Kelly00127

Take a look at this youtube video. I know your Toyota does not have a bleeder valve for air, but his method should work. If it doesn't I'm guessing something worse. If the link does not work search youtube for
How To Bleed A Cooling System - EricTheCarGuy

I hope this helps you.

http://www.youtube.com/watch?feature...&v=zUpXgAJ1gjU

Koso1985

I know the block, heads and headgaskets are all good since it flows GREAT with no thermostat.

Kelly00127

If you know it works without the thermostat, then it has to be the thermostat. Or with the thermostat out, there is no pressure (free flowing) so it does not draw air/leak coolant? As a precaution I would pressure test the system to see if it is drawing/leaking air/coolant somewhere. Whatever you find, I would love to know the answer.

Koso1985

Thanks Kelly,

I did a pressure test, and it held 13-14 PSI no problem, did not drop off at all.

I have had two master techs also come look at this, and they are dumb founded what could be going on. This is the thermostat that I have in the truck right now:

Kelly00127

I am at a loss. I'm guessing the answer may lay with the owner of the vehicle, if they did anything. Maybe they disconnected a couple of the coolant hoses (heater core) and mixed up which way they go. But I'm not certain that would cause the overheating.

Koso1985

Yeah, the owner has only owned it for about a month, and it ran good tell the blew the gasket.

I don't know if the lower hose to the radiator if it was crushing it self would cause this or not?

Koso1985

Update:

I put a new sending unit for the gauge, still the same.

Tomorrow I'm going to do a leak down test and see if its pushing any air into the cooling system from cracked heads or something.

I'm really starting to run out of ideas

BMcEL

It's definitely getting air in the system somehow. Usually small amounts are overcome by an air bypass in the thermostat but if removing the thermostat is the only thing that fixes it, there's a lot getting in there.

I'm still thinking head gasket or cracked head.

Koso1985

Yeah, I'm thinking there is worse problems :/

Koso1985

One thing I did notice, the upper intake manifold dose have a vacuum leak, you think this would cause the overheating problem?

Koso1985

I did a leak down test, and nothing came up, not even 5% leak down.

So back to the drawing board.......

jerry507

To me, whenever I see a problem that is solved by running the heater I immediately think the system isn't actually cooling ENOUGH through the radiator. The heater can actually dissipate quite a bit of power. The fact that you turn the heat off and it slowly starts to creep up would seem to say that you're not pushing enough power out the radiator and the temp is building slowly. The gauge responds rather slowly because of the sender, so it's even slower than you're seeing.

I'd still say your block is plugged up somewhere and you're not getting enough flow. The block may be AFTER the heater core hoses, so you're still getting full flow to the heater. That's my guess...

Pickup91

Were you ever able to figure this one out? I would love to know the final diagnosis.

Boruskarloff

Got a customers 95 4Runner here complaining of shifting out of OD when it started to get colder here in WI.

So I check the simple things first: thermostat stuck open allowing the engine to cool below operating tenp where OD kicks out. Well the thermostat was missing when I took the housing off.

Put thermostat in, 1/16 hole at 12 o'clock, bled system, coolant moving on top of rad with cap off, good heat and temp stays right in the middle with cap off.

Put the cap on and go just down the street and it gets super hot....ok I got an air bubble I think.... Bleed again.... funnel full and run truck and it's just about spewing out of the funnel.

Ok bad thermostat? Test it in boiling water and it opens.....ok put it back together with no thermostat again and it run perfect, no cooling issues and no pressure spike.

So I stumped right now too??? And both of my friends who are also master techs are stumped too! What ended up fixing your issue???

I can't see it being a headgasket issue here because there is no white smoke, no coolant loss, no misfires when cold start, no water in oil or milky oil....and the truck has run cool for customer since he bought it 20k miles ago (whoever had it before must have removed the thermostat)

Gonna try a Toyota oem tstat tomorrow but I doubt that will help as it didn't help you!

-Travis

millball

Take the top radiator hose off at the radiator, loosen the clamp at the water neck and rotate the top hose up to vertical. Fill thru the hose until coolant runs out of the radiator top tank. (I assume that this is 3vze 6 cyl.)
Many of these radiators have a little dam behind the top outlet that makes it look like the system is full when its not.

Boruskarloff

Thanks for the reply, I've read that way to do it somewhere before too. And yes it is the 3vze v6.

I figured my funnel at the radiator being the highest point in the system would be good enough. And based on simple theory should fill the same way as you are describing.

Idk your method is worth a shot anyways. Guy needed his truck back so I sent it without a thermostat again because I'm waiting on the oem one. So Monday it'll be back and I'll try some more things

Boruskarloff

K truck came back today, Installed oem Toyota thermostat, filled system through upper rad hose like suggested above. Same result with rising temp into dangerous levels and unreal pressures at top hose, top hose hit bottom hose cold. Tried to bleed it with a no spill funnel again (which is definitely the highest point in system) no change.

So I took thermostat out while car was still warm and the tstat was open.

I'm no looking into testing for exhaust gas in cooling system and pressurizing the system to find out if I have a head gasket issue here, only other thing is something is clogged up (block/ radiator ??)
I won't get to test this for another couple weeks as the customer took the truck back again without tstat, and will be out of town for two weeks against my better judgement!

I will report back when I find out wtf is going on here.

Tyler McAfee

No one reported back...smh

Co_94_PU

iTrader: (-1)

Well no news is good news sometimes.

My suggestion is to pull the heater hose from the heater valve on the firewall. Then fill thru the radiator till it starts running out that hose on the fire wall. This should minimize any air pockets, since its the high spot at at the far side of the input.

Worth noting. If the engine is cold and you crack the radiator cap and get air flowing into the overflow, it is a very good sign there is exhaust pressure in the coolant system.