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Still Overheating-New Engine and Cooling System

Basic Facts: 89 Cherokee with a rebuilt engine (long block from reputable local shop). Just got through putting it in, runs fine. Also put in all new cooling system including new radiator, thermo fan clutch, turtle, thermostat (with proper bleed hole), new hoses, etc.

SUCKER IS STILL OVERHEATING

We've checked timing-its spot on. We've burped this SOB so many times, you'd think we were parents. Any idea what else to check?

Here's how we've been burping:

1. Fill system till it won't take any more through the turtle.
2. Pop upper rdiator hose and fill till it comes out of thermostat housing. Top off hose (hand over thermostat), put in place and tighten clamp.
3. Point downhill and pull temp. sensor from rear of head to release air.
4. Start and warm up with cap off.
5. Install cap, let come to pressure.
6. When it gets hot, shut her down and wait to cool. Relieve pressure at cap on the way down.
7. Try again.

Have we been burping wrong? Any help at this point truly appreciated since were running out of options (there ain't much left to replace).

No obvious leaks.
 
what temp is the gauge showing?
could be a bad sender/false reading? unless the coolant is boiling over.
if you could get a thermometer in the coolant and get another reading just to check your sender and gauge.

fwiw, when I refilled my coolant I poured some in the bottle and started the engine and kept adding till it filled. didn't put the cap on till it got full.
 
are you getting circulation? some radiators have little plastic covers that are inside the hole and can be missed. Just giving some input. But I agree with Grundan and try another sensor. But deffenatly check for flow.
 
grundan said:
what temp is the gauge showing?
could be a bad sender/false reading? unless the coolant is boiling over.
if you could get a thermometer in the coolant and get another reading just to check your sender and gauge.

X 2
I had what sounds like the same problem with my 91.
After spending $300.00 to fix it and still had the same problem, I went to Wal-Mart and bought a meat thermometer and checked the temp.
208 deg.
Bought a new gauge, fixed the problem.
Heres how I installed the sender.....
(would not fit the hole in the back of the head)
100_1585A.jpg
 
Update: Just got back from the radiator shop and others were correct about the sender. It appears to be giving false readings.

We still have a problem with pressure building in the system (yes, it blows like a gyser).

Were beginning to suspect blown or mis-installed head gasket, although were getting solid readings of 140 PSI accross all cylinders during a cool compression test (dry).

I guess the next step is to take it to a shop for a snif test to see if we have exhaust in the water.

Any other thoughts?
 
I don't know if you've already checked this but i had the same problem and it turned out to be the new waterpump we installed. The impeller fell right off inside the block. I went through alot of testing and overheating until i found this.
I am not sure this would apply because of your new engine install or not but just a FYI.
 
walkeddownalameda said:
I don't know if you've already checked this but i had the same problem and it turned out to be the new waterpump we installed. The impeller fell right off inside the block. I went through alot of testing and overheating until i found this.
I am not sure this would apply because of your new engine install or not but just a FYI.

Hmmmmm... possible, but not likely. I'll hold that out should sniffer test indicate head is good.

Any other ideas out there?
 
Have you replaced the pressure cap? Mine gave me fits trying to figure out what was going on after I replaced the water pump, bottle and cap. I could start the engine, and watch the coolant level rise until it overflowed. I squeezed the upper hose and noticed there was no pressure building. Ended up getting a defective cap from the dealer so I put the old cap on and no geyser/overheating.
 
I have only hade my 87 xj for a few months now and am not greatly familiar with the closed cooling system. With that said, is there any chance you got the smaller heater hoses hooked up wrong. The ones that go to the heater valve. I would look at that diagram just for giggles.
 
MJmk said:
Have you replaced the pressure cap?

Several times. Got a bad one with a new Quadratek bottle (wouldn't open under pressure and blew up the bottle). Runninfg with good pressure cap now (or so it seems).

ChuckD said:
How is your CAT and Exhaust?

Seems to be good.... didn't have overheating problem till we replaced the engine. I don't think that's it, otherwise I should notice idling or other performance problems. Seems to be breathing fine.

Could a bad O2 sensor cause this? Its about the only thing we haven't replaced or tested.
 
positive that it's the proper waterpump? I read about the 258 pump being a proper fit, but the impellers were the wrong way. I wish I could find that thread, it had pictures. Just tossing out a possibility
 
87manche said:
positive that it's the proper waterpump? I read about the 258 pump being a proper fit, but the impellers were the wrong way. I wish I could find that thread, it had pictures. Just tossing out a possibility

Went through that already. Check, double check.

Any possibility the shop could have put the head gasket on wrong?
 
Is the water pump impeller spinning the right direction? Due to belt routing differences the pumps for XJ's, ZJ's, and WJ's look the same on the outside, but the impellers turn different directions.
 
drifto77 said:
X 2
I had what sounds like the same problem with my 91.
After spending $300.00 to fix it and still had the same problem, I went to Wal-Mart and bought a meat thermometer and checked the temp.
208 deg.
Bought a new gauge, fixed the problem.
Heres how I installed the sender.....
(would not fit the hole in the back of the head)
100_1585A.jpg

is the meat thermo in the coolant bottle a 'kosher' way of testing the heat in the system? cause i tried it but didn't know whether to trust it or not.

my 89 mj temp gauge reads about 240-250 when heated up, but a thermometer in the bottle read 185 up to bout 205 then itd knock back down and eventually start climbing again (indicating my thermostat is opening and closing properly)

im sure it isnt helping anything that i have a 97 block and header with all 89 everything else (closed cooling system)
 
$#!7
so it really could be running at 240
is there any other way to easily test it?
-nick

edit: additional info.
the 97 didnt have the temp sensor at the back of the block like the 89 would have so the previous owner modified the 89 temp sensor to be in the thermostat housing. (im not sure if the sensor is actually a 89 unit or a 97 unit) would this cause it to read wrong?
 
go to the parts store, buy a mechanical guage, thread that into the coolant temp sensor hole. Most of them come with a variety of adapters. I believe the CTS hole is 3/8" NPT
SHould cost you about $20.
 
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