I have 1999 4runner 4x4 with a 3.4L engine. 75,000 miles

It seems to run great, but about 2 weeks ago while my wife was driving it up to her parents house in the mountains, it overheated. From what I understood it was very near the red, or possibly in the red on the gauge.

Some coolant came out the overflow container.

I drained all the coolant out, and put fresh coolant in at the proper 50/50 mix.

after that I made the trip up the same road and it did the same thing, but I did not let it get as hot as she did, I was watching the needle climb and pulled over before it got too hot.

So I replaced the water pump, T-belt, thermostat, and radiator cap. (I like to get my hands dirty!)

and again it did the same overheating. I tested the clutch fan according to the hayes manual, and it tests fine.

I am guessing head gasket issues now. it NEVER overheats around town, stop and go traffic, drive thru's, and has never done this before.


I want to add that we bought the vehicle about 13,000 miles ago, and it was a rebuilt rig thanks to a frontal crash. However all parts are new since then as far as clutch fan, radiator, condensor etc. AND in all those miles, not a single issue, and we made tons of trips up to my wifes parents place in the mountains, and never an issue.

the city elevation is 1900 ft and her parents place is about 4,000 feet.
at first I was thinking cheap fuel was to blame, but thats not it, or other people would be having the same problem.

I do not have a problem with replacing the H/G myself, but I would like an opinion or 2 before tearing into it again!



thanks

 

don't replace hg until you find the exact cause of the overheating

test the coolant for exhaust gasses, test the oil for coolant,

taste the drool out the exhaust pipe for sweetness

 

It sounds like you like to work on the rig yourself so I hate to tell you to have someone check if for a head gasket issue. If you have a hg issue you should be able to see oil in you coolant. There is a chemical you can buy that you put in your oil and if it gets in your coolant it changes color. Good to get in this situation.

How did your coolant look when you took it out the first time? Also has it been in any mud lately. Another good check is to turn it on, and check to make sure all of the hoses have equal pressure. This will check for a blockage. Also when you put the new coolant in was the rear of the vehicle higher than the front for any reason. This easily can cause air pockets. 75k is pretty low mileage for a head gasket, however it might have one now after the overheating. Good luck

 

thanks for the replies, as far as the oil, nothing noticeable, so perhaps I should get the additive that changes color if there is coolant present, if there is any it would too be much at all.

as far as the coolant, it did not look bad, but the coolant tester I have showed that it was not as strong as it should be, so I didn't mind replacing the coolant.

as far as the water pump, and t-stat , and t-belt, don't mind doing that either due to mileage, it was pretty inexpensive thanks to me doing my own labor!

I also do not have a problem having a shop diagnose it for me, but that costs money and I hate paying shops! I can normally diagnose, and repair any issues that come up, but every once in awhile I get a curve ball thrown at me!


I need to get the attachment for my compression tester so I can check that out next.

if anyone has any extra info in the meantime I would appreciate any advice!

thanks

I am also in the middle of moving, so I may not get a chance to reply on this for a few days.

 

Mr. Gasket Block Check is what that stuff is called. It starts out Blue and goes into the coolant, if any exhaust gasses get to it it turns yellow. Check it out, but it had a head gasket issue you would likely notice a power difference and possibly a blown radiator.

Did you get a chance to check to see if all of the hoses had equal pressure? I would guess that your radiator is clogged or you have an air pocket. Check the hoses while running for the air pocket and take the rad cap off when fairly cool, then run the car with the front significantly higher than rear to see if there are air pockets.

I seriously doubt that your thermostat is bad since this happen with both of them. However my buddy brought a brand new one one time and it didn't open. If you place it in boiling water you can watch it to see if it opens.

 

You probably have an air pocket, mine did the same thing awhile ago after I did a radiator flush and I guess I forgot to burp it of air. I just refilled with new fluid and some wetter water surfactant and I've had no problems since.

 

I did not get a chance to check anything out yet, the wife uses it to get to work, and have been packing and moving things, but I should get a chance this weekend to do some checking.

I want to add that this happened BEFORE I did any work, and 13,000 miles after the radiator was replaced with a new one, it just all of a sudden started to overheat, but ONLY when driving in the mountains, and even then, it takes 3/4 the way up the hills to get to the overheating.

I am not going to rule out a clogged radiator completely, but it only has 13k miles on it.

and also I have a funnel that attaches to the radiator so while its running, air is immediately replaced by coolant, I have done many coolant flushes, and its a very handy thing to have, its a great way to avoid a mess!

I also did add some water wetter to the mix, and it didn't change anything.


It was 105 here yesterday, and although we live in town, we live up a pretty steep hill thats about a mile long, and not a single problem with overheating. it doesn't seem to like the longer trip up the mountain (about 15 miles), but otherwise does fine.

I think I will try the 2 additives to check the oil and coolant, at least I could rule out a HG.

and it has plenty of power. It hasn't seen any off road adventures in about 5,000 miles, and even then it wasn't any crazy mud pits or anything (its the wifes rig, and she gets mad if I take it off road!

