way into the overflow tank...and coolant will be drawn out of the overflow tank into the engine....so the tank will need to be topped off.

rygill

Hi guys,
Thanks for the help, there was indeed air in the system, creating quite the geyser out the radiator... Anything to worry about, having all the coolant on the motor?
Thanks again.