Sudden overheat issue. (Resolved.. I think)

Not sure about the 3.4L, but sometimes the studs that hold thermostat housings on go thru into the water jacket.

If all you have on the studs going into the block is never seize, that might be the leak.

I generally use aviation sealant or RTV on any studs or bolts I suspect might go thru the water jacket. even teflon tape would be better than nothing.

Next time you have the studs out stick a wd-40 straw in there and see how deep it goes, and you'll have your answer.

 

I don't recall ever seeing a mileage reading on your truck.

I would replace the water pump and while you're at it, the timing belt. You can get a kit from EBay for around $220 that includes all Genuine Toyota parts - all four belts, tension pulley, pump, thermostat, gaskets, and seals.

I'm thinking "Airman"??? as the guy who sells the parts.

 

aircabinman, I haven't looked recently but I think that was the price for the kit a couple years back...wouldn't be surprised if it's a bit more now. But it is a legit OEM kit and still much cheaper than buying it from the dealer.

he's the only seller I would buy off eBay from, eBay is chock full of fake replica auto parts

 

I did purchase the kit and am hoping that it gets here in a timely manner as it’s my primary vehicle. His kit is like 350 now. The mileage on my truck is right about 165k. Bought it at 115k and apparently the timing belt was done shortly before I bought it. It came with a stack of paperwork and service receipts that apparently verify but I’d be lying if I said I’ve ever read through them all. Does anybody think that the water pump is genuinely my issue here, or is everybody just on the “while you’re at it” train?

 

yeah price is just shy of 350 now

 

Went back to mess with the truck again tonight. It hasn’t leaked anymore coolant since finding it Sunday night. However upon refilling the coolant again, I was able to calculate that it lost a little more than a half gallon of coolant when I found it sunday. I started the truck, cycled everything through and let it get to temperature for a bit. Shut it down and went home for dinner. Went back about an hour and a half later to see if it had leaked anything and not a drop of coolant. I don’t fuckin get this thing. I guess we will see in the morning if it has leaked anything. It was still at about 100 degrees internal temp when I went back so maybe it doesn’t leak until it’s fully cool? Honestly, I have no fuckin idea anymore.

 

Double check hose ends.....I would lose water off/on some mornings....
had a bad hose ....leak thru its plys......
looks like when thermostat was closed it caused enough extra pressure to leak for a while....
until it opened.....

 

would you, or anyone else for that matter, happen to know if you can pressure test the cooling systems without the truck being hot (opened thermostat)? I've never done it before but I guess what I'm asking is if I test it when cold (which seems to be when its leaking) will the pressure reach both sides of the thermostat and pressurize the entire system without the thermostat being open? my wife just stopped at my truck to check the bucket I placed under there last night to catch the leaking coolant. yes there was coolant in there (unlike when I went back an hour and a half after running the truck up to temp last night) but not quite enough to cover the entire bottom of a 5 gallon bucket. Last night, I wiped dry the areas around where I thought the coolant was dripping from (specifically the white plastic wire harness on the front of the oil pan just below the lip and surrounding areas) and those areas are very much wet again so its obviously coming from that area. I need to be able to pin point this.

 

Your temp gauge was fluctuating is due to no, or very little coolant contact with the temp Sensor.
Coolant was low enough that it wasn't able to circulate to the heater core.
Replace the radiator.
It is always suggested to change motor oil that has been overheated as well.
Pressure Testing;
Yes , a pressure tester will test both sides of the Thermostat.

Clean the suspected leak area with Brake cleaner & rag to make it easier for you to see the coolant leak.

 

Update: Just got my truck back from the mechanics shop last night. Pained me to take it there but I couldn't play around with it anymore as its my primary means of transportation. Long story short on Christmas day I pressure tested the radiator and after having almost nothing leak out for almost a week, i got it to stat dripping pretty good under pressure. it was dripping right down onto where the dipstick goes into the old pan (front Driver Side corner of block / oil pan. even though it was dripping pretty good, i still couldn't see where exactly it was originating from because it was just flowing down instead of actually dripping onto that flat section at the base of the dipstick. I had an appointment last Monday (12/26) to get it into the mechanic incase all else failed. I made the decision not to delay any longer and take it in first thing Monday morning. Within a few hours they called me back and had it diagnosed as a bad oil cooler. The oil cooler was a dealer only part and since my dealership is a bunch of Rockstars (not) the truck has bee sitting at the mechanics shop waiting on the part until yesterday (1/04). 1150 bucks later (another 350 if you count what I did myself) and it seems to be resolved. however I've only put about 10 miles on the truck thus far and I'm not 100% confident it was the oil cooler. Just based on where the oil cooler seems to be positioned on the block and the small area where I could see the coolant collecting don't seem to be related. my expertise obviously didn't dig me out of this hole though, so what can I say? Time will tell and fingers crossed this is the end of this issue for me.

 

My Mechanic confirmed yesterday that this was probably true and the reason why I was having such a fluctuation.

 

what I'm stuck wondering now is if the oil cooler leaking as bad as it was, was a result of the over heat or is what likely made me lose my coolant in the first causing the overheat and all these other issues. I hope its the latter because if not, then I'm likely losing coolant elsewhere for it to get that low. I mean the cooling system is a relatively closed system, no?

 

I'd bet on the latter, low coolant is going to definitely overheat things quickly. And yes re closed system.