Overheating, need opinions

This is an 06, V6 345,000 one owner. The problem started yesterday. I was driving on a long Hwy, about 30 miles, when I got to the signals and had to stop, after a minute, the needle start moving up. When I took off, it cooled back down, repeat. When I got home, I was low on coolant, about half gallon. Today, I had to drive about 60 miles away. After 35 miles of mostly 65-75 mph freeway, some stop and go first, it started again. I had to pull over, let it cool a little, and added another 3/4 gallon of coolant. On the way home, doing 60-65 I made the 60 miles, including roughly 15 miles stop and go without the temp needle bouncing or surging at all.

so, I was thinking, if it were the fan clutch, water pump, or thermostat, I would think it would heat up right away, stop and go or freeway at some point. It seems the coolant is being pushed out first, then it develops air pockets which causes the up and down activity of the needle. Does that sound right. If it were overheating first causing coolant to puke out, I would think it could be one of these. But it seams like it’s being pushed out throughout the catch tank.

worst case, I’m thinking small head gasket leak that’s back pressuring the cooling system. But only when the rpm’s are up above 65 mph. If this is it, I’m screwed, no money to fix or replace, but need it to do my job. If this is determined the problem, as a Hail Mary, does anyone have any first hand experience with any of the additives that may have a chance at sealing it up since it seems small.

sorry so long, just trying to give all the info.

Thanks

 

Do you see any evidence of coolant being pushed out in the engine bay? Have you checked the oil for evidence of coolant indicating a head gasket leak? Water Pump leaking while the engine is running?

 

For a coolant leak. An additive will work on small leaks, for a time. At 350K miles things just may be worn out.

 

Run it while parked with radiator cap off...bubbles?

 

I don’t recall, but I’ll double check today.

 

yes, coolant is coming out of the catch tank. The tank is full to the top when I shut the engine down. I checked the dip stick for discolored, gravy oil. I didn’t notice a leaky water pump idling, or any where else, but I’ll look closer. I checked the fan clutch for play and spin while hot. A little play but doesn’t wobble when running, and if I flick with the finger tip, it gets about a half or less rotation. No noise coming from either one.

I was thinking later that, maybe the fan clutch gets real hot and weak from long freeway driving and gets weak and less effective, especially when slowing down for city driving, less air flow. As mentioned when I go straight to driving slower in town, no freeway first, it seem to be okay. The problem comes up after longer steady driving, then slowing down for stops etc.

 

This. You could have air in the cooling system. While the truck is running and the radiator cap is off, gently squeeze the radiator hose and look for bubbles to come up in the radiator. I’m no mechanic but I know it’s not a good thing to have air bubbles in the cooling system.

Could be time for a new radiator & thermostat?

I hope you get to the bottom of your issue and look forward to reading about what the actual problem is. Best of luck.

 

it seems like a small leak at this point, because as I said previously, I was able to drive 60 miles back home without issue. I know the additive’s aren’t a cure all, I just have to explore all least expensive options. My father in law was an engine builder and always recommended Bar’s, that was for mostly radiators. but I see K Seal has a lot of good reviews. I still want to try to narrow down as much as possible before using anything like this.

 

Easy things first, if it's only getting hot at slow speeds and not on the highway the fan clutch would be the first thing to check. Also a bad radiator cap can cause it to push out coolant and not pull it back in like it's supposed to.

If it does turn out to be a headgasket problem I wouldn't reccomend any sealers other than to maybe get you by for a bit until you can fix it properly or find a different engine or truck, they may temporarily "fix" a headgasket leak but most will also eventually plug up the rest of the cooling system like the radiator and heater core.

 

Okay, I've been working on this the last couple of weeks, here's where it lands.

First, I did need a fan clutch, I would get a half a turn hot or cold. I replaced that and the whir is back, so I know it was needed, but not the problem. When I had the shroud off, I brushed the radiator fins and back blew it out with compressed air, got a lot of junk out. Again, not the problem, but needed. Driving is still the same. Under about 65, I can cruise around for a couple days, about 100 miles, and only loose about a Qt or less. No overheating, temp stays steady at normal. If I drive extended on the Fwy in the 70 or more range, it starts to push out, I can smell it, I get about 35 miles at steady speed until it pushes enough out to create air gaps and a dancing needle.

I'm not seeing any leaks, no coolant at the tail pipe, no smoke, no gravy on the dip stick. And I don't get bubbles in the reservoir until I drive it and build up pressure, idling causes no bubbles. If I crack the radiator cap to relieve the pressure, the bubbles stop until I drive it again and get the pressure up. It seems like a small hole. I used the small bottle of K-Seal, didn't do anything. I called the company to get a little advise. He said to pull the plugs and look for the cleanest one, and that would be the one, leave the plug out, put in the Heavier K-Seal head gasket sealer, and let it idle for 30 min. He said that would lessen the pressure and should allow the coolant to enter the cylinder to help with a seal.

