Topic: 87 4runner running hot *UPDATED*

[vegastoy]

I have been chasing this gremlin for months now and I'm at the end of my rope.

It's an 87 4runner 22re 5speed. It can idle and drive in city traffic all day without issues it will run at 195-200 (has a new 195 tstat). As soon as I get on the freeway it starts to warm up. Doesn't matter if its flat, uphill, downhill. I have an aftermarket autometer gauge that is accurate. It will run at anywhere from 210-230 on the freeway. Air temp doesnt matter either it was 75 yesterday and it got up to 210 on the freeway.

I have installed a new OEM fan clutch, new heavy duty 3 core radiator, new radiator hoses and cap, new tstat. The water pump is not that old and when the radiator cap is off I can rev the motor up and see coolant flowing through the radiator so I know its working also. Theres no oil in coolant or coolant in the oil and it runs fine so I dont think the head gaskets the issue either.

I adjusted the valves yesterday and they were all very tight (fairly new motor). I adjusted them to 7 & 11 cold. Seems to run and idle better/smoother. I also installed a new OEM TPS sensor a couple months ago cause I could not get the old one into proper adjustment. I got the new one installed and properly adjusted but when I jump out the T & E1 terminals the check engine light flashes but the timing/engine speed does not change. I set the timing to 13 without the jumper in.

Any ideas what would cause the timing issue?

Any suggestions for the running hot issue?

Thanks, John

[4runner]

Do you have a shroud on your radiator? If not then that could make it run hot.

[H8PVMNT]

Could your guage be lying to you? I had a fan clutch go bad once but I would think at freeway speed you would have enough air flow anyway. Other than that maybe you are running lean but I would think you would be getting a code from that...

Play with your heater and see if there is any variation. I had an '87 22re once that would get a little hot at highway speed and when I turned the heater to full hot and back to full cool again after a few seconds it would snap out of it and cool down.  Never did figure that one out.

[vegastoy [OP]]

Do you have a shroud on your radiator? If not then that could make it run hot.

I have the OEM fan shroud on I am missing the little half moon shaped piece that goes on the bottom half though...

[vegastoy [OP]]

Could your guage be lying to you? I had a fan clutch go bad once but I would think at freeway speed you would have enough air flow anyway. Other than that maybe you are running lean but I would think you would be getting a code from that...

Play with your heater and see if there is any variation. I had an '87 22re once that would get a little hot at highway speed and when I turned the heater to full hot and back to full cool again after a few seconds it would snap out of it and cool down.  Never did figure that one out.

I'm on my second after market gauge (running a good autometer currently) and they were both reading the same so it's definately not the gauge. I would try playing with the heater but the damn cable that goes to the heater valve is broken...

[vegastoy [OP]]

I think I'm going to pull the front bumper off this weekend and test run it. I'm just wondering if the winch plate might be blocking to much air flow to the radiator?

I know its more than likely not the issue but I'm running out of ideas...

[2manytoys]

It's probably your lights. My truck started having highway speed over heating after I put my winch on. ONLY above 65 mph. Must be disrupting airflow at that point.

If it doesn't over heat at low speeds, I think your losing airflow across your rad at high speed.

Only other thing I can think of is your lower radiator hose sucking shut at high rpm's. Never seen this on a Toyota but, I have seen it on other equipment. Usually on hoses that are supposed to have a spring inside to keep them from collapsing but, are missing the spring. Also seen it on oil soaked hoses that get real soft. You said new hoses though.

Did the problem start after you put the bumper and lights on?

[vegastoy [OP]]

It's probably your lights. My truck started having highway speed over heating after I put my winch on. ONLY above 65 mph. Must be disrupting airflow at that point.

If it doesn't over heat at low speeds, I think your losing airflow across your rad at high speed.

Only other thing I can think of is your lower radiator hose sucking shut at high rpm's. Never seen this on a Toyota but, I have seen it on other equipment. Usually on hoses that are supposed to have a spring inside to keep them from collapsing but, are missing the spring. Also seen it on oil soaked hoses that get real soft. You said new hoses though.

Did the problem start after you put the bumper and lights on?

Honestly I dont really know. I have only owned it for about a year. I bought it from a guy in cali and drove it home 4 hours to vegas and it ran at 180 the whole way home. Then it spent the next several months of it's life in the garage and driveway getting prepped for paint and put back together. When I bought it and drove it home it had an arb bumper with the same lights on it. The lights sat a lot closer to the grill with the arb and now they stick way out there and there a lot closer together. You might be on to something I will take the bumper off this weekend and test run it.

The day I got it home.


Almost ready for paint.


Fresh out of the booth.

[2manytoys]

I'm sure you've seen wind tunnel tests. Subtle changes at the right speed can really screw air flow up. Those lights may be OK at low speed. The air may flow around it and into the rad.

High speed may just completely deflect air away. Just a guess since you seemed to have covered everything else. Let us know how it works out.

[Rocksurfer]

When I first put these lights on my truck I would run a little hotter than before I had them. Originally they were all at the same height, I added a spacer on the center lights which moved them up and out above the outside lights this gave more airflow and the temp went back down to normal.

[H8PVMNT]

Well your truck looks great anyways!

[Dirt Mover]

I'd try swapping in another thermostat. I had a new one that would stick open while coming down from the mountains and it caused my truck to run too cold.

[vegastoy [OP]]

Just got done with a test drive. I pulled the lights only and left the bumper on. Air temp is 65-70 and it still got up to 205. It might be slightly better than last weekend in the same air temp it got up to 210. Got off the freeway and cooled down to 195.  I'm going to pull the bumper off and try it again later today or tomorrow.

If that doesn't work I'll try another new t-stat. What temp does everyone reccomed? Should I go with another 195 or try a 180?

