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Author Topic: Running Hot?  (Read 1474 times)

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Desert Bob

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Running Hot?
« on: October 09, 2007, 08:52:53 PM »
My 95 YJ seems to be running hot.  It hits 215* at a stop light and never drops below 210* even at night when it is cool.  The top hose is hot and under pressure but the bottom hose is cool to the touch.  The radiator seems newish and the fluid is clean.  Normally I see the temp rise and fall based on speed, etc.  Now it seem to just hover at 210* or above.  Would this be a bad thermostat or the water pump?
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lanulos89

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Re: Running Hot?
« Reply #1 on: October 10, 2007, 06:07:05 AM »
change the thermo stat for a 190* one
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Desert Bob

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Re: Running Hot?
« Reply #2 on: October 12, 2007, 01:23:02 PM »
The thermostat is a 195* one.  I can see it open at about 215* and then it stays open.  I would have expected it to open at 195*. I am going to replace it with another one and see what happens.  The odd thing is that the bottom radiator hose does not get hot.  Does this mean that coolant is not flowing through the radiator or that the thermostat is restricting the flow of coolant through the engine so that it gets warmer than it should?
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Offline Jeffy

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Re: Running Hot?
« Reply #3 on: October 12, 2007, 02:18:17 PM »
Quote from: Desert Bob on October 12, 2007, 01:23:02 PM
The thermostat is a 195* one.  I can see it open at about 215* and then it stays open.  I would have expected it to open at 195*. I am going to replace it with another one and see what happens.  The odd thing is that the bottom radiator hose does not get hot.  Does this mean that coolant is not flowing through the radiator or that the thermostat is restricting the flow of coolant through the engine so that it gets warmer than it should?

I highly recommend going with a Robertshaw thermostat.  They are well known for making thermostats and that's all they do.  Their stats are more expensive though.  Usually $10.  They are a better design with all copper/brass construction and are more accurate in that they open within a few degrees of the posted temp.

Does the tip hose get hot?  Not just warm but hot.  The cool bottom hose could mean one of two things, either there is no flow or your radiator is doing it's job.  You can test this a few ways.  One is to run the engine and feel the top hose.  When the thermostat opens it should get hot and stiff.  :uhoh:  The other way is to take the radiator cap off and watch it.  When it heats up it should start to overflow until the thermostat opens then you'll be able to see the coolant flowing.
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"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

Desert Bob

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Re: Running Hot?
« Reply #4 on: October 16, 2007, 04:26:36 PM »
I can see coolant flowing and the top hose does get hot and stiff  :whistle:

But after a while the coolant starts to bubble out like the thermostat has closed.  The temp always stays at 210* when idling.  I have ordered a Robert Shaw thermostat and gasket and hope to get it by this weekend.  All of the local stores had Stant thermostats and no gaskets.  So I figured it would be better to just wait for the good stuff.  Hope this works.
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Offline Jeffy

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Re: Running Hot?
« Reply #5 on: October 16, 2007, 04:41:56 PM »
Quote from: Desert Bob on October 16, 2007, 04:26:36 PM
I can see coolant flowing and the top hose does get hot and stiff  :whistle:

But after a while the coolant starts to bubble out like the thermostat has closed.  The temp always stays at 210* when idling.  I have ordered a Robert Shaw thermostat and gasket and hope to get it by this weekend.  All of the local stores had Stant thermostats and no gaskets.  So I figured it would be better to just wait for the good stuff.  Hope this works.

I got fed up with Stant when I replaced mine the first time and a week later the stant broke.  The engine would heat up till around 230-40 then blow out and force open the thermostat.  Then it would suddenly drop to 195 till it lost enough pressure that the thermostat closed again.  What a PITA.
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"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

Offline brokenwrist21

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Re: Running Hot?
« Reply #6 on: October 24, 2007, 10:44:00 PM »
jeep engines have this really weird thing of forming air bubbles that get stuck in the cooling system. they all do it, what i do is let the engine run until it starts getting warm then vent the cap, not remove it but vent it so it releases the pressure, but not coolant. and keep an eye on the temp gauge. do this for a few minutes untill it's running where it should. i have a stant superstat thermostat that if it ever fails will fail in the open position not closed. i've always had good look with stant myself.
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'93 yj 4in rubicon express lift, 33" bfg mud terrains, yella terra roller rockers, 4.0l throttle body, rv cam, k&n air filter, yukon axles and gears, detroit locker, aluminum radiator, msd 8.5mm super conductor wires, full syn. fluids.

