mr white

It only takes a couple hours if you aren't trying real hard to get it done. i'm pretty sure I got at least 5mpg probably more by replacing the cracked header. It was a very noticeable difference.

VTJeep

ok.. first off, as stated, youve got the WRONG stat!! not letting your vehicle operate at nominal temps is bad for it, whether it be too cold or too hot.

~get rid of that damn 145* tstat!! now!!
~replace it with a 190*
~flush the hell outta your system.. while your at it, flush and back flush the heater core. you mentioned the heat not working well, this will help..
~it sounds like your water pump is suspect too- over time the impeller wears down diminishing the vehicles ability to cool itself without air being forced thru it (like when driving)
~might be worth a new radiator, too.. i know its starting to add up, but i wish id done mine when i did all of this recently (water pump was no mas) ya dont need a fancy 3 row oem will be just fine.
~for just a few more bucks add a tranny cooler too..

mr white

I don't think the heat is working well because he has a 145 tstat.

ChilliXJ

I changed the water pump with the tstat 4 months ago. Ive ordered a new tstat now

Cherryokee

Hi ChilliXJ,

Let me offer a tip that might save you some moolah - and maybe a tick of MPGs too.

At the bottom of your original post you mentioned a cheap battery and 10V charge voltage indication. Your battery may not be at issue - unless you have already proven a poor state of health. Instead, there may be a real low-voltage condition that's preventing optimal operation. FYI: I also had indications of a low charge voltage in my '99 last week. I saw the "check gauges" lamp (but the gauge test passed) and the diagnostic code "P1682" when scanned, but my battery is young and premium. Since charge voltage is regulated within the ECM, I pulled and cleaned the connectors to my ECM, cleaned then re-attached ECM mounts and body/block ground terminations and all charge conditions/indications returned to normal.

This was a simple no-/low-buck approach to resolving what could have become a few hundred bucks worth of pain and it worked. I hope this info helps you.

BTW: What new spark plugs did you use?

ChilliXJ

Wheres the ecm? I used the sparkplugs thats recommended on the sticker under the hood, champion copper plus i think they were

ZINGGG

Agreed that your poor heat and possibly some MPG loss is due to the low thermostat.

But. You will have to drain the cooling system to get to the thermostat anyways so it's a good idea to flush and backflush the heater core, as VT mentioned.

V8XJDavid

We all hate you.

ZINGGG

We sure do

VTJeep

Haha, 24? What with a broke gauge? Haha, just messin.. That's damn impressive!!

235/75's on ~2" and I'm like 16+/- for mostly rural/town driving. Interstate it def goes up 2 or 3 mpg..

VTJeep

The ECM, aka PCM aka ECU aka something else.. Is located on the right side firewall next to intake housing. It's got 3 harnesses. I had to replace mine recently and did it with a refurbished one from the net.. I can send a link if ya want..

If your messing with electrical components: use electronics cleaner and some dielectric grease to help improve conductivity and keep out crap.

ChilliXJ

Thats what my overhead says im doing...and my temp is 1/4???

ChilliXJ

Ok, so i now have a 195 stat installed. Jeep gets to operating temp now and doesnt overheat....heater blows nice and hot....upper radiator hose is hot ( obviously the stat is working) ....but my radiator cap is only warm (used to be hot and dribble if you took it off straight away) cap has been replaced too....is that normal?

VTJeep

glad to hear things are good with the jeep! and yes, replacing the cap is a good thing. the spring tends to wear out and cause them to become ineffective. sounds like its working normally.. idk about the cap only being warm, how long do you run it before checking heat? might need to run for a while at temp to make it hot..