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Overheating, Cooling Fan question.

navistarman1980

NAXJA Forum User
Location
Calhoun, TN
Hello there!

I'm very new to Xj's as I just bought my 1990 a few days ago. Its been running hot at idle, and sometimes while driving through the mountains. The temp is always changing.. it goes from 180-210 within a matter of seconds. If I let it idle for a long period of time... the resivor starts to overflow, and I shut the engine off. Another thing I noticed is that the electric fan only comes on when the A/C compressor is on. Is the electric fan supposed to assist the mechanical fan???? If so where is the temp switch for the electric fan? I have replaced the water-pump and t-stat (192degree) and shes still running hot!!
Any thoughts?

Thanks,
Justin
 
Welcome to NAXJA.Your cooling system probably has an air pocket that needs to be "burped " out.
The radiator has probably filled up with enough crud to render the temp switch for the aux fan inoperative-its located in the tank on the drivers side IIRC.The fan is to come on with the AC.
The best thermostat is the factory one with the air bleed hole,which is installed at 12 0clock to bleed trapped air out of the system.
Also check the condition of the cap on the pressure bottle-these are known to leak and let the engine over-heat.
Also use the "Search" feature--there are hundreds of posts on this problem

Wayne
 
if you don't have the weep hole in the thermostat flange you will get air trapped in there. on a new one the temp sensor is in the top of the tstat housing, with the air trapped up there you get false readings.
Rule of thumb, low speed and traffic heating is usually the fan clutch. They do go.
 
if you don't have the weep hole in the thermostat flange you will get air trapped in there. on a new one the temp sensor is in the top of the tstat housing, with the air trapped up there you get false readings.
Rule of thumb, low speed and traffic heating is usually the fan clutch. They do go.

Overheating at low speed/idle can also be caused by the elec. fan not engaging at all.

On a 90 (closed system) RENIX the switch location is as stated by Wayne. The electric fan should come on at appx. 215*F to 225*F (it varies). If it isn't coming on there's a problem with the switch/sensor.

Burping is tedious but getting the air out is important. Like RichP says the weep hole should eliminate the air after a while. You can either buy a t-stat with weep hole (92 & up) or drill two small holes (1/16") in the t-stat flange, the actual t-stat, not the housing (one on top, one on bottom). That should allow enough air to move through the system and eventually burp out and then become self-burping.

...and X2 on the fan clutch going out. That was my problem after chasing other possibilities for a couple weeks. My old one was shot.
 
Overheating at low speed/idle can also be caused by the elec. fan not engaging at all.

On a 90 (closed system) RENIX the switch location is as stated by Wayne. The electric fan should come on at appx. 215*F to 225*F (it varies). If it isn't coming on there's a problem with the switch/sensor.

Burping is tedious but getting the air out is important. Like RichP says the weep hole should eliminate the air after a while. You can either buy a t-stat with weep hole (92 & up) or drill two small holes (1/16") in the t-stat flange, the actual t-stat, not the housing (one on top, one on bottom). That should allow enough air to move through the system and eventually burp out and then become self-burping.

...and X2 on the fan clutch going out. That was my problem after chasing other possibilities for a couple weeks. My old one was shot.

Hi,
And thanks for the great information..
But shouldnt that electric fan be kicking on before 210*F? The resivor starts boiling over at around 210*F which makes me nervous.
 
the fan should come on around 220, and with the A/C and defrost settings. it can be wired to a switch if you want control of it. if its boiling over around 210 i would replace the temp sender which is on the drivers side of the back of the cylinder head. i would also replace the coolant bottle. sounds like at least one is bad. if you end up having to replace the whole cooling system, i would convert it to the open style like 91+ XJ's. just do a search on here. its been done a million times.
 
the fan should come on around 220, and with the A/C and defrost settings. it can be wired to a switch if you want control of it. if its boiling over around 210 i would replace the temp sender which is on the drivers side of the back of the cylinder head. i would also replace the coolant bottle. sounds like at least one is bad. if you end up having to replace the whole cooling system, i would convert it to the open style like 91+ XJ's. just do a search on here. its been done a million times.

...and then there's that. If the coolant bottle or cap is compromised (cracked etc.) it'll start to "boil over" when it's pressurized because the hot coolant is finding the path of least resistance(boiling temp of straight water is 212*F at sea level, so really it's gurgling out at 210 and just appears to be "boiling").

If you opt to try the things mentioned instead of the full conversion (there are still problems with the closed system as well) I'd go with 1.) replace the bottle AND cap (about $40 at the DEALER) 2.) drill the t-stat flange and make sure you have a 195* t-stat ($10 for a new t-stat) 3.) Test the temp switch on the radiator and/or wire in a switch for the e-fan and finally 4.) test/replace fan clutch ($45)

If you do the whole closed system conversion you'll still have to do 2,3 and 4 and it will cost about $250.00 :bawl: for a radiator, hoses, heater control valve and the fan clutch.
 
...and then there's that. If the coolant bottle or cap is compromised (cracked etc.) it'll start to "boil over" when it's pressurized because the hot coolant is finding the path of least resistance(boiling temp of straight water is 212*F at sea level, so really it's gurgling out at 210 and just appears to be "boiling").


which is why i said at least one is bad.
 
Like others are saying, make sure the thing is "burped". The trick on my '88 has been to park with the nose pointing downshill, loosen the temp sensor on the drivers side towards the firewall on the head, fill until no air comes out (only antifreeze!). Tighten the sensor down, run up to temp with the cap off the reservoir, refill when it cools down to right level, keeping it from sucking air.

The weep hole in the t-stat is important -if you don't have one, drill a small one. Make sure its at 12-o-clock.

Very likely the bottle and or cap (or both) are cracked or not sealing anymore if its been run to the point of overflowing a few times. I've also gotten bottles and caps at Napa and O'Reilly's, only the O'reilly one worked. The Napa bottle always leaked. One of the few parts I've been disappointed in there.

Oh- the fan on mine generally turns on somewhere well above the 210 mark on the dash guage - likey 220ish. So long as the system is burped and seals tight, it works fine. Hot, yes, but fine!

THese can be a pain the arse to figure out the first time, but once you know the drill, it isn't as bad as it sounds.
 
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