Do you have your thermostat in the correct direction? Does it still overheat with the thermostat removed?

 

I would just run without a Tstat.

 

Alright, thermostat is out, and the lower rad hose is still cold.....???

I ran the car by driving it around for about 20 minutes and it didn't overheat. I even disabled the cooling fans to see if it would overheat but it didn't.

Anyway, I felt the lower hose, and the first 2-3 inches are warmish, and then it gets cold for the rest of the length. I can obviously squeeze the hose and with the bleeder screw off, coolant goes spewing out...

I know I am thinking blockage now, but I literally just flushed everything out and nothing was blocked. I ran a hose through the block and it flushed it nice and clean, and the radiator and hoses are brand new...?

Any ideas?

P.S. I get plenty of flow through the heater core and such, so I assume the water pump is working.

 

What's your ambient temp?
Stock KA?
You heater get warm?
You do realize that's what a bigger radiator is suppose to do right? Keep your coolant cool.
Take off the bottom hose and look inside?
Squeeze where it feels cold to see if anything is there?

I don't see what the problem is if your not overheating?

 

Yeah when I had my koyo rad my temp was always pretty low.

 

My thermostat days are over. Get a little too hot and it sticks close next time. Crap ass.....

 

Current air temp is about 29 F, so, it's quite nippy. Snowed yesterday. Nothing like Hawaii, (born in Aiea).
Stock KA, 95,000 miles on it.
Heater gets slightly warm but not nearly as hot as it used to, I am afraid the sheer capacity of the radiator was keeping the car cool for the first 20 min.


So, I took it on a longer drive 30 min or so and warmer at 50 F, because I realized the top hose was pretty hot but the bottom was really cold and I just may not have heated it up enough the first time, and it started to overheat again. Felt the bottom hose and it's still cold but the top was very hot.

This is all without a t-stat... Kind of lost right now.

 

See that's why. You have a 3" Radiator on a Stock KA with Temps below 80. Even with how warm it is here I sometimes go back into warm up/high idle cause the coolants cooling off too much.

Honestly if nothing's going wrong besides it being cold I don't see any problem.
But I would advise you put a new thermostat or atleast a good one in to help get the engine up to temp.

 

Well that's the problem, it's overheating right now. I tried burping the system a few more times, but no air came out. Seems like there's no flow to the radiator, it's really strange.

I am going to yank the intake off and recheck the heater hoses to see if one has collapsed for something.

Is it possible for a collapsed heater hose to stop flow to the radiator? And is it possible the radiator cap is somehow overpressurizing the system? THe cap is really really tough to screw and unscrew.

BTW, thanks for the help.

 

High pressure caps help keep it from over heating by keeping more pressure to up the boiling point.

What's new on the car. Like what's been changed?
How do you know its overheating?

 

The bottom hose is always gonna be cold or coldish. The coolant goes in from the bottom and out the top.

 

The bottom hose is always gonna be cold or coldish. The ka's have a reverse flow system, coolant goes in from the bottom and out the top.

Ummm wut?no. hot coolant from the engine goes into the radiator from the top and gets cooled then the cooled coolant goes out the bottom hose to gather heat again from the engine

 

^ Thats what i just said... It goes in from the bottom hose gets the heat from the block then the head and takes it to the rad!


Edit: i see my mistake on that.

 

I know it's overheating because the temp gauge goes to 3/4 of the way up before I pull over (I know they are weighted gauges), and the coolant starts to boil.

Takes maybe 15-20 min of normal driving to get hot, and the heater doesn't seems to make it drop any more than it heats up. I crank it to "4" and it still rises.

 

Not sure if this will help you much but I had an 80s camero. Put a racing rad in it. Bigger core and such. In the colder temps I had to run without a T-stat. One side was to cold and the other was hardly at temp for it to open. So it mostly seemed that it was over heating. In the summer over 85 constant temp I would run a T-stat so what's in the rad would have a chance to cool.
My KA I have a duel core koyo and I haven't had any issues without a T-stat winter or summer. I also have never tried with one in. I just stuck one in to see what happens. But I'm sure I'll pull it out soon.

 

i have the same problem with my ka, it was overheating so i flushed, new water pump, thermostat, ext. with no thermostat the top hose is hot and bottom is cold, i can watch the coolant flow from bottom to top, but the thermostat housing is on the botom hose. so how can the thermostat open its on the wrong hose?

 

Best thermostat

Very informative thread.