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-   -   2.5 YJ overheating (http://www.jeepforum.com/forum/f12/2-5-yj-overheating-499777/)

--chris-- 12-26-2007 02:36 PM

2.5 YJ overheating
 
Hey guys, had a great time working on the heep for about 6 hours only to achieve nothing (other than stopping a small leak).

Heres the story, my 2.5 is overheating. So i remove the thermostat, the overheating stops...but now i have no heat. I go and buy a new thermostat from Advanced Auto. Drop the new one in, and it still over heats. Get another new one from the same place, this time different brand...still over heats. I double checked the installation with the haynes manual and i am certain i am doing that part right (spring side in the block right?) What the hell could be causing this? 3 thermostats in a row can't be defective, what else would cause the thermostat not to open other than the thermostat itself?

Yes, the top hose is cold while the bottom hose is hot...nothing is flowing through the top rad hose.

VT2BAD4U 12-26-2007 03:35 PM

Purge the system of air when you refilled it.?
Plugged radiator?
Bad waterpump?
Collapsed radiator hose? (internally)
Head gasket failure?
Those are the first quick things that come to mind.

ctm 12-26-2007 04:19 PM

define 'overheating' please

--chris-- 12-26-2007 04:46 PM

Quote:

Originally Posted by VT2BAD4U
Purge the system of air when you refilled it.?
Plugged radiator?
Bad waterpump?
Collapsed radiator hose? (internally)
Head gasket failure?
Those are the first quick things that come to mind.

Rad not plugged, the waterpump works, dont have a collapsed hose, or a failed head gasket. If i remove the thermostat, everything returns to normal except my jeep takes forever to heat up.


Overheating according to the gauge in the dash, it will slowly go up to the RED/260 mark on the gauge. When its overheating, i don't have any heat and the top rad hose is cold. This is why i think its the thermostat. But like i said, i replaced the thermostat....a couple times.

litel dart 12-26-2007 05:04 PM

try tacking off you top house to check if there is any thing blocking it onley reason i can see the top house wood be coled other than a broken water pum

--chris-- 12-26-2007 05:15 PM

Thanks, but i know the top hose is clear. It flows great when the thermostat is out, but once i put it back in it does not flow at all.

MEBDRB 12-26-2007 05:41 PM

IMO.....you have an air lock in the system. I have never owned a Jeep (yet) but it can happen on all cars.

Their will be people that can help you specifically on a Jeep, but normally I will fill the cavity that the t-stat sits in when changing to try and help eliminate this.

--chris-- 12-26-2007 05:44 PM

Quote:

Originally Posted by MEBDRB
IMO.....you have an air lock in the system. I have never owned a Jeep (yet) but it can happen on all cars.

Their will be people that can help you specifically on a Jeep, but normally I will fill the cavity that the t-stat sits in when changing to try and help eliminate this.

I'll pop the upper hose off tomorrow and see if this takes care of it with the t-stat installed.

Wouldn't this be a problem though, even without the t-stat installed like it is now. Because as it sits now, its fine...i just don't have heat because i have no t-stat.

ctm 12-26-2007 05:49 PM

check your thermostat(s) by putting in a pan of water on the stove and bring it to a boil. a good thermostat will open just before boiling.

MEBDRB 12-26-2007 05:53 PM

Good point.....but remember the t-stat has to have fluid on it at temp to open, it is possible you are just having bad luck and each time you put the t-stat in it locks because of not having fluid against the stat.

As I said, I have never worked on a Jeep yet, but lots of other cars, so hopefully a Jeep guy will come on and tell you what you need for SURE.

pat8942 12-26-2007 08:17 PM

IMO the best way to purge air is (On a cold engine) to take the heater hose off where it goes to the stat housing.
Pour coolant into the radiator until coolant comes out the stat housing fitting.
This assures you that tne engine block and radiator are full and free of air.
Reattach hose top off radiator replace cap fill overflow bottle to cold fill mark.
Start it up and run it at about 1500 RPM until you see the temp gauge hit around 190 and then drop a little.
If it does than you're in business.

Quote:

Originally Posted by MEBDRB
Good point.....but remember the t-stat has to have fluid on it at temp to open, it is possible you are just having bad luck and each time you put the t-stat in it locks because of not having fluid against the stat.

As I said, I have never worked on a Jeep yet, but lots of other cars, so hopefully a Jeep guy will come on and tell you what you need for SURE.


--chris-- 12-27-2007 08:19 AM

Quote:

Originally Posted by pat8942
IMO the best way to purge air is (On a cold engine) to take the heater hose off where it goes to the stat housing.
Pour coolant into the radiator until coolant comes out the stat housing fitting.
This assures you that tne engine block and radiator are full and free of air.
Reattach hose top off radiator replace cap fill overflow bottle to cold fill mark.
Start it up and run it at about 1500 RPM until you see the temp gauge hit around 190 and then drop a little.
If it does than you're in business.

okay, I installed a new t-stat again this morning and followed the above steps and it still won't open up. I thought that was going to take care of it, but i am still stuck with either overheating or no t-stat.i

Gasturbine 12-27-2007 11:57 AM

Never mind...I was vertically dyslectic this morning.

--chris-- 12-27-2007 01:48 PM

Any body have any ideas?

If it was not the winter, i would not be pressing this issue...but its ****ing cold! I am thinking about drilling a hole (what size, and how many) through the t-stat...any opinions on this?

ctm 12-27-2007 07:32 PM

I'm about out of ideas but are you orienting the t-stat with the air bleed hole on top. i'm not even sure it matters.


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