 

Just curious, but was your a/c on while climbing these hills? These rigs have been known to heat up when climbing hills, especially if the ac is on, I know my rigs r 3.0's not 3.4, but they do the same thing when I go into the mountains on a 105* day, with the a/c on. Otherwise... are you loosing any coolant? I would suspect coolant loss with a h/g failure. Also, keep in mind, that you will not always get coolant in your oil, or vice versa when these h/g's fail, my 93 has a failing h/g, and no coolant in oil, or vice versa, it either drips down the block or gets burned up and pushed out the exhaust...any white smoke? Also...just curious, what type of coolant are you running? Dexcool? If this vehicle had dexcool in it at one time, and was not completely flushed, then replaced with traditional coolant, they have been known to coagulate and clog things up.....good luck!!

 

Was the T-Stat you replaced the factory temp? The guy at AdvanceAuto told me to replace mine with a 190 or 193 while stock was 180-183. My truck overheated the first week. Needless to say, I went back to the 180.

Just a thought.

 

I had an over heating issue on my samurai one time. And i did everthing from change the t-stat (and trying different temps t stats, but always stick with what is recomended) I flushed the radiator and replaced the coolant, changed the water pump, got rid of the clutch fan and put an electic fan on. checked for a HG issues. Checked for air pockets. Man i did everything and it came down to replacing the radiator. Turns out the radiator wasnt flowing enough coolant cause it was partialy clogged with mineral deposits and gunk.

Hope ya get it fixed soon before you overheat it 2 much!

 

Well, not much to report back, no leaking H/G . I drove it to the coast (about a 2 and a half hour drive) which included inclines and the needle never budged. the whole trip not a single movement of the temp gauge past the normal middle of the gauge area.

But, when I got back to town, and drove up the steep hill to my house, it made it up to about 3/4 on the gauge which is still "OK" but it had NEVER done that before, and I know if I took it back up the mountain road it would still overheat.

and if I drive at highway speeds, and then come back home, even after just a short 15 minute highway cruise, and head up my steep road to the house, it does the same thing, about 3/4 up the gauge. The air temperature seems to have NO effect on this because I have done the same thing in the morning when its in the upper 60's- low 70's and it does the identical thing. so it has to be related to something in the cooling system.


anyone else have any ideas?

Not sure if I mentioned this before, but I even have an auxillary tranny cooler ( just to keep the temps down on these hills, but I never had any issues without it installed either, but it can't hurt!



it just seems a little weird to be so specific to a steep incline, and have no effect any other time while driving it.

 

Hmm. Sounds like there's something on an incline that is keeping your coolarnt from flowing but off the top of my head I can't think of what it would be.

Did you replace the T-stat? Maybe it closes up when you're going up a grade. I don't know.

Maybe some air in the system that only becomes apparent when going up grade? Try flushing the coolant maybe or turning the heater on for a bit.

These are guesses and not facts.

 

how are you reading temp ? on the dash or from the ecu ?

each one has it's own sensor.


verify they both report hot or cold. need a scanner to read temp from OBD port

 

t stat replaced, coolant flushed 3 times so far, tried the heater ON to circulate coolant through the heater core. Nothing I have done has made any difference.


and as far as how I am reading the temp, the gauge on the dash, BUT it WILL overheat on an extreme incline like heading up the mountain road for a few miles. and when it gets near the red, it will start kicking coolant into the overflow tank.

it has not been past the 3/4 mark lately, but I have not been up the mountain roads either.

and ONLY on steep inclines.

 

I wonder if it's the extra load on the engine pulling the truck up the steep hill, or simply the angle the truck is in that interferes with the cooling system operation. If you sat your already-warmed-up truck in neutral on a steep incline and revved the engine for a while, will it overheat?

 

It will not overheat while idling on a steep incline. I did take the truck in to a shop. They said nothing is wrong aside from some inconsistent temperature readings across the radiator.

SO I ordered a new radiator, and will install it next week when it gets to my door. and HOPEFULLY this takes care of it.

I mean the radiator only has 14k on it as is , but I guess anything can happen.

 

Was it an aftermarket rad? I've heard the 5VZFE doesn't like anything but the factory rad. How's the fan shroud?

 

ahh...good point mt_goat... I forgot to mention that my fan shroud is no more, and that is likely the cause for my heating up on big hills when hot out.

 

Same thing happend to me this weekend down at the beach, took the
4runner out on the beach in the sand and it was doing awesome, then it started overheating. I was running between 2500 and 3000rpms. The needle was in the red, there was pinging, knocking and loss of power. I had to stop a few times to get the temp back down but it wasnt coming down fast enough or enough. The overflow container was full of coolent bubbling/boiling because it was soo hot.

I finally made it back to the road and after about 2 miles the temp was back under halfway on the gauge again. After engine cooled down, overflow container was back to its regular level and the radiator was full again.

I had timing belt, water pump, coolent flush and t-stat replaced in 05 at 90k miles. I have 124k now.....Do you guys think the t-stat needs to be replaced again? I will be doing a flush this week and changing my hoses.

 

the fan shroud is like new.

the radiator was most likely NOT factory, due to the frontal crash, and it is cheaper to get after market rads.

I ordered an aftermarket rad, a spectra one off rock auto.

hopefully that does the trick.

If it doesn't fix it, then the shop needs to get slapped around for not finding the real cause.

After I got it back from the shop, and still to this day (a few days later) it smells like antifreeze around the car when its been running. That smell did not appear before I brought it to the shop.