One thought. Go to Napa and get a 703-1396 cap for the reservoir.

 

Cool. I will try that first. Thanks!

 

My gravel road climbs 1,500 feet in three miles to get home. Steep and windey with washboard means very little air flow. I depend on the E fan and the fan shroud, or it will boil when I park it. Of course it would go on to overheat, but I'm just 10 minutes up.

The fan should come on when you turn on the defroster. It's relay is alone on the LEFT inner fender. It's switch is on the radiator there near the battery. (218*) Sort of tough to test that switch! If it's boiling and the fan is not on with 50/50, even at ambient pressure I think the fan should be on.

Yea, I had left my cap a tad loose just a couple of weeks ago and it made a scene. You can always squeeze a hose and see if it's hard.

 

Interesting. I had it on heat the whole time, not defrost. I will try that out. The relay, you mean right as in drivers side when looking at motor? Or the other right, as in sitting? I'll find it I am sure.

I've taken this jeep on dozens of trips in the mountains, up gnarly stuff and easy stuff, snow and dry both. In the past it never over-heated or even really attempted to. Since I got that after market bottle I've had nothing but issues. The warped head and blown gasket didn't help either lol.

I do some work on boilers at work, and one thing that makes them run either really well or really bad is the flow rate in them. Too fast and you don't pick up enough heat from the boiler, too slow and you don't remove enough. I wonder if there is a way to tell in a car, like some sort of delta T test. In a boiler you look for a steady drop across the inlet and outet (the delta T) and you want to maintain something like 30degrees. In a car, well, it might be worth a shot, maybe the water pump is not putting the flow out it needs.

I'll try my local napa tomorrow for that cap and check if the fan comes on with the defrost.

Thanks for yet more ideas.

EDIT: where I am at, its not unheard of to go from around 3000 to 7000 feet or more. Granted it happens over some miles, but I should have thought I would have seen this issue in years prior ...

 

Here's the relays on the right inner fender.

The fan relay is on the left inner fender and sits by itself near the fuel pump ballast resistor.

 

OOPS..I do that allot and make an effort to double check. (I was dropped on my left/right side at birth) . Left, drivers side, alone there on the inner fender!

Yea, see that it comes on on defrost setting. Also I think you can unplug the two wire temp switch rite there by the battery and jump the Jeep side together to see that it's all working. (except the temp switch of course)

 

@cruiser54

You were right, that napa cap did the trick. Thanks a mint for that tip!

As for the performance now that I've run it a good number of times over the last month - fuel mileage is down in city but seems the same on highway. Getting about 400 miles on a full tank of premium. Getting a little over half that in town, but thats a lot of stop lights/signs etc. Used to be better but memory doesn't work well enough to say by how much lol.

After I got that cap cruiser54 mentioned, I noticed a difference right away. The cap bites the threads much better but what I really noticed is that it seemed to seal on the gasket much better than the one that came with the tank (or the common OEM replacement). I was using some of that blue gorilla strength teflon to give some bite to the other cap but never could get enough to really seat the top seal I guess. This new cap bites well and makes that seal, which makes all the difference.

I notice as well the transmission is not as smooth in shifting as it used to be. Its not excessive in rpm rate changing on shift, but has more jolt to it now. I can only assume that when I repositioned the sensor to make it idle correctly it affected the transmission as it appears to be a combo sensor (from what I gather anyway). Not going to worry about that as its running great really.

I do think I could benefit from a lower threshold on the sensor for the electric fan. It does come on, but its got to be pretty hot to do so. So either I find one that is lower or permanently put a manual switch on it. I temp rigged one up and drove around town (it gets the hottest at low speeds and idling a lot). The electric fan keeps it at a good temp, it just doesn't come on soon enough.

Also happy to report that I haven't broken down after the head job. I was worried that the higher compression with the valve job would affect my rings which have 188k on them. But so far so good, no problems.

Also very happy I did all this work as we had storm come through yesterday in which the morning temps were 35 and rain and by early afternoon temps were 20 deg f and very nasty roads. The old jeep with a good set of studded tires once again showed itself to be a true performer.

Thanks for all the input, I learned a lot from this place and the kind people who share what they know!

 

I put one of these on my previous 88 that kept boiling over, even after a head job. Tried a new factory bottle and cap and it still boiled over. Finally I got this;
http://www.summitracing.com/parts/mor-63655/overview/
No more problems after that.

 

Trans isn't THAT sensitive to the TPS adjustment like the "engine" side is.

How old is the fluid and what's it look like?

 

Umm, age I am not sure. I don't put a lot of miles on this, so maybe 5 years now. I am not even sure I've added any to it in that time. It has rarely needed any since I've owned it (98). I check it but thats about the extent of my involvment with the tranny.

Color wise, its not gotten that dull look yet. Not as clear and bright looking as it is out of the can of course but you know what I mean, not looking like it breaking down.

I think I've put on about 900 miles since I did the work on it this fall. Thats about half of what it will get an entire year typically, often even less. Its a hunting and bad weather backup rig now

 

Try this:

https://www.cherokeeforum.com/f2/free-quick-fix-41821/