I was driving my truck around the other day and when i was stopped i noticed the temp gauge start to climb, so i stopped and checked it out.. it was just under the red before i shut the engine off. The heat was also blowing cold. I pop the hood, and everything is normal, no boiling coolant, and my radiator is warm at best, not even as hot as it normally is at operating temp. So i drove it to a friends house that is close by and let it sit for a day. I drive it home and it doesnt overheat. I am going to replace the thermostat tomorrow because thats the only thing i can think it would be. The only other thought i have is sometimes my tach gauge gets a little funky when its cold out (starts fluctuating when my engine is at steady rpm) so i dont know if my gauge just wasnt working.

does anyone have any thoughts? was it really overheating? could the thermostat have been stuck one day and gotten unstuck the next?

 

Very little to no coolant. Thats why you didnt hear it boiling...there wan't any to boil!! Mine kind of did the same thing for like 4 days before I replaced my heavily leaking radiator, and it sucks to not have heat at 10 degrees!....Deff check for lack of coolant, and from now on, check the coolant level every week to be safe

 

oh man am i an idiot... tons of coolant in my overflow, but none in my rad. Only leak is out of a flushing T that was installed (the hose clamps came a little loose), but its only a little bit.. so i guess ill be changing my oil to see if i need a new headgasket.

 

Aye, a leak in the coolant system can prevent the rad from pulling coolant back into the system from the resevoir tank. I learned that the hard way...seems you have too!!! I'll be surprised if you screwed up your HG. My coolant system was leaking for well over a year, ran it low a few times, and then in the last month my radiator developed a MASSIVE leak. I'm talking if I filled it then let it sit for about 6 hours, it was completely empty. I had my HG and head checked, and it was A-okay. I still have a leak somewhere though..... Good luck with whatever happens

 

the only visible leak consists of a few drops though.. would that still cause it not to take from the overflow?

 

It's possible. Are there more than one leaks/drips? You should check your rad for leaks as well. Also, I re-read your original message, and you said something about the RPMs fluctuating. Does the actualy engine RPMs fluctuate or just the tach? Mine had a fluctuation problem the 4 days before I replaced my radiator, and as far as I know, it was due to the lack of coolant and/or air in the system. So, check the coolant system, burp it so there isn't air in there, and make sure you check the coolant levels for the next few days.

 

I just fixed a coolant leak from my head gasket. It was leaking onto the motor, into the exhaust and a little into the oil. It never dropped one drop onto the floor, guess the motor would pool it or burn it off where it leaked. The smell of burning coolant was pretty obvious and got worse and worse, I would just tell my self it is an old truck and it's normal.

Can you smell coolant or notice it in the exhaust?

 

Did you burp the radiator? Could be air locked. If no one has mentioned this start the truck with the radiator cap off, and when the truck gets to temp you will see it bubble out a little. Then refill it after that. Worked for me. My truck would get super hot, and I had no heat also, so I tried the tip and it worked. Do this if you havent done it already, with any new radiator I would do it.

 

the fluctuation is only in the tach.. the engine is steady and gauge goes crazy.. it only happens for a couple seconds at a time.

i havent noticed it in the exhaust.. but im keeping a close eye.. i just had it started and running at normal operating temp and it was fine. i fixed the small leak, filled it with coolant, and burped it. The exhaust was smoking when it warmed up, which is normal for any car, but it stopped once it was warm. I tried to smell the exhaust, but the aroma of coolant is filling my garage and my nose isnt the best when its as cold as it is where im at.. so i donno if the exhaust smells like coolant yet or not..

how long did the headgasket take you?

 

I could smell the coolant burning on the hot engine, not in the exaust just to clarify.
I dident do the head gasket my self, but it was $300 and took a day.

 

Sounds like your head gasket is blown. Your story sounds very simular to mine. My Thermostat went out (stuck closed) and prevented the heater from heating up. Easy test on the thermostate it to take it out and hold a lighter under it for about 30 seconds. It should pop open. If after a 30second - 1 min nothing happens.. bad themostat.

Yes you can smell the coolant and if you have a high amount of water in your exaust (white smoke when starting before engine is warm), very good signs it is your head gasket.

When tearing apart my engine, the coolant did NOT enter into the oil pan. I did have the white film on the inside of the oil cap. Oh and I started to go through a gallon of coolant after a couple trips with the truck.

Even with all the coolant used, nothing in the oil pan. Another easy check is to look at your spark plugs if you have not changed them lately. If you find one more clean than the others, it is because it has been steam cleanned in your leaky piston.

Let me know if this helps.

 

yea. that helps. Im gonna pull my plugs tomorrow when its light outside..

since its probably a headgasket, ill be calling toyota too to see if its under the recall still or not. i heard its limited to cars with under 100,000 miles and my truck only has 97,000

 

let me just toss this out there-
if the tach starts jumping wildly, there is a problem not directly related to overheating.

however... if the coolant were to come in contact with any one of several connectors around the distributor and/or ignitor, odd things could happen.
...
... or if the timing were to run afoul for a substantial length of time, that could cause the engine to overheat...

... just a thought.

 

X2 with Abe

(yes a thermostat on the way out can stick one day and not the next. Eventually it will say stuck)

 

well i figured the fluctuation was unrelated.. im not worried about that because it only happens for seconds at a time and its only the tach, not the engine.

 

The tach, clean the coil and negative body grounds....

 

thanks jay, ill try that and see how it goes

 

So... kind of how all my spark plugs looked like this




Except for the one that looked like this?