I’ve had it with over heating!!!

So, I bought my 4Runner a few months back. It wasn’t running when I got it. Since day one it’s been over heating and I have absolutely no clue what the hell is going on. I’m really at wits end. The previous owner said he replaced the timing belt and water pump. So this is what’s happening.

I bought a champion cooling systems radiator CC1998. I bought a thermostat from the dealer. I replaced the thermostat. I’ve tried 3 of them. No matter what I do it doesn’t seem to open up. I’ve burped the system and took the top hose off to fill the cooling system up from the engine side. Jiggle valve is at 6 o’clock but no matter what the bottom hose is always cold. It’ll even get to the point that the coolant will begin to boil before it’ll open up. Ive put the front of the 4R on ramps and tried to burp the system but it’s still over heating. The thing that’s stupid is that if I take the thermostat out. It runs cold... so I know it’s flowing. I’m at a huge loss and really just want my 4R back and running. If anyone has some insight I’d really appreciate it.

 

Sure you’re not installing the thermostat upside down?

 

The thermostat only goes in one way. Every thread I’ve read about coolant systems says jiggle valve at 6 o clock. That’s what I’ve done.

 

Haven’t worked on one personably but have heard of people flipping the thermostat on other vehicles before.
Definitely sounds like something simple is stumping ya if it runs cold when you pull the thermostat but hot with it in.

 

For giggles why not rig the thermostat to stay open and reinstall it. See if it runs closer to a normal temp and then narrow down the issue

 

That’s what I’m thinking. It has to be something simple I’m overlooking.

 

Boil some water on the stove, and drop it in see if it opens.

 

Just tested all the thermostats I have. They all opened up before the water started a rolling boil.

 

Bad head gasket/cracked head. Exhaust getting into the coolant will do EXACTLY what you are describing.

 

That’s not the case

 

I’m reading around other threads and thats what seems to be the culprit in my case. It doesn’t start bubbling immediately it takes time for it to start bubbling. It won’t over heat if I’m just sitting but under any kind of load it’ll begin to over heat big time.

 

Bubbling? You see/hear bubbles in the coolant overflow tank?

 

I can feel bubbles in the top hose after it reaches running temperature. And yes it’s a rolling bubble in the overflow tank.

 

Like negusm said. Head gasket.

I had those same symptoms on my 2005 4.0 when it blew a head gasket.

 

I’m gonna start looking into it. I need to do a leak down test and see where I’ve got a leak.

 

Boiling the thermostats is the correct diagnostic procedure to determine whether or not the ‘stat is actually working. You can also put a cooking thermometer in the “soup” at the same time to verify the actual temperature that the thermostat is opening. The thermostat should open completely (spring is pretty much completely “squashed”) before the water starts boiling.

When installing a thermostat, the coiled spring on the thermostat goes toward the engine block.

The little hole with the dangling little metal valve is there to allow a very small amount of coolant to flow through the thermostat so that can accurately sense the coolant temperature, and also allow any air to get by the thermostat to help purge the system.

Borrow a cooling system pressure checker from the local parts place (you “buy” it up front, then they refund your money when you return it with the idea that you’ll buy some parts from them). Fill the system up completely and use the pressure checker to pressurize the cold system to whatever the stock pressure cap is rated at. Then sit and watch the pressure gauge. The pressure should not drop at all. If it does drop, then you’ve got a leak somewhere.

If it does leak, pump it up a few more times and look to see if any coolant is dripping out somewhere (probably not, but it’s worth a quick look).

If the head gasket is what is leaking, the coolant will most likely be seeping into one of the cylinders. To find out which cylinder, remove all the spark plugs, then briefly crank the engine over. The leaked coolant should come flying out of the plug hole of the cylinder that has the bad head gasket.

Good luck.

 

If you've already tried new thermostats, have you considered doing a compression check? That might rule out the other issues of blown head gasket and/or cracked block.

 

I'm really interested on what happened here. I have the same story, I bought a 2001 4Runner and was told the water pump was redone. It was running cold so I looked and no thermostat. I put in a new thermostat and it overheated. I tested it in a pot of water and it opened at 180. I replaced the fan clutch and radiator (mostly because they where cheap and ruled out a plugged radiator). When the thermostat is installed and under load it overheats. The heater core is good and blows hot with thermostat in. I have not done a pressure test yet but thinking that will be my next stop. When burping the system i do get bubbles at idle but when I throttle up it seems just to be moving fluid.

 

My guess is also the fan clutch. Not a very expensive fix, that is , if you haven't already ruled it out.
Other than that, a clogged radiator, or water pump.
Let us know what you find. Don't stress on it! Probably not major.

 

Oh, I did the fan clutch with the radiator. Normally it's not something bigger but I'm out of easy cheap fix's and looking that the head gasket or block is the culprit.

 

Water pump?
Heater core?

 

The heater core is fine, blows hot when the thermostat is in and no leaks. The water pump was supposedly replace before I purchased it. Looking like the guy who I bought it from might have know there was a bigger issue once he replace the water pump, maybe the reason he removed the thermostat.

 

Seems like the only other thing, could be a cracked head...hope not, but not the end of the world if so.
Sounds like you've ruled out the little things like thermostat, water pump and radiator? Here to help , if we can.

 

There are really only a few things that can cause overheating. If you check everything that has been mentioned, I'm sure you will find the culprit.

 

Time to run an exhaust gas test on your coolant.

 

Keep burping it. If that doesn’t work, focus on the head gasket. My cobra had to be burped 3-4 times before it finally stopped over heating. Start simple and work up.

compression test is a great idea