Overheating question

[banshee]

Here’s my question

I bought an XJ 4.0L HO for parts, it runs well but hot 220+, as it runs and the temp climbs the water is blown into the overflow bottle and then it overflows in about 15-20minuts, 16lbs cap seems to me to well over that pressure ‘unable to confirm’ after shutdown with relieve lifted to took several minutes to relieve the pressure, upon compression test everything looks normal ‘not good’ but normal for the mileage, 200,000+

Test

Fan belt off, motor running, top hose removed at thermostat housing I can see small bubbles ‘Not constant’ , but no water blowing out the exhaust pipe? Suspected head gasket, one more point it doesn’t miss??? better ideas???

 

The good news I didn't pay a lot for it, but the body or what's left of it, I’m not sure i could get my money back even for junk.. :doh: B…

[philbert001]

Mine is a renix/closed system, but if you think about it, it was doing the same thing. I had overheating problems, so I swapped in a 180 t-stat. Still overheated. My electric fan wasn't kicking on till 230, and by then, it was too late, so I hardwired the relay to the ignition switch. Problem solved for the next few years. It would occasionally, on a hot day, blow some coolant out of the bottle, (which is where the pressure cap is on the closed system), but that didn't concern me much because it wasn't overheating.

Then, this spring, I decided to take this driveline out of my XJ, and put it in my MJ, and when I did, I realized how rotten my factory radiator was, so I ordered a new one. After installing it, not only did she run cooler, (180 on the dot with no fluctuation at all), But she picked up 10 lbs of oil pressure, and my volt gauge, which has registered 13 volts, since the day I bought her, started charging at the desired 14 volts!

I was baffled to be honest, but the only thing I could think of, is that The radiator was so plugged up with crap, that the water pump had to build up lots of pressure to flow water through the plugged up radiator, and That was why it was puking coolant from the pressure cap. I'm also assuming that my gains in oil pressure, and charging voltage were a result of the decreased load on the engine due to the water pump no longer having to build up 15 lbs of pressure just to flow water.

Hope you get her sorted out. Maybe this helped, maybe not, but maybe it gave you more to look at. Take the grille out of your truck and fire it up. Let it get up to temp, and feel the radiator for temperature consistency. I believe it should be hottest at the upper hose corner, and coolest at the lower hose corner, and a gradual temp change from one corner to the other. If you have extreme differences, (Like super hot spots right above or below cool spots), then I'd say you have a plugged up radiator too!

[Fezzik]

wow, I was just about to post up a very similar question, I was going to try a flush to make sure it wasn't bad coolant I had, but I think I'll just have them replace the radiator too, good pm since my truck was sitting for ~4 years before I got it back on the road

[Grant]

I'm having a bit of a time with my 2.5L. I just replaced the motor since we lost the origional one to a blown head gasket. anyway, New hoses. new radiator, new fan belts. new fan clutch. still overheats. It's only 85 deg here. I'm also confused as to where the sending unit is for my guage. is it the little brass button sender with the brown wire on the back left end of the head?

[mvusse]

I'm having a bit of a time with my 2.5L. I just replaced the motor since we lost the origional one to a blown head gasket. anyway, New hoses. new radiator, new fan belts. new fan clutch. still overheats. It's only 85 deg here. I'm also confused as to where the sending unit is for my guage. is it the little brass button sender with the brown wire on the back left end of the head?

 

It is in the driver side back corner (near firewall) of the head, single wire coming off it (don't remember what color).

 

How are you diagnosing overheat? Gauge shows hotter than you like? Coolant boiling? If the latter, does the system hold the correct pressure?

 

Anything up to 245 degrees is within operating specs. Properly working system should not boil until at least 265 degrees.

[Grant]

Well I've never been sold on the accuracy of my guages as my tack reads 2k at idle lol

I'm looking at the right sending unit then. Oh, a new 13lb lever type rad cap as well. I'm going to borrow an infrared thermometer tomorrow to see what I get for a reading at the thermostat housing and the sender. I'm just hopeing int not the waterpump.

[mvusse]

Well I've never been sold on the accuracy of my guages as my tack reads 2k at idle lol

I'm looking at the right sending unit then. Oh, a new 13lb lever type rad cap as well. I'm going to borrow an infrared thermometer tomorrow to see what I get for a reading at the thermostat housing and the sender. I'm just hopeing int not the waterpump.

 

13 pound radiator cap will work, but it's supposed to have a 16 pound one.

[2360]

I had overheating problems a few times in past years.

 

The solution for me was a new/used rad.

[Grant]

When I put the motor together I had the head done and all new gaskets, it pressure tested good. The rad is new as is the cap a 14lb lever release. All hoses are new as well. They only issues I can figure is maybe the waterpump or, the heater fuse was melted but not blown so I have it out at the moment. I was suprised to see the w/p is only 25 bucks and no core. I'm debating swapping the waterpump. It is the last old peice of the entire cooling system except the block and head!

[Grant]

I think I know what it is... my new block is from an 89. It had a serpentine belt. my 86 has conventional belts. I'll bet the waterpump is wrong for my belt setup. I think that serp w/p run backwards from the regular belts.

[maddzz1]

I think I know what it is... my new block is from an 89. It had a serpentine belt. my 86 has conventional belts. I'll bet the waterpump is wrong for my belt setup. I think that serp w/p run backwards from the regular belts.

 

 

Yes, I'm pretty sure the 89 is a reverse flow water pump.

[Grant]

there is a difference between the v belt setup and the serpentine. The vbelt waterpump fixed my cooling. it all good now.

my biggest probles is that the clutch is like somebody is stepping on the peddle constantly. if I push it in, it goes so far that I get the clicking sounds. the clutch/pp/and bearing are all new. my slave is external on the bell housing. it eas not touched inthe engine swap. the new clutch disk was only an 1/8th thicker than the one I took out. what could cause this? no mater what I do the clutch will not engage.