I have a 88 4runner, 22re rebuilt about 14,000 miles ago from Sunwest Automotive with new cylinder head.

New 3 core radiator
2 stage Toyota thermostat about 8 months old
New radiator hoses
New radiator cap
New Aisin water pump
New IAC valve

The problem started about a week ago when I noticed my heat wouldn't stay warm. It would take a while to heat up and would alternate between warm/cool air and I noticed a water rushing sound from my heater core when I started it up. The idle speed would also shoot up and start surging. So I knew I had low coolant. I checked and it was about a half gallon low. Turns out the radiator has been pushing coolant into the overflow. I'm not loosing coolant, I can pour whats in the overflow into the radiator and it will fill it up. I've checked the line going to the overflow, no cracks or holes. I replaced the rad cap yesterday, but it didn't fix the problem. So that tells me theres too much pressure in the cooling system.
It's leaning towards a blown HG. However, theres no coolant in the oil and vise versa, Compression looks good; 185 on all cylinders, spark plugs look good, non of them look abnormally clean, and the engine doesn't change tone when I release pressure in the radiator. It's also not running hot (however, it is the middle of winter), I have a backup Autometer water temp gauge plugged into the water inlet and I notice the temp will fluctuate between 165-210 degrees F within a 30-40 second period.
The reason I'm thinking it could be a head gasket is because when I open the radiator there is a strong exhaust/gasoline odor and no matter how many times I burp the system, more air finds its way in. I haven't checked the torque on the head bolts, thats on the list for tomorrow. It's also had a bad pinging problem for the last year, premium fuel seems to be the only thing that can keep it at bay.... For the most part. I know thats not good on the motor.
I'd just like to get another opinion before I diagnose it. I need it for the 4 hour trip to the base over the weekend. Sadly, if it is a HG I wont be able to tackle it for 5 months, since I leave for basic training and tech school in five days. Any help would be greatly appreciated. Thanks in advance!

 

If its bad enough try this trick. Leave the radiator cap off, make sure coolant full to the top and crank the motor over. If it shoots out of the radiator then its the head gasket. Another way is to pressurize each cylinder with shop air (leave radiator cap off) and see if you start getting bubbles coming out of the radiator.

 

Yeah, I had this happen to our Civic. No water in oil but one evening, it just overheated. When I checked the radiator, I found that the radiator neck was blown off the radiator. Must have been pressure from one or more of the cylinders.

I had tried this on my 1986 4Runner, and the coolant splashes some amount. Engine was rebuilt 2 years ago and it's not losing or overflowing much coolant, so I guess this is just from the shaking of the radiator, or from the water pump running perhaps?
[YOUTUBE] [/YOUTUBE]

 

Hard to tell from the video but that could be normal from vibration or impeller movement. I like to have the cap off and then start it, that usually gives you the best chance of seeing it with that sudden burst of compression. If its bad you usually get a gyser.

 

I started it with the cap off and I didn't get a geyser, but coolant did spill out and there were a lot of bubbles. So it looks like a headgasket.... Awesome, glad I spent 2k on that engine.

 

Since you've just recently overhauled your entire cooling system, my thought is to check for an air bubble trapped in the system. That would explain your temperature fluctuations and localized boiling which is causing your radiator cap to release pressure.

Search on here for "burping" the cooling system. From what I've read the 22re is particularly difficult to get all the air out and generally involves raising the front end of the vehicle pretty high and running the engine with the radiator cap off for a while.

Edit: Sorry, I just re-read your post and noticed you have burped it multiple times. Still might want to try again with the front end raised as high as you can get it. Worth a try before you pull the head.

 

Edit: Deleted.

 

Yes 854x4, I started cold with cap off. O.P. says HIS
has a lot of bubbles.

Concur. Good excuse to find a good steep hill

 

I woundnt condem the engine just yet. Like everyone says try burping the cooling system again. If you have access to a air compressor you can pressurize each cylinder and watching the radiator for bubbles to see which cylinder is at fault. Pretty much a leak down test.

 

I burped the system again, it was full of air. Drove it for a little while but the problem just continued. Not going to have a chance to do a leakdown since I leave tomorrow, it'll have to wait until summer. Not all bad though, just gives me an excuse to put an LCE performance head on, and maybe a camshaft.

 

Let's talk again when you get back. Best wishes from your fellow veteran.

 

Another quick check you could do is to see if your plugs all look the same or if one is really clean. The blown head gaskets I have experienced have been where the coolant basically just goes out the tail pipe from entering the combustion chamber then to the exhaust valve. When I tear a motor down, I have always had one shiny piston.

Something I have noticed on a few engines is when I have the valve cover off, I will set my torque wrench to about 60 pounds and do a quick check on the head bolts. 60 is below the correct torque but is tight enough to see if any are loose and you would be surprised at how many times I have found loose head bolts.

I was working a neighbors truck and one head bolt was literally finger loose. Surprised it had not blown the head gasket and so far is still holding up. Luckily he does not drive it that much so must have been what prevented it from blowing.

The third 22re truck I bought, about 3 months after having it, it blew a head gasket and it was from a loose head bolt. Not sure what causes them to back off.