Question about 1986 Toyota 4Runner

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Intermitant temperature 1986 SR-5, 22RE 4WD, 77K. On cold engine, temperature rise is normal and guage good. Blows hot air, temp fully adjustable. No problems with short drives, stop & start engine, temp & heater OK. On 20+ mile drives, temp steady UNTIL I shut down, even if only for a few min's. Although temp must be normal,guage at zero and heater air drops. As long as I leave the engine running, even long drives, temp remains normal, gauge OK. . ONLY when I shut it off will the thermostat apparently stay open. I question a bad thermostat as the sole problem. Noting a wired gauge, OEM# 83420, just ahead of the thermo bell housing, is this thermo electrically controlled in any manner. Schematic also shows a thermo switch, OEM# 88430. Why would shut down cause the termo to stay open and reduce temp if only a bad thermo? Occasionally dash temp gauge will jump up at ingintion start, then drop down to zero and come up with temp rise.

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  • jonesy19 Jan 22, 2009

    Thanks oddballone. Tomorrow I will do a total "run thru" from cold, to hot, etc and keep a time/distance/ log, hot/cold, heater air to tank/hose temps. Last several days, short trips and stop/ starts reveals normal operation with the temps and gauges, but need a longer 60 mph plus trip and shut down to mimic the usual problem. I'll advise and thanks again.

  • jonesy19 Jan 22, 2009

    Hi Oddballone: Thanks for your help. I don't think my comment made it thru, so I'll try again. I will try a full diagnoses with a run thru, from overnight cold, thru warm up, temps, times, etc. Ran around today, short trips, stop and restart, all was fine. Need a longer trip to mimic the usual problem and I'll get back to ya.

  • jonesy19 Jan 26, 2009

    Hi oddballone:

    OK. Last few days, did some short drives, temp. came up ok, stayed up like always, cooled down when stopped for 5-10-20 mins, and came right back to normal once on the go. So, like you said, a thermo. either works or it doesn't. If it opens it should close. Upon initial engine warm up, the tank top and upper hose stay cold even as the temp gauge begins to climb and heat is available at the blower. Ater @ 15 mins, the upper hose/tank begin to warm up and eventually get hot. Sooo, it appears the thermo is functuioning. What I initially thought was the temp sending unit located on top of the metal thermo housing, it cannot be that, as the inside temp gauge shows a heat rise while the upper hose and themo housing remain cold. NOW. Sun. I took a grandson to a local ski resort, 22 miles each way, did NOT shut down, drove back and everything was fine. 6 hrs later went back for pickup, all OK until I shut down the engine for . @ ten mins . felt the tank/hose, still very warm. Started up, the gauge dropes to C, heat started to drop lower and lower as I was returning home but never got actually outside cold. I stopped @ half way, felt the tank/hoses, warm, but not hot like normal. This is what I had experienced before. I know the thermo itself is not electrically controlled, so there must be some other devise to cause the thermo to remain fully open and circulating cold coolant constantly but only on extended trips. I shut down & restarted several times on the final trip and the gauge or temp never returned to hot normal. Next morning, all was fine again. This is quite puzzling so any ideas???

  • jonesy19 Feb 02, 2009

    Hey Thanks: As it is not a emergency condition at this stage, I'm going to wait until the temperature in my garage is a bit "warmer". I don't like messing with bolts when the metal, espcially aluminum, is cold. I looked all thru my shop manual and find nothing about the reccomended torque on the two thermo. housing bolts. Got anything in your data base? I kinda agree with you as there is almost nothing else to cause it. Pressure cap tight, system clean and tight, core fine and no coolant leaks. I'll get back to you and lemme now what you find about the torque setting. Many thanx.

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Check to make sure your thermostat works right by monitoring the warming up of your engine. With a completely cold engine, start and run the engine for a few minutes, then put your hand on the top radiator hose to monitor if and when it gets warm as the thermostat opens more and more and note the gauge reading( if it works) the top radiator hose should be unbearably hot within 5-8 minutes. If the therm. opens right it should close right aswell, staying open a little while eventhough the radiator may have cooled may be what you are experiencing causing the rapid cooling and is nothing to worry about. The Hose should not get warm very soon after starting the engine. Regarding you gauge, lets take one step at a time, verify proper op. or the therm.

Posted on Jan 20, 2009

  • Scott Feb 02, 2009

    Interesting, I think i would try to replace that thermostat, I think it opens/closes too slowly and is the cause of the problem. One little fun test you can do is to remove the thermostat and place it in a little pot of water with the new thermo. and a thermometer. heat the water slowly and watch the action of both thermostats. Both should be fully opened at its rating (use only manifacturer recommended temp. rating) and should do so at at similar rates. The same for the cooling/closing action. Enjoy

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