Electric Cooling Fan

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tylergrant2011

NAXJA Forum User

Location

Luverne

• Sep 20, 2015

• #1

I have an 87' MJ that ive noticed the electric cooling fan will not kick on. It will reach around 190 or 200F and still not kick on. Ive tested the fan by just hooking a jumper to the battery. Where is the relay located or does anyone have a suggestion of the problem?

 

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trippled

NAXJA Forum User

Location

colorado springs, co

• Sep 20, 2015

• #2

IIRC they only come on with ac or around 212 or 215.

 

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tylergrant2011

NAXJA Forum User

Location

Luverne

• Sep 20, 2015

• #3

Isnt 200 a little high?

 

IllianaXJ

NAXJA Forum User

Location

Southwest IN

• Sep 21, 2015

• #4

They are designed to run at/around 210. The efan will turn on somewhere around 215-220 or if the A/C is engaged.

 

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yossarian19

NAXJA Forum User

Location

Grass Valley, CA

• Sep 21, 2015

• #5

^^ Yep.
EFI era engines are designed to run hotter to get emissions down. If the fan wasn't on by 225 I'd look at it but just about every new ish vehicle I've worked on is supposed to run at 210, so the fan doesn't come on till some time after that. I think some Volvos I used to wrench on, the fan came on at 230* and the sucker had a 21 psi radiator cap.

 

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tylergrant2011

NAXJA Forum User

Location

Luverne

• Sep 21, 2015

• #6

While I'm at it what does the oil pressure supposed to read at idle with the engine warmed up

 

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yossarian19

NAXJA Forum User

Location

Grass Valley, CA

• Sep 21, 2015

• #7

More the better. I think the factory service manual says "at least 10 psi". I have heard guys say that they've driven for a decade or so with a 5 psi hot idle & no problems.
I think mine idled at 13 psi or so by the gauge, by 1200 RPM it was up to 40.
As long as oil pressure is present & noises aren't, I'd say your'e good. The Jeep 4.0 isn't real fussy.

 

87manche

NAXJA Forum User

Location

Ohio

• Sep 21, 2015

• #8

FSM says minimum 13 at idle.
37 above 2K rpms or some such.

the temp switch for the renix is in the radiator.
if there's an air pocket in there it won't work.

otherwise it seems normal. It won't turn on until it hits 215-220. If you want to change that, get an HO thermostat housing with the threaded boss, move temp switch to that and use a switch of your own temp choosing.

 

Johnnie Walker

Piece of Fish!

NAXJA Member

Location

WA state

• Sep 23, 2015

• #9

An older rule of thumb on oil pressure is a minimum of 10 psi/1k rpm. Only a mechanical gauge will tell you for sure what exactly your pressure is thought. Can rent from your local auto parts store, or buy from HF.