So, that's where I am now. I warmed up the truck, pulled the plugs, but couldn't find a definitive clean plug. There is only one that looks even remotely cleaner, but very little, they all look pretty much the same, see pic. The 3rd from the right is the one I'm talking about. I even did a compression test to see if it might point it out. I got 180 at 4 cylinders, 179 at one, and 185 at one. So, nothing conclusive there. I've been driving it all week with the heavy stuff in, and no change. So, now I'm at a loss as to find which gasket (side) and which cylinder is the culprit. I wanted to give it one more shot with the plug out like the company suggested, but not sure what to do. I thought of a leak down test, I can do it on my single cylinder dirt bike, but I'm sure the 6 will be a lot more complicated finding TDC.

Any suggestions. Again, I know this is a long shot. But I need to buy some time, I don't have the money to fix it right and need it to do my job. I'm a strong believer that, you have to at least try before calling it a day. Example, was told I need new cats 6 years ago and wont pass smog without it. I just did my 3rd smog since and passed, legally, no funny business, just perseverance.

Not sure if I did the pic right.

Thanks,

 

It may not show anything since you have a slight leak but you could get a cooling system pressure tester, pull all the plugs, presurize the cooling system, let it sit for several hours, come back and look for coolant in one or more of the cylinders.

 

Once you rule out head gasket, I'd try a new water pump, thermostat and radiator cap.
It's throwing parts at it, but not hugely expensive to try.
BUT, I'd rule out head gasket first.

 

It could be a clogged radiator. Thinking this through, the water pump is trying to push the coolant through the radiator, but since it's clogged, only half the amount is able to get through. This builds up pressure on the inlet hose and would push coolant out to your coolant reservoir. Also, during highway speed, there's enough air to pass through the radiator, thus cooling it effectively. Once you slowed down, there's not enough air passing through the radiator which is already limited by the amount of coolant going through it due to the clog.

If you have over 300,000 miles on the truck and you've never had the radiator changed, look into that as a cause for your overheating problem.

 

how old are your radiator hoses , cap , thermostat ?

 

Chemical block test before you throw anymore parts at it. The kit isn't that expensive and you can find it at napa

 

Might be irrelevant to what your problem is if there's actually a leak, but have you been able to confirm if coolant is still flowing through the engine as it should? Both radiator hoses feel hot after it's been running? Heater blowing hot air?

 

I am in same boat. Though I went and did thermostat, radiator cap, flush then just installed a new water pump. Unfortunately, it got dark out, and stopped at alternator. I may do a new radiator as it and water pump were recommended with high mileage to make sure there are no blocks and good circulation.

 

The coolant escaping from coolant reservoir is most likely a result of a leaky Head Gasket. What's going on is the coolant is entering the combustion chamber and causing an over pressure effect that... coolant has nowhere else to go but out of the overflow hole. At your mileage, I wouldn't be surprised at all.

Edit: I should add that your year Tacoma was very problematic of Head Gasket Leaks occurring at low miles.

A question..are you experiencing what could be a misfire that lasts just a few seconds at first start up? Also, start keeping tabs of how much coolant is needed to keep topped off.

A few things first to before you come to the conclusion of a leaky Head Gasket...


Check the overall condition of the radiator cap, often with our Generation Taco the little thermostat thingy will come a part as it did with mine when I over heated two summers ago. I would recommend a OEM Toyota Cap. The radiator thermostat closes at 205 degrees according tho the Work Shop Manual.

Possibility that the thermostat has stopped working and is stuck in the closed position..

You have mentioned that you have checked the radiator fins for debris/ obstructions, the same attention should be giving to the A/C Condenser as well. Obstructions in the A/C Condenser can block air flow to the radiator.

Correct any deficiencies that's found in the coolant system such as swollen hoses etc etc..


This is the way that I suggest to check for possible coolant interning into a combustion chamber(s)..

This method is how it's done at repair facilities, having the right equipment makes it easy...most of the time.
Pressurize the coolant system with a coolant system pressure tester. Some time needs to pass before looking, a few hours is what's suggested. When the proper time has elapsed, insert a bore scope into each cylinder checking for coolant.

Or, let it set overnight. Crank the motor just a few revolutions. But don't let it run, that's the key! Pull each spark plug checking for wetness and/or odor of coolant.


My symptoms for my Head Gasket Leak were similar to yours. My coolant would fill the overfill tank, but never return back into the radiator. Extended drives and especially if there was a grade/climb, temps would go up but never to the point of over heating. Eventually though, coolant would spill out. The biggest symptom and greatest indicator was a misfire at first start up when setting for a prolonged amount of time that lasted just a few seconds. My scan tool always showed the misfire happening at cylinder #4. I'm at over 300k like you , so I wasn't even mad.


Piston #4 was wet when compared to the other pistons, confirming my diagnosis..











here's most of the guts to the Radiator Cap that fell into the radiator when I overheated. Sitting at the bottom of the side plastic tank..

 

If you get your hands on a cooling system pressure tester, you could see if it holds pressure, with the plugs out check if coolant is entering the combustion chamber, like what’s been previously mentioned. Then you could also pressure test the cap. Or a block tester to rule out or confirm a head gasket issue.

I don’t think you said you tried a new cap. Maybe that’s what’s wrong. Not holding pressure, spitting coolant into the reservoir, coolant not pressurized doesn’t work as well.