Hey Everyone,

it's been awhile since i've been here or posted...

my car has started to overheat more and more. the first times i thought were understandable as i had been driving up a mountain with the AC on or through death valley with the AC on... but now my car is overheating all the time now. the latest overheating bouts have been during each direction of a 40 minute trip i made. now it's overheating on my 30 minute commutes to work. i had the timing belt, water pump, thermostat, cam shafts, and a few other small things replaced about 4 months ago.

when my car overheated i found the coolant boiling over (as it normally would if overheating) and temp guage in the red. but today... after arriving at work the coolant was boiling over again, but my temp guage was still in the middle and not in the red like all the previous times so i didn't know that my engine was getting too hot. when i went to autozone during lunch my coolant boiled over again and when i looked in both the radiator and the reservoir nothing was left in either (maybe everything completely boiled out?). I did refill both the radiator and reservoir and no leaks occured. i never saw any fluid leaking out of my engine when it was just sitting there cold or even in idling after sitting for awhile. the only time fluid would leak out seems to be when the coolant in the reservoir would start boiling from being too hot. strange thing was that i drove 30-40 minutes to get home with the sun down and had no overheating problems or boiling coolant after I had stopped for maybe 20-30 min from a short 10 minute drive that had my reservoir pouring everywhere. So it seems as though it's not consistently overheating...

i checked the fan and the fan clutch and it seems to work ok in idling. i did idle my car with the AC on for about 20 minutes at night and the fan kept going. i could move my fan with reasonable ease after the car had been running for awhile and not shut down. someone had mentioned to me that the fan should be harder to move after i had warmed up the engine, but the resistance of the fan was the same as it was when it had been sitting for awhile.

the pressure in the radiator and reservoir seems to be ok as once the car cools some of the fluid is sucked out of the reservoir and back into the radiator.

one of my friends said that it might be the heat gasket that's messed up. he had the same problem where sometimes it would overheat and other times be just fine. he also had constant coolant boiling out of his reservoir as well. could this be it?

i had initially thought maybe my fan was slowly dying since the times that i turned on my AC were the most common times that my car would start to quickly overheat. my reasoning is that the overheating seems a bit inconsistent so far and i thought perhaps the fan is cutting in and out while i'm driving. i should've checked the fan with the engine on after i found my reservoir overflowing, but i didn't think of it then. now i'm not driving with the AC going anywhere b/c i'm afriad of it blowing up and it still overheated twice. my car has about 306k miles on it and is a 97 4runner with 2 wheel drive. i'm driving in about maybe 70-80 degree heat in the morning and 90-100 degree dry heat in the evenings.

any ideas of what this maybe? any help would be greatly appreciated as i'm afraid of blowing a gasket or cracking the block. i am set to see a mechanic saturday as that's... kinda the earliest i can go right now. =(

 

have you noticed smokey bubbles in the radiator when it is idling ? this could indicate exhaust getting into the cooling system from a bad head gasket. my truck had a bad fan clutch and it still pulled air but not enough. it would get warm when idling or pulling a large hill. i don't have air on mine ,that would work the cooling system harder. what motor do you have ?

 

i didn't check for bubbles in the radiator... should i check the radiator with the car running and the cap off? it could possibly still be spinning a little. it's been progressively getting worse over the last 3 months since i had the first overheat. my car has never overheated in the 5 years that i've had it since my dad gave it to me.

i have a V6 motor. thanks!

 

check this thread. there are some things you can try in that thread to see if anything is bad such as fan clutch test and burping your radiator.

https://www.yotatech.com/forums/f2/9...estion-217954/

 

If it's OK at speed but overheating in stop-and-go/idling/slow driving, then fan clutch is major suspect. Do you hear it roar at start-up? Try using a rolled-up magazine to stop it when it is overhot, it should shred it. You can't tell anything about the clutch by spinning the fan with the engine off. Did you put in an OEM (Toyota or AISIN) water pump?

 

thanks for the replies guys.

cLin: i'm reading up on the forum and will try some of those things.

thedurk: i had a toyota water pump replacement. and for the slow driving, read below...

i tried driving into work again today and well... same thing driving in. coolant spitting everywhere, temp gauge still in the middle, drove slow (60-65 on the freeway), maybe 90 degree heat, but THIS time.... my engine started pinging a few times when i got off the freeway. was my engine already burning hot on the freeway and then getting off of the freeway limits the air coming in??? it worried me a lot.... i waited for the engine to cool, it sucked all the coolant back into the radiator (reservoir all dry now) and i tried starting my car. it's still working... for now.

friend at work thinks i have a blockage and maybe fan clutch is bad. does this extra info help any?