[sparkys83yota]

I always just get a toyota t stat. I am not sure what temp they are.

[vegastoy [OP]]

I test drove it yesterday with the bumper off and was rewarded with the same results. About 205 on the freeway and as soon as I got off it dropped down to 190-195.

I'm gonna order an oem tstat and oem radiator cap. Both are already new but aftermarket.

Does anyone have any idea why I can't set the base timing? Is there something else besides an improperly adjusted tps or a check engine light? Bad coolant temp sensor maybe...?

[2manytoys]

vegastoy, what did you find? Did you get it fixed?

[old school toy]

 check for blown head gasket.......block tester?.....

[helipilot77]

only thing I can think of if it isn't the T-stat or a head gasket is that you have a bunch of sludge built up in the coolant passages in either your block or the head ( which is where most heat is created). If you still can't find the cause, throw an aluminum replacement radiator on it and be done.

[vegastoy [OP]]

vegastoy, what did you find? Did you get it fixed?

I'm still working on it. I talked to a tech guy at lce and he seems to think its got something to do with not being able to set base timing. He said possibly the knock sensor or computer.

I unplugged the knock sensor while it was ideling and I didn't get a cel so I think he might have me pointed in the rite direction.

Currently out of town till dec 31 so I won't have time to tinker with it for a while but if/when I figure it out I will definately post my findings.

[vegastoy [OP]]

check for blown head gasket.......block tester?.....

I did a compression test a few days ago and cylinders 1,2,4 were all 165. #3 was 160. So that seems ok from what I have heard.

only thing I can think of if it isn't the T-stat or a head gasket is that you have a bunch of sludge built up in the coolant passages in either your block or the head ( which is where most heat is created). If you still can't find the cause, throw an aluminum replacement radiator on it and be done.

I just installed a brand new 3row copper/brass v6 radiator with new coolant about a couple months ago. I replaced a perfectly good thick single row all aluminum radiator (one of the toyota 4x4 vendors sells it). I still have not installed a oem Toyota t-stat to replace the one I installed with the radiator. It's on my list of things to do when I get back in town.

[vegastoy [OP]]

*UPDATE*

I have finally found some time to work on the 4runner again. I installed a oem tstat and reset my tps, didn't help at all.  I ohm tested the knock sensor wire from the plug to the computer and its good. I have discovered that not only can I not set base timing but the timing does not advance when the engine is reved up (no jumper). My 85 rec does rev up like its supposed to. I think this would possibly explain why its running hot on the freeway if the timing wont advance. I did some work on google and found a guy that had the same problem and replaced the igniter and fixed it. I swapped the igniter from my 85 to the 4runner and still no difference. I ohm tested the wires from the igniter back to the computer and they were all good.

Any ideas on what would cause the timing to not advance? I'm think possibly knock sensor or computer. 

I'm ready to burn this sob to the ground!

[vegastoy [OP]]

Also does anyone know where I can download an fsm online? Seems like all the old links to fsms have been taken down...

[tyes]

I had the same issue for a long time and was concern driving it on the free way or long distance. So, this is what I did:

1. Got me a ford tauras fan at pick a part for $25 bucks + entry fee..
2. drill 2 little wholes in my T-stat.
3. did coolant pressure test for leaks, which I've found one the size of needle hole or smaller...

since then issue solved!!! Drove it on a 9 hrs trip one day and it was cooled all the way. I didnt worry about air coming in as this taurus fan sucked huge amount of air just on LO setting..

[vegastoy [OP]]

I had the same issue for a long time and was concern driving it on the free way or long distance. So, this is what I did:

1. Got me a ford tauras fan at pick a part for $25 bucks + entry fee..
2. drill 2 little wholes in my T-stat.
3. did coolant pressure test for leaks, which I've found one the size of needle hole or smaller...

since then issue solved!!! Drove it on a 9 hrs trip one day and it was cooled all the way. I didnt worry about air coming in as this taurus fan sucked huge amount of air just on LO setting..

Did you have the same timing issues I'm dealing with?

I would really like to fix my timing issue which I believe will also fix my temperature issue.

[2manytoys]

vegastoy, Thanks for updating your post. I found out the FSM links were taken down also. Ended up buying FSM's from ebay and amazon used.

Are you sure the 85 ignitor is the same? If other year parts work maybe borrow a buddies knock sensor, ECM, etc. I know some years are interchangable. My 88 is not unfortunately.

[Slowdave777]

pull the tstat and run it without. simple test, if it stays cool look at water pump, and unfortunately head gasket.

[tyes]

Did you have the same timing issues I'm dealing with?

I would really like to fix my timing issue which I believe will also fix my temperature issue.

Same issue buddy. I would do the leak test first through the radiator. that should tell you if there is any leaks.. Also check the heater core control valve. small little holes size of hair can cause over heating and that leak test will find it.. your eyes wont... 

[Cali-yota]

bringing this old thread back to life.  Vegastoy, did you ever figure out issue?  Having same thing.  Just had top end redone and doing same thing.  Only at highway speed does it heat up.  I'm thinking maybe thermostat but that seemed fine on yours and mine is non-oem but new.  Also is is possible for the water pump to be good for low rpm and not high?  Cheers all.

[Win243]

My 4Runner used to have the opposite problem. It would stay plenty cool on the freeway where there was airflow, even with spotlights attached. But it would get hot when crawling/idling/in traffic.  It turned out to be the fan clutch.  I can't imagine why yours would get hot at high speed only.  I can only think that it might be a head gasket or coolant obstruction as others have said.

[kneedownnate]

The ones I've had get hot on the freeway had a very plugged radiator.  Disconnect the hoses and run water through it at high pressure, then feel along the radiator till you hit a point where it is not cool from the water flow.  Mine was plugged by about 1/3