XJ overheating and blowing cold...

[dubbleJs]

So this first happened last week... I had been driving around for a while, shut my XJ off then when I started it again it overheated and was blowing cold air through the vents. Of course it was -20 out, so I sat there pondering a thermostat swap in the Crappytire parking lot. After shutting it off and starting it up a few times running around to different stores in the south for parts and tools...it started running fine again...good temp and blowing heat.

So I came home and put a new Tstat in it anyways. This was on thursday.

Now this morning I start it up, and about 6 blocks from home my engine temp climbs quickly towards 100+...which is impossible in -20 if it was running right. Sure enough, no heat blowing vents and a motor on its way to overheating.

What do you guys think, waterpump? Maybe another stuck/bad thermostat?

I don't smell coolant through the vents so I dont think its the heater core.

[Pookapotamus]

sounds like your coolant is not rated for -20 if you have a testor check it.

[Spinalguy]

sounds like a head gasket. Was the coolant level still full?

[JENSSEN]

Frozen Rad,.. as noted above I bet your coolant is weak and freezing up, you may want to check your water pump too as when the systems freeze up it usually pushes the bearing out ,..

Had it happen once or twice

[Marco]

i remember swapping my heater core hoses one time to flush it backwards in case there was junk somehow. just a thought. But those guys are right about the coolant % also

[JackstandJohnny]

so do yo suggest a 50/50 mix?

[cLAY]

X2 on the weak anitfreeze and yes a 50/50 mixture is best. If you cann't drain it all try to get about 2-4 liters out and top it back up with straight antifreeze.

To get 50/50 I buy two jugs and dump all of one in, then I fill the empty jug with water and pour that into the rad, now you've got 4 liters of A/F and 4 liters  of water in your motor. Next pour half of the 2nd jug of A/F into the first jug and top up both jugs with water. You now have two jugs of premixed A/F(50/50). Use those to finish topping up and you'll probably still have part of a jug left over for next time.

[hps4evr]

my first thought would be the t/stat. and you changed that, did you run all the air out of the cooling system after? that would be my next thing to check. you can back flush the heater core to help with heat, but when they get plugged they dont usually cause an overheating issue.

[dubbleJs]

Thanks for the replies guys. I think you hit the nail on the head with the bad coolant mixture. Just got home and pulled the heep in the garage, the lower rad hose is frozen solid and my rad has ice in the top of it...Gonna let it thaw out for a while.

As I was driving it around back to the garage it stalled, I fought it to start back up and it was running like crap, but not overheating yet. Not sure what other problem is arising now...

[Vexta]

You now have two jugs of premixed A/F(50/50). Use those to finish topping up and you'll probably still have part of a jug left over for next time.

So simple... and yet I've never though of doing it this way.  Keeping this in mind for next time.

[dubbleJs]

So I got it all fixed. Thawed it out and drained all the coolant, then refilled it. And theeeeeeen it started leaking......my rad cracked right at the neck for the drain plug. 

New rad is in now though, and the motor is running a bit cooler than it ever has! (To look at it on the positive side...)

X2 on the weak anitfreeze and yes a 50/50 mixture is best. If you cann't drain it all try to get about 2-4 liters out and top it back up with straight antifreeze.

To get 50/50 I buy two jugs and dump all of one in, then I fill the empty jug with water and pour that into the rad, now you've got 4 liters of A/F and 4 liters  of water in your motor. Next pour half of the 2nd jug of A/F into the first jug and top up both jugs with water. You now have two jugs of premixed A/F(50/50). Use those to finish topping up and you'll probably still have part of a jug left over for next time.

I was actually just talking to a buddy about this the other day, he did it a while ago in his car and it caused him problems. The water and coolant didnt mix properly by the time he parked it, then the water froze and did the rad in..... Just something to think about.

[cLAY]

Did he dump ALL of the antifreeze in and then all of the water?  I could see it freezing in the rad that way. To be honest I've never tried it where I've left it out below zero after filling it. I've always ran it through a few cycles where it heated up and cooled down before having to leave it outside. Having a heated garage has its perks....

[Zombie]

any time I have filled the rad, I always just go strait to the 50/50 mix, find an empty distilled water jug and fix it up and add it that way, figured it was sasier that way.

too bad it cracked the rad.
I thinkI have a cracked overflow tank of bad hose somewhere, have to hit pnp

[dubbleJs]

Did he dump ALL of the antifreeze in and then all of the water?  I could see it freezing in the rad that way. To be honest I've never tried it where I've left it out below zero after filling it. I've always ran it through a few cycles where it heated up and cooled down before having to leave it outside. Having a heated garage has its perks....

I am not sure exactly what he did, something like a jug of coolant then a jug of water. He probably just got unlucky and didnt let it run long enough to cycle and mix... a problem easily avoided by pre-mixing though.

[Tinkerer]

I'm glad you found your problem. Too bad it cracked your rad, though in typical Jeep style, it was an "upgrade"!

At the very least, the vehicle has to run until a few minutes after the thermostat opens up... and have the heater on hot so that water circulates through the heater core as well.  It can seem like a long wait.

A day or so after I read this, mine froze up (cold Tuesday). I figure when I had a leak I was working on, what I thought was my 50/50 was on the weak side, so I was good for -20 and perhaps a bit lower, but -29 did it in. Luckily a lot of start/stop/wait cycles allowed it to thaw and I headed down and bought antifreeze and began adding pure antifreeze until the system was full again. Now I have to measure it to find out what mix I really have now.