captainofiron

Well a few weeks back it snowed like 7in, I was driving to work, and BANG, it started overheating.

So I limped home and parked the old XJ.

The next weekend, I popped the hood, and started her up, well the waterpump was squeeling like crazy.

So I then noticed a burst hose. So I replaced the hose, the t-stat, and the waterpump.

The other day I ran it with all the new stuff, and it was getting over 210 easy and climbing, and I noticed that the aux fan wasnt turning on.

So I drove her around, and it was still wanting to overheat, so I cranked on the heater fullblast and it was getting to right around the 3/4 mark on the temp gauge, and staying just slightly below the 3/4 mark.

and if I turned off the heater it was climbing to 3/4 and looked like it was going to go over again.

What do you guys think?

I hooked up the fan directly to the battery and its going strong.

I swapped the relay for teh a/c and the fan and still nothing, checked the 20A fuse for the fan, and still nothing.

Anybody have any ideas what the problem might be?

I was thinking to run a wire to the fan direct from the ignition voltage source on the fuse box and seeing if it overheats.

thanks for the help in advance guys

COSXJFAN

How many miles are on the rad? It could be plugged...you could also have a bubble in the system.

djb383

If there's good coolant flow thru the block, head and radiator you shouldn't need any fan(s) while driving around......especially this time of year with the heater on. If the flow of coolant is restricted thru any one or more of those three areas then overheating is likely. As already suggested, me thinks the rad is the problem. Don't know about a '91 but the book says electric fan on at 218F and off at 209F, no a/c for a '98 XJ.

captainofiron

Its about a year old, my old one cracked, when I caught about 5ft of air in a drainage ditch


that is what I was thinking too, but the fan isnt turning on at all,

I am gonna try to burp the system this weekend, and replace the sensor on the t-stat housing and see if that solves the fan issue.

I am starting to think it might be the new t-stat not fully opening or an airbubble

is there any way to check the sensor, like do you guys know the ohms I should be reading? both hot or cold?

captainofiron

Oh I forgot to add, when I replaced the cracked radiator, I also flushed the coolant system with a prestone kit

Nobody else has any ideas about the extra fan?

87m6chris

I was in the same boat only I had replaced absolutely everything in the cooling system with new parts but still the gauge was hovering around 230-235* even with AUX fan on full. So I dropped in a 180* thermostat instead of the 195* that solved it. Now it sits steady on 205-210. But now I'm afraid the ECU is running in open loop because of the cooler temp up at the front where the ECU sensor is and my gas mileage is going to suffer because of the rich condition. This is by far the worst designed cooling system I have ever seen.

captainofiron

well I worked on it last night, I saw some weird readings from the coolant sensor that is in there, it showed it had continuity and then none, and the resistance was all over the place. I jumped the coolant temp sensor in order to see if thats why the fan wasnt working, so guess what, the fan turns on and runs like a champ, so I drive down to the local AZ and picked up the new coolant sensor.

But its still overheating. It gets up to about 3/4 without the heater on, then I turn on the heater and it goes down to a little over 1/2. if I drive with the heater on its fine, it just stays inbetween the 1/2 and 3/4 mark. So I am guessing its needing to be burped, or I hope.

Other things I am thinking might have gone bad, the fan clutch, which I replaced last year, and the brand new t-stat that I slapped in there earlier this week.

RevZeroX

maybe pop the t stat out and put it in a pot a boil water to see if it open, also what oil look like? when it warms up check top hose to see if it has flow to check for blockage. coolant system pressure test maybe? just ideas.

posjeepxj

Just convert it to run on alcohol and dont run a radiator

captainofiron

I am gonna do that tomorrow, I was going to work on it tonight, but I didnt get a chance, Im gonna try to burp it first, then if it still doesnt work Im gonna see what happens

The oil looks good, I do need to replace it though, the coolant was clear and green, from the last time I replaced it.

I was drinking... oh wait. haha

captainofiron

ok so I replaced the coolant temp switch (the one for the fan on the tstat housing), and I burped the system, well I think I did, I really couldnt jack it up high enough to get the radiator cap high enough like I had wanted. BUT still my aux fan isnt working.

SO, I am starting to think this, that Autozone sold me a faulty thermostat, OR the temp sender for my gauge is off, AND/OR the connector to my fan is screwed up.

Anyways, I turned it on and let it idle till it got hot, and it got to the 3/4 and stayed there, it wouldnt go higher or lower, then I turned on the heater and it dropped to just above the half mark.

Here is a picture


Anybody got any ideas?

87m6chris

I think you should try the 180*F Tstat. I tested 6 thermostats from 3 different suppliers,
Napa, Chrysler and Stant, 2 from each. All of them stamped 195*F, all them opened at 205 - 210*F. So brought home a 180*F Tstat and it opened exactly at 180*
What are you going do? (and my thermometer is very accurate)
Your Aux fan is a good back up but the Rad. should do the job 90% of the time.
I assume your 91 xj is what this thread is about so your either running renix or OBD1
neither of which will be affected by a 180* Tstat.

posjeepxj

time for an ls1 swap

truckntractorhick

do the boilin water test!

captainofiron