85 SR5 Toyota overheating

[Retad13]

I have '85 SR5, automatic, 22re EFI 4 cyl. I'm experiencing some overheating that I can't explain the reason. I've owned it for about 4 months
I've replaced the T-stat and the radiator cap and the radiator has been flushed. After letting it cool, I top off the radiator (it usually only takes about a quart to half gallon water, at the most) I get it up to temperature with cap off and the water is flowing across the top of the radiator just fine (so its not the water pump). I took it out for a drive and 10 miles later the temp guage shot up, not gradual, but a fairly quick jump. I let it cool again, checked the flow again (normal) and drove the 10 miles back home and it overheated again just as I got back home .
The oil is a normal color and is at normal levels.
My friends and I are stumped.
Is it possible for the water pump to stop working properly from time to time? I'm sure it works right or not, there is no "intermittent' performance for water pumps.
Thanks for any help you may offer.

[bradrhale]

what is the mix of water to antifreeze?? close to 50/50?? have you verified oil pressure??

[Retad13]

Well it WAS 50/50 at one point, but with all the refills lately its probably 80% or more of water right now. Oil pressure is normal according to guage, it could be better, I was advised at my next oil change I go to a single grade oil for this type of engine for the climate here in Arizona (especially during the summer heat).

[bradrhale]

how about the fan clutch?? is it nice and tight and dragging enough air through the radiator fins?? how do the fins look?? is the water boiling out when you say it overheats or leaking out?? 80/20 is not a good mixture and will cause overheating problems but do understand that this started doing this with the 50/50 mix, right??

[Retad13]

Fan clutch appears fine, fins look fine. The fan spins while running. I'm not a mechanic by any means, very simple stuff I can handle, but learning more out of necessity since I bought this older truck...maybe a few pointers of what to look for or how to check something (?), would be greatly appreciated at this point.
Water does not spew out at all, temp guage is 1st indicator, after I turn off and go under hood, I can certainly hear the radiator "gurgling".
Another thing I failed to mention earlier is that upon idle at stop lights or whatever, It idles rough, like its going to stall. It idles like that now even when temp guage is in normal, but not as bad as when it starts heating up.
Thanks for your help and taking time from your day to offer some expertise!!! Truly appreciated.

[bradrhale]

Originally Posted by Retad13

Water does not spew out at all, temp guage is 1st indicator, after I turn off and go under hood, I can certainly hear the radiator "gurgling".
Another thing I failed to mention earlier is that upon idle at stop lights or whatever, It idles rough, like its going to stall. It idles like that now even when temp guage is in normal, but not as bad as when it starts heating up.
Thanks for your help and taking time from your day to offer some expertise!!! Truly appreciated.

now we are getting somewhere. just takes a little time but the problem will eventually narrow itself down. no sign of leaks, im assuming from the coolant system but you are still adding water. you say that the oil color is good so i am going out on a limb to say that it doesnt look like a milk shake. bad idle as well. you might have a severe head gasket leak or cracked head/block. water is entering the combustion chamber and being burned off could be a why you are not seeing any leak. is there an unusual color or odor from the exhaust??
being that the engine has already overheated, there is a good chance that damage has been done. i wish i could give you some good news but this, until you tell me something that throws this idea out of the window, is ver suspect. however, if this is the culprit, i would not recommend you fixing it. this is a very nasty engine to break down for head gasket replacement. toy did not think too well when building this engine.

expertise?!?!? where?1?!!?!

[leolkfrm]

sounds like a head gasket, earlier yotas were known for it!

[Shadetree55]

I have had a couple of 85's do the same thing to me. Like was mentioned already one was the head gasket. Toyota's are bad about that. The other experienced almost the same symptoms you described. I changed the t stat and radiator cap. Had the Radiator flushed. And it still continued to overheat. Turns out it was the fan clutch all along. Which is a pretty easy fix. I'm not a mech by any means either so would the heater core be ruled out by symptoms?

[hotrodpc]

Sounding like a head gasket to me. Exhaust gases are probably heating up the water in the block or heads when it gets hot enough the pressure overcomes the exhaust gasses then start leaving out your exhaust and may be evaporationg before it gets out the tailpipe. One way to tell if thats the case is put an emissions sniffer in the tailpipe when its overheating. You will see some very funky readings.

[bradrhale]

Originally Posted by Shadetree55

I'm not a mech by any means either so would the heater core be ruled out by symptoms?

absolutely ruled out. the heater core has nothing to do with the cooling system contrary to the fact that it does use engine heat to create heat inside the cab. this is all that it does, though. air passes over the core creating hot air. the exiting coolant will not be enough of a drop in temperature to validate being used to cool down an engine.