kscotese

I have a 95 XJ with 2.5l 4x4.

My heater control valve was leaking so i replaced it and the new one leaked. I looked on the forums and it looks like that is a common problem and most people just bi-pass the valve entirely. So i did that.

Now that i have done that it seems to be running colder (about 10-15 degrees). I have a digital temperature gauge that is in the heater hose right after it comes out of the thermostat before going into the heater core.

When i had the heater control valve in, it would warm up to 195 (i have a 195 thermostat in it)and then stay there, no matter if i had the heat on or what.

No it warms up to about 170 and than after about 20 mins of driving it will get to 180ish.

I don't get it. How is it any different that driving with the heat on? All that is happening is that the coolant is following through the heater core all the time, but the thermostat should still be opening at 195. Why is it running colder? This happened right after i bipassed the heater control valve.

Thanks

mmattern1985

I just did the same thing in my 89 and I can't figure out anywhere if this is a good thing or bad thing. I hope im not going to mess anything up

Copytech

The heater control valve doesn't stop the water flow in the line it just diverts to either the heater core or back into the cooling system. so bypassing it would not cause a problem.

VTJeep

id guess that by bypassing the valve, you offset the temp, somehow... but as far as causing issues from operating outside of a normal and/or recommended range is unlikely. you would really have to get that thing running cold for an extended period of time before you would cause issues. on that note, running a separate tranny radiator is never a bad idea as the radiator serves both the engine and tranny, it can easily overheat in the right conditions, like a hot day playing in the sand... at least, thats what prompted mine.

mw6886

I just changed the coolant in my cherokee and water pump and thermostat.Since the heater valve does'nt completely shut off the flow through the heater core i do'nt see how the temp would change.I did discover when replacing the water pump that the heater hose connected to the water pump extension pipe it will circulate through the heater core as soon as the engine is running..this is because the hose that is connected to the thermostat housing circulates through the engine because of a small opening in the housing and engine so if the thermostat gets stuck it will still circulate..

djb383

Knowing your ambient temps would help a little. Any vehicle runs cooler in cool/cold ambient temps. The heater core is a small radiator so it's going to remove heat from the engine coolant. We also use a digital coolant temp display, coolant constantly circulates thru the heater core on ours ('98) also. Cool/cold weather, we can see coolant temp rise/fall slightly depending on dash blower fan speed, when using the heater. The longer u drive in cool/cold weather the more coolant temp will stabilize, as you have noticed. Probably a non-issue come summer time heat.

mmattern1985

I figured it wouldn't do any harm but I think I should be fine the heater just wont work but I live in phoenix so its not like ill ever use it

lurk520

The only reason your heater wouldn't work is if you bypassed the heater core itself. Your heater will still work with out a control valve.

mmattern1985

By bypassing the heater control valve it cuts the coolant off from entering the heater core. All I did was tie the valve closed on the control valve and it stopped over heating but as soon as I open that valve it overheats in minutes

mmattern1985

I had to close it manually because for some reason the vacuum line that opens and closes that valve doesn't work.

lurk520

huh, mine is bypassed but the coolant is still routed through the heater core. Guess it depends on how you do it. Well my control valve isn't even under the hood any more.

mmattern1985

I didn't really bypass it. I just tied the little valve shut that vacuum actuated. It is usually always open and it allows coolant to flow to the overflow bottle and also through the heater core when the vacuum acutes the heater control valve it closes the valve and only allows coolant to go straight to the overflow bottle