 

bad t stat, ive had a bad one right outta the box. sounds like your not transferring heat efficiently i would check for clogs in the radiator, thermostat, it makes mee think thermostat because the gauge stays in the middle with it boiling like its stuck closed?

 

With that many miles you may as well just redo your cooling system. New everything and flush the system.
Wont even be to expensive, and its nice to drive your yota with out having to keep a constant eye on the temp.
My 22re had a bad thermostat and radiator. New thermostat and a 3.0 radiator, it stays nice and cool, but its habit now to watch the temperature almost as much as i watch the road

 

ok guys i just went out and ran the car with the radiator cap off. i see some bubbles, but i assume that's from the t stat opening.... maybe i'm wrong.... what do you think? the radiator fluid level was bobbing up and down. when revving up to 2k rpms and turning on the AC the fan clutch seemed to work ok..... fan rpms increased with engine rpms. i'm thinking it may all be when i start driving faster that everything starts to die off. i'm still thinking maybe clogs in the radiator or clutch fan goes out and free wheels at higher rpms..... i am strapped for time so i'm trying to get the best idea i can of what the problem is before i actually try some fixes. thanks again guys!

silly question, but... will running the heater in the cabin really help disperse the heat of the engine???

 

If you are overheating on freeway at 60mph, it is NOT your fan clutch. By slow, I meant below 20mph. I discovered my fan clutch was bad appoaching the Lincoln Tunnel in stop and go traffic. I boiled over after maybe ten minutes. I let it cool for maybe 15 minutes, turned around and went home against traffic (free-flowing) and temp stayed halfway on a 95°F day. We even put the AC back on.

Yes, the heater can make a big difference. If the radiator is clogged and the heater core is not, it will make a dramatic difference. Check your thermostat first because it's cheap, but my money is on the radiator being clogged.

Do something soon, or you are going to warp your heads or blow your HG, or worse.

 

It surprises me that so many guys (especially lately since it's summer) just keep on overheating their trucks over and over, a few times a week trying to figure out what it might be. Overheating isn't like running out of gas or getting a dead battery. One good overheat can kill the top end of your engine. At the very least it will reduce the life of your heads and head gaskets. Multiple little overheats are just as bad. It can mess up your valves something fierce, warp the heads, crack them, melt sensors and wires, cause electrical shorts, etc...

Here is the best advice I can give you... Don't drive the truck while it has a tendancy to overheat. If you must drive it, keep an eye glued to the gauge and kill the motor as soon as you see the needle start rising. If you wait until it's gets in the red, you've already done some degree of damage. Is it enough to notice now? Maybe, maybe not, but your engine WILL NOT last as long as it would have without some major and expensive repairs - even if it's only overheated once. It makes selling the truck a lot more of a moral issue also because I personally would never buy a car that I knew overheated and I would definitely want to know info like that before I hand over any cash.

 

thanks guys... yea so i've been driving in 10 minute increments so now my car won't overheat now...

i took it to a shop around 4 today b/c i just couldn't wait any longer figuring it out. i take it there and...... after 5 minutes of me describing the issue and me showing them the car... pops the radiator cap and says "there's your problem". insert face palm... the radiator cap had lost it's spring and wasn't holding pressure. i hope that's the problem, but we'll see. i've been eyeing the temp gauge like a hawk.

 

Just the cap??
Please keep us updated!
unless the water is just shooting past
the caps seal but overheating?
Yes, blasting the heat drops the needle
on my runner immediately.

 

Yeah, that'll do it. The 16 or so lbs. of pressure created by the cap raises the boiling point of pure H2O by almost 50°F. So an unpressurized system will sure as sh** boil over under normal usage. The overheating with gauge in the middle was a dead giveaway, and I missed it. I would have found it if I had the car in front of me. Sorry. Modern caps just don't seem to go bad as often as they used to, largely because they are only used rarely compared to older cars without reservoirs.

 

so i drove it into work today and no problems at all. that seems to have been the problem so far on one drive. still driving it slower, but i will try to drive normally and then try it with AC.

 

yea was the problem. no more overheating or anything else.... =P thanks guys!!!