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90xj06
November 13th, 2017, 11:57
so as the cold air moves in again. i am left with marginally warmish air.
i also notice that the temperature gauge fluctuates and im guessing thats from when the thermostat opens.

i was reading this http://gojeep.willyshotrod.com/HowtoRadiatorRestrictor.htm

could this be an cause of the no heat issue?

what are your thoughts on this?

dan1977p
November 13th, 2017, 12:48
Before trying to alter how your cooling system works, you should confirm your heater core is still in good shape, blend door is doing it's job and there is no air in the system.

Usually, this is a heater core issue, though.

90xj06
November 13th, 2017, 13:35
I did look into the blend door and heater core. i have an 88 and can hear the blend door opening and closing. and can tell when its switched. and i did flush the heater core twice now. and no gunk comes out and its flowing pretty good. i have a digital thermometer in the center dash and i got about 118 today and it was about 40 out today. on my hours drive to work it still ends up cold in the cabin.

i feel with the renix cooling system the coolant would just go through the tank and skip the heater core.

Green XJ Jeep
November 13th, 2017, 18:03
Is the vacuum valve opening up?
When was the last time you put a thermostat in it?

90xj06
November 13th, 2017, 18:49
ill double check the vacuum valve. it is newish.
i replaced the thermostat last year when i swapped this engine into this jeep.

lawsoncl
November 13th, 2017, 21:39
It's been quite a while since my 89 had that stupid crumbly plastic vacuum valve. As I recall it was a screwy design that let some coolant bypass the even when it was open. When I converted to the "closed" style used in the later Jeeps and plumbed directly to the heater core, my heat significantly improved. I measured 140*F air from the vent on high in 30-degree weather.

ehall
November 14th, 2017, 06:20
What does the temperature gauge show? Normal to get a ~50 degree drop in temperature from the head to the heater vents. If the engine isn't fully warmed up you won't get good heat.

Feel the heater hoses with your hand. Top hose from the thermostat housing should be hot and consistent. Lower hose return to the pump should be cool when heat is running, and same as top hose when not.

90xj06
November 14th, 2017, 15:35
Today was not as bad. It was 45 out with engine temps between 175-182 and center vent fan on 2 temp 120. It wasn't as cold and raw out today.

dan1977p
November 14th, 2017, 16:33
Why is your engine temp only getting up to 182?

ehall
November 14th, 2017, 19:27
185 tstat? put a good quality 195 in there

90xj06
November 15th, 2017, 06:17
for the most part it sits around 175. i wonder if i got the 160 one by accident. any particular brands you recommend? me and the thermostat housing are sworn enemy's.

dan1977p
November 15th, 2017, 06:33
I never had any issues with my 195* duralast tstat. If you're having issues with keeping the tstat in place when mounting the housing, you can apply a thin layer of rtv to the tstat and mount it on the inset part of the housing or the head (I forget which side has that right now). Just be careful to not block the weep hole in the tstat and use as little as you have to just to make sure it doesn't move. And if the housing isn't flush before you tighten the bolts, the tstat isn't in the right place and you need to restart from step one.

ehall
November 15th, 2017, 07:30
Stant Superstat is my go-to, never had a problem with them. Mopar made a slightly different model for the last couple of years (buy one for a 2001 XJ), expensive but it works well and has a built in breather to let air out.

JeepNoob
November 15th, 2017, 21:25
Stant Superstat is my go-to, never had a problem with them. Mopar made a slightly different model for the last couple of years (buy one for a 2001 XJ), expensive but it works well and has a built in breather to let air out.

Agreed. I've heard some bad stuff about Stant stuff here, but never had a problem with the Stant cap or 195-degree T-stat I put in my '96. In fact, when I first bought it, I flushed the coolant not long after and installed the Stant stuff while I was at it. 2 years later when I flushed it again, I re-used both.

90xj06
November 25th, 2017, 18:29
so i swapped out my thermostat today. it was a 195 t-stat. i did swap it out with a new 195 duralast one. i bled the air from the t-stat housing as i have a later one now. i also swapped the ECU temperature sender.

today it was ~60 out and i got the temperature to stay around 182-195. now to see how it does when its cold out.

90xj06
November 28th, 2017, 06:38
today was 20 out engine temp stayed around 179-182

i did notice when i switch from vent to heat my thermometer got stuck in the blend door and the heat coming out of the vents was a few degrees hotter.

does the heat to vent do anything other than move the blend door?

ehall
November 29th, 2017, 07:48
does the heat to vent do anything other than move the blend door?
nope

sinat01
November 29th, 2017, 14:38
Just because the blend door is moving doesn't mean it is doing its job. that was part of the issue I had with my heat was the old blend door wasn't sealing up and letting cold air in. Check out Heatertreater, they make steel blend doors for XJs

90xj06
December 7th, 2017, 09:51
so i went through the FSM and apparently when the selector is in the vent postion the heater water valve is CLOSED. this would cause the heat to be sucky. in all other positions the valve is open unless in full cool mode. this explains why the heat was at 144 in bi-level a/c mode. i might go cap the vacuum line for the valve until spring.

90xj06
December 8th, 2017, 06:32
Just because the blend door is moving doesn't mean it is doing its job. that was part of the issue I had with my heat was the old blend door wasn't sealing up and letting cold air in. Check out Heatertreater, they make steel blend doors for XJs

does this still apply to an 88? im pretty sure i have steel doors but the sealing could be an issue.

also, in 91 they changed the heater controls to allow the water valve to operate in all modes. and i have one from a 93 so my valve does work.

so any one with a renix and bad heat performance in vent mode might want to give this a check.

dan1977p
December 8th, 2017, 08:32
Most also remove the useless heater control valve so water is flowing through the heater core all the time like in the newer models.

90xj06
December 8th, 2017, 11:10
i want to try and avoid removing it.