Topic: 94 4runner over heating

[bc81bc]

I just started driving this 94 4runner with a 22re this past thursday.I have had it for a while but I have just moved is around a few times.I drove it all day thursday put about 100 miles on it or so but everytime I stopped I noticed coolant coming out the overflow and I just assumed it was overful.I was driving home that night and it overheatsed on me but I just assumed it was the rad because I knew it was in rough shape.
The next day I changed the rad but it did the same thing it would build up pressure and push the coolant out the overflow.
Then I changed the waterpump and the thermostat and still the same thing.So after all that I let it run for a while it it would rev up and down then it would idle normal for a while thern it would do it again.I noticed that the coolant lines on the throttle body wern't getting warm so I decided to change the throttle body and that didn't work either.
I just dove home from a buddys house and the heat would come and go and when i stopped at lights it would rev up and down.I have never seen this problem before so I am lost.

[Willy Mammoth]

By now you may have a blown head gasket or cracked head.

Before you go there, you need to check a few things.

Look for milky oil or water water under your oil fill cap. Also is there any oil in the radiator?

Do you feel any hot air blowing from the fan or does the top hose feel cool when it should be hot. You may have a bad thermostat.

I would remove the thermostat and run it without to see if there is any change. If it runs cool and don't burp coolant, you will need to replace it with a new one. The EFI will need the proper temp range to work properly.

If it is building pressure when it is cold you have a blown head gasket.

Check these and let us know what you find.

[bc81bc [OP]]

I have already checked the oil for coolant and the coolant for oil and there is nothing there.I have also pulled the plugs and they all look normal.So if it is a blown head gasket there is no coolant going anywhere except out the overflow.Thats why I find it hard to belive that it is the head gasket.
I have put a new thermostat in it but I am going to take it out and run it like that to see if the coolant will flow and not build pressure.
It also doesn't build pressure when it is cold just after it warms up when the thermostat opens.
Does anyone know if the coolant sensor on the front of the intake cause it to do that or not?

[79coyotefrg]

when  the headgasket  blows  it depends  on where it blows  as to how it acts.    i have seen them blow  and makes  the milkshake,  i have seen them blow  and just  push oil into the radiator

i have also  seen them blow between the firering  and a water jacket  and just build pressure  in the cooling system,  pushing the coolant into the overflow,

[bc81bc [OP]]

I relize that the HG is a good possibilty I just wish I could know before I took it all apart.I don't want to waste an afternoon working on the head gasket if I am overlooking something.

[79coyotefrg]

there is a kit  you can get  that  is kinda like a coolant  test,  its  a test tube basically  that has this chemical in it  that  turns colors  if there exhaust gases  in the coolant

just suck some coolant in it  and if it turns colors  your screwed,  if not  look for something else

[bc81bc [OP]]

I decided to take the second thermostat that I tried right out and it is working now its just running really cool but at least it isn't building pressure.
I'm going to go buy a new thermostat tomorrow and put it in and hopefully the problem won't come back.

[bc81bc [OP]]

I went and picked up a second thermostat tonight and put it in the truck and it was been running good.
I must have been unlucky with that first thermostat that I bought.
Thanks for your help.

[bc81bc [OP]]

After 2 brand new thermostats I'm still haveing a problem.If i start the truck in the morning and let it run for a while right before the thermostat opens it revs up and down intill it opens up all the way then after that it runs fine.
When I am jusdt idleing through town driving the truck easy whenh I come up to a stop sign it will rev up and down every once in a while.When I drive the truck hard like rev it up to 5000 before shifting it won't do it.
I checked out the compression and it is all between 160 and 165 all the plugs have normal wear with nothing out of the ordinary.
I know that when a truck revs up and down like that it means the coolant is low but it is right up.
This problem is really driving me crazy if anyone can help out.

[bc81bc [OP]]

I drove my truck to a buddys huse tonight and when I got there I just let the truck sit there and idle.After about 10 or 15 mins tyhe truck started to idle up to a bout 2000 for a min or so then it would idle back down.It keep doing this over and over.I felt the top rad hose it was warm but the bottom was cold.The top of the rad was hot on the left hand side of the cap  but not the right side.
After standing the looking stupid for a while I held onto the top rad hose while it started reving up it was just warm then the hose sucked itself right together and as soon as it did that the revs went back down to normal and the hose got hot.
It just kept doing that over and over the hose would be warm suck itself together then the revs would come down and the hose would get hot.
Also while it is reving up the coolant would be going into the overflow.
Anybody ever see this happen before because this is the only lind of truck I have driven for the past 8 years and I have never seen it.

[79coyotefrg]

sucking together means it has a airpocket,   let it idle for a while with the radiator cap off,  make sure the thermostat opens

[bc81bc [OP]]

I let the truck run for like an hour tonight with the cap off and it just kept doing the same thing over and over.

[BLACKDOG]

Try rocking the truck, when it is idling with the cap off, or better yet, park the truck with the side that the rad. cap is on raised.  Then, while it is idling, rock the truck a little.  you should be able to shake the air pockets to the highest point in the system (the radiator cap)

top of the rad was hot on the left hand side of the cap  but not the right side.

 


You might have a problem with the radiator then.  It should be even heat across the board.

[calitaco]

Just curious, how many miles on the Runner and has the motor been rebuilt?  Is it the original motor?

[bc81bc [OP]]

I will try raising the front of the truck tonight to see if that will work.I also put a brand new rad in it when I first got the truck.
There is 148000 kms on it I don't know what that is in miles but the motor isn't even broke in yet for a 22re.

[Cheesemaker]

I'm dealing witht the same issue with my nissan and a newer motor with only 6000 miles on it!  I know that nissans and toyotas have similar problems with poor castings of heads!  That's why I'm dumping my truck ASAP!  I think my motor has a high pressure crack in the exhaust side of the head!  Good luck!

[bc81bc [OP]]

Well I tried putting my truck on a big ramp that we have at work and I let it run for an hour or so it just kept doing the same thing over and over.Rev up push some coolant out then I would top it up and it would do it again and this went on for over an hour.
The bottom rad hose never seems to get that warm and th left side of the rad is hotter then the right.
This problem is driveing me crazy.

[bc81bc [OP]]

Well I finally got sick and tired of screwing around with my truck and went out and bought a HG for it today and put it in this afternoon and that was the problem the whole time.
Just wanted to let you guys know what it ended up being.
Thanks for your help.