TTORA Forum banner

1 - 20 of 20 Posts

·
Registered
Joined
·
1,657 Posts
Discussion Starter #1
Is it possible at all?

So was wondering if there was a trick to quickly replace the thermostat without having to drain the whole thing.

How much coolant would it spill out if disconnecting hose from old thermostast without draining radiator?

Is it worth the try? Too messy?

Parking on the street here in NYC, is fricking cold outside, not a lot of room to wrench, truck is only blowing cold air inside. Would hate to take it to a shop, end up paying few hundred $$ (NY rates:eek:) and waste an entire afternoon waiting for such a simple thing.

Specs: 3RZ-FE blowing cold air in 35 deg New York weather:eek:

Checked lines at the firewall and they are both hot. So I assume the culprit is the thermostat stuck open. I hope the heater core is not toast:(

Thanks.

-ben90
 

·
Registered
Joined
·
757 Posts
No, the thermostat cannot be changed without draining the radiator. But honestly, it's very easy to drain with the stopcock on the bottom right of the radiator. Once drained, the whole thing will go fast as the thermostat is VERY easy to get to.

Buy an OEM thermostat and O-ring.

Also, before doing this, make sure the thermostat really is the problem. Does your temperature gauge run in the middle, or is your engine not heating up altogether? If it's not heating up than the thermostat may be stuck open. Also make sure your not just low on coolant?

Check the valve on the lines going through the firewall to the heater core. The valve opens only when the temp dial is turned to hot, and if yours is stuck shut or the cable that controls it is malfunctioning, this would produce no heat.

Good luck..
 

·
Administrator
Joined
·
18,267 Posts
Check the valve on the lines going through the firewall to the heater core. The valve opens only when the temp dial is turned to hot, and if yours is stuck shut or the cable that controls it is malfunctioning, this would produce no heat.
Check this first! I've seen the cable come off the valve before and its a 1 min fix.

The thermostat is right up against the block on the driver side where the lower radiator hose attaches. You can use a clamp to pinch the hose while you remove it, but you'll still lose some coolant out of the block.
 

·
Registered
Joined
·
5,467 Posts
Hey Ben! It's been a while since we talked last!

Anyway, as the guys mentioned above, I would venture to guess that you've got a problem with the valve to the heater core. Even if your thermostat was stuck open, you'd still get some kind of heat after the motor is warmed up.
 

·
Registered
Joined
·
1,657 Posts
Discussion Starter #5 (Edited)
Hey Harold, great to hear from you man!

So I have to drain the radiator. Well, i was hoping there was a shorcut. Lazy me :p

I went outside to double check, and the temp gauge goes up as usual. Just not hot air coming through the vents.

So need to check that release valve again at the firewall as tacoma4life and showstop mentioned, and/or replace the thermostat.

Let's see how can I pull that one off at the parking lot at work:eek:
 

·
Registered
Joined
·
1,657 Posts
Discussion Starter #6
update: well, seems like the culprit was that release valve. The cable seemed a little loose, so put it back where it should be.

What a simple fix:rolleyes: (for now at least)

Thanks guys.
 

·
Registered
Joined
·
390 Posts
Hey Ben! It's been a while since we talked last!

Anyway, as the guys mentioned above, I would venture to guess that you've got a problem with the valve to the heater core. Even if your thermostat was stuck open, you'd still get some kind of heat after the motor is warmed up.

I think I have this prob with my truck. I get heat but its not that hot. Seems to be worse when its really cold out.
 

·
Registered
Joined
·
1,657 Posts
Discussion Starter #12
Glad you found it! Man, I don't think I could live in NYC. I need my own garage to work in!
I hear you! It's very frustrating not having enough room to even do basic maintenance stuff. Actually, having a garage of any type is a rich man's luxury anywhere around here:D

Right dead in the middle
Sounds like you had the exact same problem like me. I had a friend turn the temp dial knob inside the cab from hot-cold positions several times. Found that the cable was a little off (loose). Try that and see what happens. Did you check that the two lines by the firewall are hot?

We'll, the thermostat is doing the job correctly. Seems like it's either the valve or you may even have air trapped in the heater core.
If that's the case....which could be....what is the best way to get the air out?
 

