Overheating uphill only

[joe_peters]

The thermostat should be Ok, but watch for it running too cold to make sure it isn't stuck open.

Glad its finally diagnosed, kind of like having a weight lifted off your back.

Good luck.

 

[CherokeeManatee]

So just an update for anybody interested:

I put in a nice 3 core csf radiator from DPG Offroad, new water pump from NAPA, and a new 16lb cap last week...threw in a new hose while I had the chance,too. The crack on my old radiator is almost non-existant and hard to find which is probably why it was so hard to diagnose.

Went wheeling at Kennedy Meadows this past weekend...3.5hr drive gaining elevation the whole time. It was in the 90*s the whole way up and through the Mojave...so the engine still got hot and only got near the 3/4 line (230*F?) once going up a long grade on the I-5.

The other cherokee I caravan-ed with got hotter than mine did and he just put in a rebuilt engine, stock cooling and stuff.

Throughout the drive I had the AC on low-mid. Temps stayed below 210* on flat and downhill runs. On the uphills the temps were manageable staying at or slightly above the 210* mark.

Wheeling was mild for the most part and the temps stayed at or slightly above the 210* mark on steep uphills with the AC on low-mid.

I'm very happy with the new radiator as it seems to have cooled the entire system 30*F across the board.

I'm guessing the reason the engine still got hot was because it was hot this weekend however I'm still curious to see if I can get the temps to never get hotter than 215*ish. Something had to have change because this was possible at one point in the jeep's life after the lift.

 

[joe_peters]

You can test the fan clutch to see if its doing its job:

From the 90 FSM:

"The cooling system must be in good condition prior to performing the test outlined below to ensure against excessively high coolant temperature.

CAUTION: Ensure that there is adequate fan blade clearance before drilling.
(1) Drill a 3.18 mm (1/8 in) diameter hole in the top center of the fan shroud.
(2) Insert a dial thermometer -18 degree to 105 degree C (0 degree to 220 degree F) with an 8 inch stem, or equivalent, through the hole in the shroud. Ensure that there is adequate clearance from the fan blades.
(3) Connect a tachometer and an engine ignition timing light (to be used as a strobe light).
(4) Block the air flow through the radiator by securing a sheet of plastic in front of the radiator (or air conditioning condenser). Use tape a the top to secure the plastic and ensure that the air flow is blocked.
(5) Ensure that the air conditioner, if equipped, is turned off.
WARNING: USE EXTREME CAUTION WHEN THE ENGINE IS OPERATING. DO NOT STAND IN DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE PULLEYS, BELTS, OR FAN. DO NOT WEAR LOOSE CLOTHING.
(6) Start the engine and operate at 2400 rpm with the timing light (strobe light) aimed at the fan blades. Within ten minutes the air temperature (indicated on the dial thermometer) should be 88 degrees C (190 degrees F). Satisfactory operation of the fan drive requires that it engage before or at 88 degree C (190 degree F). Engagement is distinguishable by a definite increase in the flow noise. The timing light will also indicate an increase in the speed of the fan.
(7) When the air temperature reaches 88 degrees C (190 degrees F) remove the plastic sheet. Satisfactory operation of the viscous fan requires the air temperature to drop 20 degrees F (11 degrees C) or more. A definite decrease of audible fan air flow noise should be noticed. Replace defective fan assemblies."

 

[carves]

X 2 ......... On time to check the fanclutch.

 

[CherokeeManatee]

Thanks for the instructions, I'll look into it and report back...eventually

 

[Bigredrage]

Hello all,

I figure this is a good place to piggyback vs making a new thread on a similar issue.

I have a 1994 XJ with around 110k miles on it. (33x12.5's, long arm terraflex 4.5 inch lift, 4:56 gears, work in progress)

I bought it around 94k miles and have done a considerable amount of wheeling in it already and broken/replaced tons of stuff. I have new springs coming in the mail now to bring my lift back up as it is sagging quite a bit. I also just replaced my transfercase due to my old one exploding on i-10 but on to why I am here today.

Prior to my xfercase explosion I went camping up on the mogollon rim. Heading up to payson I almost overheated a few times and finally did once when climbing the highest elevation spikes on the freeway. Whenever I am on stable ground or going downhill I have no issues (downhill obviously ram air helps). I would put to the top of the hill almost overheating and then it would drop back to normal once I got over the hill. I also tooled around payson and up on the rim plenty without issue, only uphills caused problems.

Since I can drive all around town without issue I figure that widdles the issue down quite a bit.

I have a 2 row radiator that I put in just a few years ago along with doing new hoses. The thermostat was replaced over a year ago.

Because I can drive all around town without issue, I figure it is NOT the thermostat. (I snapped a bolt in the head doping the thermostat in the past and want to mess with that housing as little as possible to not further cause problems) is that a reasonable assumption based on uphill issues only that the thermostat would not cause it? In my experience, bad thermostat means you overheat under any conditions, not just uphill.

The only part of the cooling system I have never messed with is the water pump so I ordered a new one and its in my garage, I plan to slap it on soon.

With a recent radiator, hoses, tstat I figure all that is left is the water pump that could be causing the issue (assuming no cracks in my block and etc)

My temp gauge has never been fully functional so it is extra important I run at low heat levels as when I start to get real hot its usually a surprise and I dont want to have those surprises. I have only overheated once so far and dont want to do it again. My miles are too low to wreck the engine already

As far as I know my regular fan works fine and my electric fan does kick on (not sure when right now but I know it does turn on and go)

Thanks.

 

[Bgbdbn]

I would put that water pump in. In all of my Jeeps (three XJs and one wrangler) it seems the water pump was the weak point in the cooling system. They all had the 4.0 six and on all of the the water pump fins were rusted off. Mine would start with intermittently getting a little hot then cool back down and drive normal for awhile. Then all of the sudden they all got hot and over heated.

 

[xjtrailrider]

You replaced the hoses? I thought I read that in there somewhere.

Don't let the parts guy tell you that your lower radiator hose doesn't need a spring on the inside.

You'll suck the hose shut at higher rpms. You usually don't notice it until the tranny kicks down to do things like passing or going up a hill.

I fought that for 6 months until someone told me the "springless" hoses don't work. I actually spent less money at Napa for the cheap one with the spring than I would have on the fancy one without a spring.

This! I just fault this issue on our 89 MJ with a 98 long block, it would overheat on long pulls here in the mountains. I had a Gates hose in there but old age made it weak. I put a new Gates in(no spring) and all is well. This was the first time this has happened to me on a XJ/MJ. I have never run a spring in the lower hose but the thicker Gates hose usually doesn't need one until its life expectancy is reached.