NwRunner

I recently rebuilt my 2.7 (including T-stat, water pump, and radiator; all OEM) and ever since Ive been getting some weird temps in my lower radiator hose. The problem is, the temp doesn't rise. I can drive my truck down the highway for an hour, and when i park and check the lower hose its still cold. There is no overheating and the top hose gets to normal temp. Neither me nor vital22re can figure it out, does anybody have any clue whats going on?

DeathCougar

iTrader: (23)

You either have air in the system causing an air lock, a blocked radiator, or a bad T-stat.

YOu said you replaced the radiator with a new OEM radiator? From the dealer?!

Seems like an air bubble to me. Its fairly common on a Toyota. I would pull the hose that goes into the heater control valve (which will allow air to escape), and get yourself one of these:

[IMG]1226593973729__Matco_SpillFreeFunnelwi_PTEN_0.jpg[/IMG]

It puts the radiator as the highest point in the system, essentially.

MudHippy

Just an FYI, the bottom hose is the inlet to the engine block. The top hose is the outlet from the engine block.

Do you really want the bottom hose to be at the same temperature as the top hose?

No, you don't. That would mean the coolant hasn't cooled, via the radiator and cooling fan, and is going back into the engine at or near the temp it came out. Do I need to explain why that would be a "bad" thing?

So, the bottom hose not warming, raising in temperature, relative to the top hose means everything is NORMAL. It being cold would mean you have a very effective radiator and/or cooling fan. No problem there.(It's winter you know, what do you expect?)

If the t-stat weren't functioning correctly/opening properly, or there were some other type of blockage in the cooling system, you would likely be having an over-heating situation. Since your apparently not, then what's the cause for any concern?

Is it taking an inordinate amount of time for the engine to heat up/reach operating temperature? No? Then the t-stat isn't stuck open.

NwRunner

I understand your point but at the same time would a small temperature increase be appropriate even after passing through the radiator? The hose remains as cold as it was before starting the truck. Since i noticed this i have been through 2 Tstats and both boiled at the correct temp.

If anyone with a 2.7 would like to hold their lower hose *cough* and tell me if they are getting the same results as me. I really want to put this issue to bed.

DeathCougar

iTrader: (23)

This is completely wrong.

The radiator will cool the fluid, but not to the point of being cold to the touch. There is either a blockage, or an air bubble.

MudHippy

Completely wrong? Is that right?

Nah...I don't think so. I could be wrong, but my statements aren't necessarily so. Not "completely" anyways. Let's be realistic here.

I'm not saying that there couldn't be a blockage. But a "cold to the touch" lower radiator hose certainly isn't indicative of an air bubble being present. And if the radiator is practically brand new and t-stat's been replaced twice without any change, the likelyhood of a blockage is pretty minimal. Especially so for a blockage at the t-stat itself. 2 brand new OEM t-stats installed, and neither functioning correctly? Come on, give me a break, that's definitely not the problem. UNLESS they were both installed backwards. Possibility?

Now the radiator, though relatively new, could be partially clogged/blocked(somehow?)I suppose. But no over-heating AT ALL as a result? How's that possible with a clogged/blocked radiator, partially or not? Not even a slightly higher than normal operating temperature? Really? That makes absolutely no sense.

And with either potentiality, over-heating(to some extent)would be a far more likely symptom than a cold lower radiator hose.

Here's some examples of what an air bubble in the cooling system will cause.
http://www.supras.com/06/techcenter/display.php?QID=22

http://automotivemileposts.com/garage/v2n15.html

Maybe it's an over-cooling issue caused by a seized cooling fan clutch? That sounds like a possibility to me, if it's condition/functionality hasn't been checked yet. Or does a 3RZ even have one? Maybe not, not my area of specialty.

EDIT: Looks like it does. So yeah, worth looking into IMO.

DeathCougar

iTrader: (23)

Alright, fair enough not "completly" wrong. However telling him there is no problem IS wrong. The lower radiator hose will NOT be cool to the touch. And having air in the system won't always...in fact will rarely....causing a gurgling noise. It causes an air lock.

Again even if the fan was on 100% of the time, the coolant flowing back into the engine would still not be cold, or even cool to the touch. I run BOTH my coolant fans on my race car (electrical) all the time, and both hoses are very warm by the end of the race. Same thing goes for cars before they used fan clutches. The fans ran ALL the time. A cooling system isn't designed to completely cool the motor down, just pull head from the engine and radiate it to keep it cooler.

NwRunner

I assure you the tstat isnt backwards, i dont even think they will fit that way. DC i bled my system through the heater control valve for about the 50th time this morning and nothing has changed. When i redid my head i flushed the coolant lines with cleaner and the water came out relitavely clean, i dont suspect any blockage anywhere nor is there a reason for a block.

The truck runs like a dream, maybe i should just leave it be? Its still very annoying not being able to figure it out though.

Edit: Fan clutch isnt seized either

bulletbikeguy

I'm having a similar issue with my 96. It's not able to keep up with the Montana cold. If I sit the heat rises but when I'm in motion the vents blow colder and colder. Mind you that the temp gauge isn't showing the temp drop all that much but I can feel it through the heater! Very, very annoying!

NwRunner

My gauge doesn't show any fluctuation, and my heater still burns the air like every other yota ive owned. I imagine Montana cold mine may do the same, but it only gets about 20F at the lowest here.

Im thinking about installing a temp guage so i will be able to monitor whats going on, but with such great differences in temp im not sure where to put it...

Gerdo

Mine is a 3.4 but even in the hot weather my lower radiator hose is basically ambient temperature.

Will Clift

my 96 2.7 3rz does the same thing top is burning hot and the bottom one is literally cold

75w90mantraN

Although this thread is 7 yrs ago, it seems unsolved. If there's no temp gauge fluctuations or stuck t-stat, if you're able to get warm air through the vents, may be alright. If anything, it may be some restriction inside the heater core...someone did mention it blows cold during drives. Deathcougar did mention the possibility of air bubbles. So bleeding the cooling system is a cheap way to troubleshoot. But the heater core may need to be looked at. That's my thought.