Topic: 2.5 Running Hot

[Kman]

Well we swapped a '97 2.5 into my wifes '93 YJ. I used the '93 distributor, coil, sensors, fuel rail and injectors. I swapped on a 4.0 throttle body(used the 2.5's AIS and throttle position sensor). We also added a 9 lb inertia ring. It fired right up and runs strong except it is running hot. Once it has been running it fluctuates back and forth from 210 degrees to the red line. We installed a new 195 degree thermostat-no change. Installed a new water pump-no change. Swapped radiators with our '89 Lerado-no change....The temp sender in the rear of the head is also new. Anyone have any ideas??

[sharpxmen]

Well we swapped a '97 2.5 into my wifes '93 YJ. I used the '93 distributor, coil, sensors, fuel rail and injectors. I swapped on a 4.0 throttle body(used the 2.5's AIS and throttle position sensor). We also added a 9 lb inertia ring. It fired right up and runs strong except it is running hot. Once it has been running it fluctuates back and forth from 210 degrees to the red line. We installed a new 195 degree thermostat-no change. Installed a new water pump-no change. Swapped radiators with our '89 Lerado-no change....The temp sender in the rear of the head is also new. Anyone have any ideas??

could be the fan clutch if your thermostat is new and you  have coolant flow. i did see new thermostats fail but since it's doing the same thing as with the previous one it;s unlikely. One thing to check is if you get pressure in the upper hose (squeeze it while revving up) when it shows over 200 temp, if you do then most obvious would be the clutch. you could also stop the engine and see if the clutch is "holding" more than when cold, if it's spinning freely when hot then that's the problem (or at least one of the problems).

[Jeffy]

I'm going to say it's the thermostat.  What's probably happening is the thermostat is stuck closed it builds pressures and blows the thermostat open.  The temps drop suddenly then the temps start to rise again.

You could test this by taking out the thermostat and running it.  Otherwise you could watch the radiator with the cap off.  You should be able to see the flow.  It will overflow but once the thermostat opens it should settle down.

I highly recommend getting a Robershaw Thermostat an not a cheap Stant.  The RobertShaw's are brass/copper and are built to stricter specs.

[Kman]

Well we bought a new NAPA radiator today, 210 is the top temperature. My wife told me as long as she has owned this Jeep(3rd engine) it has always run 210 degrees with all engines.  What are your 2.5 engines running for average temperatures?

[Kman]

I did check the fan, it didn't seem any different between cold and hot. We did run the TJ 2.5 fan originally but I didn't check it cold/hot. Might throw it back on tommorrow and try it. I have read a lot about how important it is to run a 195 degree thermostat but thinking about trying a 180 degree unit to see if it then runs at 195...I'll have to search and see where I can get a RobertShaw thermostat and maybe try a couple of them.

[Jeffy]

I did check the fan, it didn't seem any different between cold and hot. We did run the TJ 2.5 fan originally but I didn't check it cold/hot. Might throw it back on tommorrow and try it. I have read a lot about how important it is to run a 195 degree thermostat but thinking about trying a 180 degree unit to see if it then runs at 195...I'll have to search and see where I can get a RobertShaw thermostat and maybe try a couple of them.

Stick with a 195* thermostat.  The Jeep should run anywhere between 195*-210*  Some run hotter, some a bit cooler.  I wouldn't really worry too much as long as it's consistent and not actually going into the red.  Tollerances within the thermostat, sender unit and gauge could be the problem.

Bit if it's bouncing off red line to 195* then it's more then likely the thermostat.  Should cost $10 but they are well worth it.

[Kman]

Jeffy who do you buy your Robert Shaw thermostats through?

[grumpygy]

Right after I started mine back up after a long period of not using it.  And right after doing work on the heater core so I had drained all the fluid out then replaced it.   I had about the same problem.  It was really running hot.  But then it burped and the air bubble that was in it came out.  Seems to be running great except the new leak in the heater core.   Dropping in a new one again.  So will go reread that FAQ on heater core changing.  Think this time it will be much easier.

[sharpxmen]

grumpy might have it right, let the thermostat open with the radiator cap off and add coolant, might be an air bubble but as long as it opens and you add coolant will go away (the radiator top tank is above the thermostat housing)

make sure you take the cap off with engine cold so it doesn't blow hot coolant out (i'm sure you know but just in case).

[Kman]

Yep when we put the new radiator in we pulled it on to a dirt pile in the yard so the front was lifted and cap to the high side and let it warm up. Several large air bubbles came out and had to ad fluid. The heater is blowwing AWESOME hot air! On the second run up the dirt road across the street we pulled up on a couple of dirt piles and let it run also. I would still like to get it under the 210 mark if I could. It is suppossed to hit 80 degrees here Sunday so I'll like to see the temp then!! I searched the internet and found something interesting about temp senders...seems the factory senders are much more acurate than aftermarket ones...might have to see if I can get one from the dealer.

[grumpygy]

I had let it cool .  Took the cap off to see if I could see anything like Bubbles or anything.  After a bit it had warmed up enough for the thermostat to open and that's when it Burped.  Topped it back off and it worked great.

  Till I decided I didn't like on heater hose so I changed it.  Must have been a little too rough putting it on and busted the core.

[Johnny99TJ]

Well maybe I can offer some things to check as I chased down my overheating issues for 2 months.
* Lower Radiator hose collapsing? Let motor heat up and elevate RPMs and inspect lower hose to see if it will collapse. If so replace with a factory spring installed hose.
(Note if the lower hose will collpase, you more than likely have a clogged radiator)

* Cracked cylinder head? I had a cracked head that was allowingthe coolant to burn off thru the exhaust without detection. It was only found after the head was removed and hot tanked for cleaning. It was clear then that there was a very slight crack identified by what looked like a lead pencil line on casting. Even had a motor pressure check wich did not indicate this cracked head.

*Thermostat? Not often occuring but could have a bad thermostat. Replace with factory thermostat (prob 195*)  a cooler thermostat will not help your jeep run cooler as many people think...

*Air pockets in cooling system? Again doesnt happen often but deff can play a part with temp issues. Allow motor to warm up and allow system to burp thru at fill cap...top off.

My 2.5L was the result of a cracked head and a clogged radiator. It now runs consistant 205-210* and on suuuumetimes it will hit 215* but this is in 90* Florida heat with a winch filling the grill. It started with the temp gauge jumping up and down...after a lot of time it was found it was the head. After replacing that, it was still jumping temp....found clogged radiator....after that its all good to go. Hope this helps....

[Jeffy]

Jeffy who do you buy your Robert Shaw thermostats through?

QTech usually.