CMBTMEDIC

Okay so I have been beating my head with my 4Runner

I have a 1997 4runner SR5 4WD with the 3.4L with 160xxx miles

I tore the engine apart because I had a "cracked head gasket" just to find the people before me had changed the head gasket and never tightened down the head bolts. SO I changed both head gaskets, took the heads in and had them milled and inspected. Everything is fine. Got everything back together and got it running.

Now I have a major overheating issue. I can't drive more than 3 miles without the water boiling. I have a NEW Yota water pump and thermostat that I just installed..... I hate the timing belt on this damn car. All the belts have less than 5K miles on them. I took the radiator out and took it to a radiator shop and they flow tested it and said it is working perfect. I have tested the thermostat buy placing it in water on the stove and it opens at exactly 180 degrees.

Now when the engine overheats the upper intake is burning up and the lower is Ice cold. Along with the radiator the upper 1/3 i will burn my hand on and the lower 2/3 is ice cold.

I have also replaced the ECT sensor that is under the fuel rail.

I also make sure to unhook the heater hose when I fill the top of the engine as to eliminate any possible air bubbles.

Anything that y'all can shed on this would be great. My last option is to take it to a shop and give over the rights to my first born to find the problem. :read it:

68W Combat Medic
C-Co 1/186 IN

kball

No expert on this but I believe the head gaskets can be installed on the wrong side and the bolt holes will line up but it will block some of the other ports like the water ports. Are you sure you have them installed on the correct sides? I think they are marked L and R and there's a tab that hangs out past the block so you can see the letters even after install. Again, no real experience with this, just something I think I've read on one of these forums.

rworegon

Toyota uses left and right are as if you are sitting in the driver seat.
Are you filling the block through the upper radiator hose before start up?

Basnbuks

Check your radiator cap seal , could be bad. Also thermostat maybe sticking

dbole

Here is one thing to look for. When you replaced your heads, did you also replace the valve cover gaskets?? This happened to me after I put in my engine into my 97 body. I had to redo all the wiring and I pulled the valve cover off. After replacing everything, I had an overheating motor and the radiator fluid was leaking. I replaced the valve cover gaskets, and have had no problems since.. Try that,, I bet it solves your problem

CMBTMEDIC

Thank you all for your replies.

As per the filling of the block: I pull the rear heater hose off and fill though the upper hose into the block. Pulling the rear heater hose allows the air to escape.

As per the valve gaskets: I have replaced all the upper gaskets. All valve cover, all spark plug, all intake.

As per the head gaskets on in correctly: I am really hoping not. I haven't been able to check yet as it is at my in-laws and am unable to travel there till this weekend.

tantacoma

Did you install brand new head bolts? On my 2.7 motor, they are one-use only (torque-to-yield) type. I assume the 3.4 is the same.

CMBTMEDIC

Thank you all for your replies.

As per the filling of the block: I pull the rear heater hose off and fill though the upper hose into the block. Pulling the rear heater hose allows the air to escape.

As per the valve gaskets: I have replaced all the upper gaskets. All valve cover, all spark plug, all intake.

As per the head gaskets on in correctly: I am really hoping not. I haven't been able to check yet as it is at my in-laws and am unable to travel there till this weekend.

As per the radiator cap: brand new cap but could be bad.

CMBTMEDIC

Yep brand new head bolts all torqued to specs

BMcEL

x2 on reversed head gaskets.

CMBTMEDIC

Okay so update. The head gaskets are on properly, I put a brand new radiator in. Now I am still having over heating issues. It seems the thermostat isn't opening until I have shut the engine off... It does open and you can hear the water rush into the engine after the engine is no longer running... So any thoughts? Also picking up a radiator cap from Yota maybe the after market cap is no good.

YotaWoRx

How much coolant did it take after the rebuild

BMcEL

Is the thermostat oem? If it has a jiggle valve, make sure it's at 6 o'clock. If it doesn't, drill a 1/16" hole in it and put it at 12.

Some people claim that elevating the front end helps when burping it.

blandis

Run it without the thermostat and see if it overheats still.

WSM may say 12 for the valve. Many on here say 6 regardless of what the manual says.
I put mine at 6.

rworegon

The FSM for the 3.4L 5vz-fe says jiggle valve at 6. We have several threads around on the topic.

tantacoma

I'm thinking there is a real stubborn air pocket in the cooling system.

rworegon

This on backwards HG placement or this on t-stat jiggle valve placement.

OP, you write in the first post "I can't drive more than 3 miles without the water boiling." What do you mean by water boiling?

BMcEL

Didn't realize it was a 3.4. In that case, 6 o'clock is correct.

YotaChick

Did you ever find the solution? I am having the same problem... new gaskets, new thermostat, new water pump, burped the coolant system when we filled it... cannot go 3 miles without overheating.

CMBTMEDIC

Okay so finally got her not to overheat! The dealership told me to put the jiggle valve at 2 o'clock position. I changed it to 6. Also I went out and bought Prestone radiator flush and cleaner. I put the cleaner in and ran it 30 a night for the last week. Then I drove it around for about 20 min with the flush still in it. Got it back without the temp going over 208. Drained the flush and filled it with coolant. The filling process took me well over 2 hours, I had it on a fairly decent incline and filled the top end and the radiator. Then I let it run and burp, I had both front and rear heater cores running full blast. She runs just as good as before I started this project at thanksgiving!!