Hi… Got a 1990 Toyota 4wd pickup with the 22R 4-cylinder engine. Got a very intermittent problem, where the engine overheats when going up a hill first thing in the morning. as the engine comes up to temperature (from being completely cold) the temp guage goes past the normal range and keeps on climbing. When it gets too close to the red zone on the guage I pull over and turn the engine off for a couple minutes. After restarting, everything seems OK and the engine runs at normal temp. Was thinking about replacing the thermostat (maybe it’s sticking; it probably hasn’t been replaced in 60K miles), but am wondering what sort of symptoms a water pump gives out when it is about to fail, since the engine has 190K miles on it.
Do the thermostat first. If that doesn’t fix the problem, then worry about the rest of the cooling system.
Yeah. I say lazy thermostat too.
That is, unless you’ve got way too weak a AF level and are actually pumping slush until the rad thaws out. You don’t happen to be in a subfreezing climate and haven’t serviced the cooling system in a while, have you?
Yea, I live in southern Idaho, sometimes gets down to minus 10 or 20. But I test my AF once a month during the winter (with one of those Prestone “turkey-baster-looking” things) that says the fluid is good to minus 60 or so. Haven’t changed it in about 20K miles, maintenance schedule calls for changing it every 30K.
With this many miles I would look to the timing chain as a contributing cause. Even a few degrees of timing being off can cause overheating in this engine, and a worn/stretched timing chain can cause significant variation in timing. This will be esp. noticable when hill climbing. Also check the hoses, belt, and radiator for clogging. I would set aside a Sat. for general service to include, new belt, new hoses, back flush radiator, new thermostat, check for leaks, replace coolant pump, check timing, and compression test. The pump is cheap and easy to change, and since it is simpler to do so with the radiator out, all the rest of this is just sensible preventive care. If the timing chain is bad, you can expect to spend about 300 bucks on parts and take three days to do it yourself, or about a grand to have it done. You dont say if its a carb or injected. This can make a difference in the difficulty of the work, as can the difference between ca. or fed. smog equipment.
Water pumps can fail either by beginning to leak or by erosion of the impellars. erosion adversely affects the pump’s ability to push fluid, and the flow drops rate off. If this were the cause I’d expect it to be overheating after you restart it too.
With respect to Ignoramus, the timing chains on these begin rapping loudly against the housings when the sprokets begin to wear too much and/or the chain stretchess too much. Been there, done that. The 22R is carbed, the 22RE injected, but the question is a good one. 1990 is the year they changed over.
I agree with Ignoramous about giving it a good thorough going-over, with a new T-stat (my money is on the T-stat). But at this age I’d spring the $125 for a new radiator. It has served the vehicle well.
Since you’ve gone so many miles without changing the coolant (and you’ll lose some while changing the thermostat) I would suggest that you change the thermostat, the radiator cap and the coolant. Rocketman
Check to make sure you have a radiator fan. I drove my 1990 PU bought in 200 for eight years with intermittent overheating problems (six thermostats) with five difference garages not knowing what the problem was before a car parts store clerk looked over the car with me and found it had no radiator fan. New fan and mount and it never overheated again.
I have a '91 that wanted to run hotter the faster you went…Turned out, salt spray had eaten up the copper fins that are placed between the radiator tubes. Half of them had fallen out, greatly reducing the ability of the radiator…
I’d do something now. You’r begging for a head gasket failure if the temp runs consistenly much above normal, and it does not have to be in the red in an older toyota truck.