·
Registered
Joined
·
390 Posts
We'll, the thermostat is doing the job correctly. Seems like it's either the valve or you may even have air trapped in the heater core.
I thought so too, about the air that is. I brought it to operating temp raised the front end in an effort to "burp" the system but that didnt help. I didnt think to check the valve though. I'll check it out tonight after work.
 

·
Registered
Joined
·
5,467 Posts
If that's the case....which could be....what is the best way to get the air out?
Park the truck on an incline (front facing up), take off the radiator cap, start the truck and turn the heater on full blast, let the truck warm up, continue adding water until all the bubbles are gone.
 

·
Registered
Joined
·
35 Posts
Also, make sure your coolant overflow setup is working correctly.
If the cap does not have a good seal on the outer seal, it wont draw in coolant when the engine cools down. When it's hot and has air bubbles, the coolant that does splash inside the head will flash to steam and blow some coolant out and some air, when it cools, the steam returns to liquid and creates a vacuum that will draw coolant back into the system if the overflow tank is working correctly. Since it's getting to be winter up in the frozen north, add some antifreeze to the water in the overflow tank, 50/50 and it wont freeze :)

I had my V6 open the other day, had to pull the top hose to inspect the timing belt, so I partially drained the radiator. After re-assembly, I filled the radiator with the drained coolant, Idled the motor a bit and filled again, still had about 1/2 a quart left, put that in the overflow, the next day after driving to work, the overflow was back to about 1/2 full, it had been 3/4 full.
 

·
Registered
Joined
·
19 Posts
I am having the same issue. The temp gauge is right in the middle, but my heater is blowing COLD air not even a little heat. The thread seems to indicate thermostat is working and there might be another issue. I will try to burp the system. If that does not work can anyone else offer another suggestion?

This makes since I had to change my radiator this fall, but the heater worked for several months before this happened.
 

·
Registered
Joined
·
19 Posts
Can you explain this part...

Check the valve on the lines going through the firewall to the heater core. The valve opens only when the temp dial is turned to hot, and if yours is stuck shut or the cable that controls it is malfunctioning, this would produce no heat.

dg
 

·
Registered
Joined
·
2,903 Posts
It means exactly what it says.

Your motor makes heat. There's a pump that pushes coolant in a circle.

The coolant gets hot in the motor, then it goes out to the radiator to be cooled, then goes back to be heated in the motor again.

There is a thermostat that opens and closes based on temperature. It stops the flow of water to the radiator until it warms up to a specified temperature, then opens and closes as needed to maintain that temp.

Your heater uses the hot coolant to warm the cab.

There is a smaller circuit that bypasses the thermostat (It flows all the time if the valve is open) then goes through a control valve, then through a smaller radiator inside the cab, then back to the motor.

The coolant in the heater circuit is pushed by the same water pump that the radiator uses.

So, when the heater control valve is open, hot coolant warms the cab.

It's not complicated.
 

·
Registered
Joined
·
3,596 Posts
In my 02 truck, there is also a servo motor under the dash that controls the cable that opens/closes the valve. I've had the arm on this servo motor break off and have the same symptoms as above. So if the cable at the valve looks ok, go under the dash on the passenger side to see where it connects to the servo motor.
 

·
Registered
Joined
·
1 Posts
No, the thermostat cannot be changed without draining the radiator. But honestly, it's very easy to drain with the stopcock on the bottom right of the radiator. Once drained, the whole thing will go fast as the thermostat is VERY easy to get to.

Buy an OEM thermostat and O-ring.

Also, before doing this, make sure the thermostat really is the problem. Does your temperature gauge run in the middle, or is your engine not heating up altogether? If it's not heating up than the thermostat may be stuck open. Also make sure your not just low on coolant?

Check the valve on the lines going through the firewall to the heater core. The valve opens only when the temp dial is turned to hot, and if yours is stuck shut or the cable that controls it is malfunctioning, this would produce no heat.

Good luck..
Actually, you can change the thermostat in some trucks without draining the radiator. Start with a cold engine. Release the radiator cap to bleed any residual pressure out the system. When you disconnect the hose from the thermostat, a little fluid will leak out, but not much. Keep the hose end pointed up as much as possible. When you reconnect everything, start the engine and add back the little that spilled. Just did it this morning on my 04 4Runner, worked like a charm.
 
1 - 20 of 20 Posts
Top