Not enough heat with Champion 3 Row Radiator

[cruiser54]

With an OEM 195* thermostat, no mechanical fan and both electric fans off, it is difficult for my XJ to get above the 195* thermostat setting at highway speed with the cabin heater turned up high in ambient temperature below 50*. I will however get up to 200+* in slow moving city traffic.

I think to OP may have a bad thermostat in addition to a very efficient cooling system. It could also be a non functioning valve on the fire wall in the engine compartment i.e. not enough vacuum when the engine is under load to keep the valve fully open thus not enough hot water to heat the cabin.

I always ditch the valves. But it's easy enough to check with your bare hands. Is the temp different on either side of the heater hoses at the firewall or the valve?

 

[1990JEEPXJ]

Thermostat is NOT affected by ambient temp at all, but COOLANT temp.

I know, but ambient temp effects coolant temp, to an extent. If it's 2 degrees outside will the motor be incapable of getting up to temp? Even if the thermostat is open?

 

[vt98xj]

keep in mind that Thermostats don't go from fully closed to fully open instantly but start to crack open at a lower temp allowing some coolant to flow in the system. They are fully open at the temperature that is marked on the valve.

 

[yossarian19]

I've driven my Jeep home at 20 degrees *below* zero. Heat worked just fine.

 

[cruiser54]

I know, but ambient temp effects coolant temp, to an extent. If it's 2 degrees outside will the motor be incapable of getting up to temp? Even if the thermostat is open?

I think you mean closed..

And no, it should get up to temp.

You need to read this:

http://auto.howstuffworks.com/cooling-system8.htm

 

[Digger87xj]

I know, but ambient temp effects coolant temp, to an extent. If it's 2 degrees outside will the motor be incapable of getting up to temp? Even if the thermostat is open?

First, you must understand that the thermostat is there to restrict coolant flow to the radiator until the coolant reaches a specified temp. A 195* 'stat should keep a properly running engine at ~200* or so. It opens and closes constantly allowing more or less flow through to the radiator.

A stuck open or missing 'stat will allow coolant flow through the radiator all the time, never allowing the engine to reach operating temp.

So, yes, an engine that has a properly working thermostat even at 2* will easily get up to temp.

 

[1990JEEPXJ]

A stuck open or missing 'stat will allow coolant flow through the radiator all the time, never allowing the engine to reach operating temp.

So, yes, an engine that has a properly working thermostat even at 2* will easily get up to temp.

I know how a thermostat works. I just find it extremely hard to believe that an engine cannot reach an acceptable running temperature with a thermostat stuck open. That's what I don't understand. If an open thermostat allows an engine to run at 210, how will one that is stuck open not allow it to reach 210? Hence I asked if the temperature on his gauge was verified as well as the flow of coolant through the heater core.

 

[Jeepguy03]

I know how a thermostat works. I just find it extremely hard to believe that an engine cannot reach an acceptable running temperature with a thermostat stuck open. That's what I don't understand. If an open thermostat allows an engine to run at 210, how will one that is stuck open not allow it to reach 210? Hence I asked if the temperature on his gauge was verified as well as the flow of coolant through the heater core.

If the thermostat is stuck open, the coolant does not stay in the engine long enough to heat up to temp before going back to the radiator. It may warm up slowly to 160*, but it might never reach operating temp. With the stat stuck open, the coolant is constantly flowing to the radiator no matter what temperature it may be. A thermostat allows coolant to flow through only after it has reached a certain temperature. In colder weather, the radiator becomes even more efficient, so the thermostat becomes even more important.

 

[Digger87xj]

keep in mind that Thermostats don't go from fully closed to fully open instantly but start to crack open at a lower temp allowing some coolant to flow in the system. They are fully open at the temperature that is marked on the valve.

No, the stamped temp is when it begins to open and allow coolant flow.

I know how a thermostat works. I just find it extremely hard to believe that an engine cannot reach an acceptable running temperature with a thermostat stuck open. That's what I don't understand. If an open thermostat allows an engine to run at 210, how will one that is stuck open not allow it to reach 210? Hence I asked if the temperature on his gauge was verified as well as the flow of coolant through the heater core.

I see your confusion.
As I corrected the poster above, the thermostat only begins to open at the stamped temp. In a correctly working cooling system, the thermostat never completely opens.
So, in an engine that consistently stays at say, 210*, the thermostat is allowing just enough coolant flow through the radiator to keep an even temp. If the engine creates more heat, the stat opens more to allow more flow, and closes down and slows flow as engine temp decreases.
The radiator should be overly efficient for the engine it is cooling. so, with no thermostat, the coolant flow is never checked and is overly cooled and the engine never reaches operating temp.
There are of course many variables that change that statement... a plugged radiator, either airflow or water flow, or a mechanical fault of the engine such as a leaking headgasket.

 

[yossarian19]

For evidence in support of the above;
In Utah I drove about 200 miles from Salt Lake City to Loa, parked the Jeep for a week and got back in to drive home. It was under 10 degrees F when I started home.
The engine never got above 100 degrees operating temp. The gauge never moved - at all. No heat. Froze my ass off for five hours through a light snow, IIRC.
Replaced the thermostat a day or two later... voila - same cold-ass winter, but the heat now worked and engine got to 210 no problem.

 

[Ben824]

You've got a wonky thermostat. A Stant SuperStat?

I work at a dealer so I will probably just go that route for a t-stat for cost savings and to see if that even fixes the problem.

 

[Ben824]

Have you confirmed temp with a IR gauge?

No I haven't but I am running a two stage switch to trigger my new fan and it comes on right when expected and the gauge confirms it is coming on at the right temp.

 

[Ben824]

Sounds like a cool setup. Are you running the two OEM electric auxiliary fans with the stock alternator?

I am running two OEM fans with a replacement alternator from O-Reily's that is supposed to be rated at 117 amps. The factory was supposed to be 90 amps.

All in all the system runs great but between the fans in the summer running full blast on the hottest days and my sub hitting hard, I need a better battery.

 

[Ben824]

Ben824 did not say what year his XJ is. :eyes:

You are right! What a newb move. I have a 97.

 

[cruiser54]

I know how a thermostat works. I just find it extremely hard to believe that an engine cannot reach an acceptable running temperature with a thermostat stuck open. That's what I don't understand. If an open thermostat allows an engine to run at 210, how will one that is stuck open not allow it to reach 210? Hence I asked if the temperature on his gauge was verified as well as the flow of coolant through the heater core.

It's not totally open at 210*

It's constantly moving and adjusting.

 

[Ben824]

For the record I have a 1997 that will reach operating temp sitting at idle. When I am driving along and have more air flowing across the radiator, the temp drops way down in between the 0 and 210

 

[Digger87xj]

thermostat in faulty then.

 

[cruiser54]

thermostat in faulty then.

Yup. Lots of parts out there now being made overseas by WunHungLo and his buddies.

 

[Ben824]

Ok finally solved my over cooling issue. Picked up an OEM Mopar thermostat and gasket, I work at a dealer so I got them for a reasonable price, and got them in yesterday and so far so good! Heats up nicely hangs out between the mark before 210 and 210. I have heat again!!!

Here is what I found. The thermostat I bought before I got from O'Reilly's and the guy called it a fail safe. Well I discovered why. It has these special tabs that hold it open if the thermostat opens up so much as in an overheating situation. From that point forward it is forceful held open. I even tried to see if I could get it close and I could not. So the Thermostat was definitely my problem.

Thanks for all the help guys!

 

[cruiser54]

Told ya!! LOL. I went through this crap with Stant stats on 3 Jeeps.