Offline chardrc

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Re: Running Hot?
« Reply #7 on: October 25, 2007, 05:54:15 PM »
not to highjack the thread. but i have 1 quick cooling question. a week ago i was tinkering under the hood of my jeep and noticed there was almost no coolant in the reservoir. so i went to ope the cap to see if the radiator was still full. and when i twisted the cap coolant came out.. it was still slightly pressurized which is weird cuz i hadn't started it in over a week. does this mean i have a bad radiator cap or am i just crazy.
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1990 YJ 4cly, ax5, 2.5 inch BDS lift, 31 MTr\'s,  Powertrax-lockers all around, track-bars removed, boomerang shackles, warn m8000 winch, electric fan. [sold but not forgotten]

2007 jk Rubicon 2dr

Offline Jeffy

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Re: Running Hot?
« Reply #8 on: October 25, 2007, 05:55:56 PM »
Quote from: chardrc on October 25, 2007, 05:54:15 PM
not to highjack the thread. but i have 1 quick cooling question. a week ago i was tinkering under the hood of my jeep and noticed there was almost no coolant in the reservoir. so i went to ope the cap to see if the radiator was still full. and when i twisted the cap coolant came out.. it was still slightly pressurized which is weird cuz i hadn't started it in over a week. does this mean i have a bad radiator cap or am i just crazy.

Radiator cap isn't working properly or got stuck.  I've had that happen.  It heats up then sucks the res. dry and hold it pressurized inside the cooling system.
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"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

Desert Bob

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Re: Running Hot?
« Reply #9 on: October 26, 2007, 11:58:47 AM »
Still waiting for my Robert Shaw thermostat from Quadratec.  They say it will be delivered next week.  This week-ends project is my new Rubicon Express 2.5" lift kit.
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Offline jfrabat

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Re: Running Hot?
« Reply #10 on: October 27, 2007, 08:02:06 PM »
I will be installing one tomorrow as well, but for the opposite reaason; my jeep runs too cold!
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'94 YJ 2.5L with 4" RE lift, Superwinch EPi9.0, FoMoCo e-Fan, SD30 and SD35 w/ARB-5.13, 165A alt., 33" BFG KM2 on 15" AR wheels, Sony sound system, Pavement Ends Hardtop, Hydroboost

Offline jfrabat

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Re: Running Hot?
« Reply #11 on: October 28, 2007, 05:59:36 PM »
installed the thermostat, and the jeep is running great...  Temp needle is now glued to 195* (where as before it would drop down to 180* or lower when on the highway).
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'94 YJ 2.5L with 4" RE lift, Superwinch EPi9.0, FoMoCo e-Fan, SD30 and SD35 w/ARB-5.13, 165A alt., 33" BFG KM2 on 15" AR wheels, Sony sound system, Pavement Ends Hardtop, Hydroboost

Desert Bob

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Re: Running Hot?
« Reply #12 on: November 03, 2007, 06:36:01 PM »
Fixed. Put in a new 195* Robert Shaw thermostat, new upper and lower hoses (the date on them said 1995 wow) and new Fan Clutch.  Runs at 195* with some peaks just below 210* after going up a large hill in third gear at 55mph.  Nice.  Now if I could just fix my idle and clutch issues I would be cooking.
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Jesse-James

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Re: Running Hot?
« Reply #13 on: November 03, 2007, 08:05:22 PM »
Thanks for posting back. So many times threads go unanswered because the OP forgets.  :thumb:
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Offline Jeffy

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Re: Running Hot?
« Reply #14 on: November 03, 2007, 08:26:35 PM »
Quote from: Desert Bob on November 03, 2007, 06:36:01 PM
Fixed. Put in a new 195* Robert Shaw thermostat, new upper and lower hoses (the date on them said 1995 wow) and new Fan Clutch.  Runs at 195* with some peaks just below 210* after going up a large hill in third gear at 55mph.  Nice.  Now if I could just fix my idle and clutch issues I would be cooking.

Sounds like you're set!  The Robert shaws are nice.  Probably out live the engine.  :thumb:
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Youtube Channel: https://www.youtube.com/channel/UCZNlr60GXH5OlKIFrT7P6mg
My Jeep: http://4bangerjp.com/forums/index.php?topic=2783.0
"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."
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