89 XJ coolant flush and cooling system upgrade - Page 2 - JeepForum.com
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post #16 of 33 Old 07-21-2017, 10:36 PM
mattrowe
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Should the fan come on regardless of weather the ac is turned on, or only when the ac is turned on.
My 90 seems to come on only when the ac is on.
Just flushed and refilled.
I looked but did not see a vent for the closed system.
My manual did not say anything about venting or purging it either.

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post #17 of 33 Old 07-21-2017, 10:58 PM
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Originally Posted by mattrowe View Post
Should the fan come on regardless of weather the ac is turned on, or only when the ac is turned on.
My 90 seems to come on only when the ac is on.
Just flushed and refilled.
I looked but did not see a vent for the closed system.
My manual did not say anything about venting or purging it either.
The fan should always kick on if your engine temp gets high enough, it will always be on when your AC is running. If its not kicking on when temp gets high enough, there's probably a sensor, fuse, relay or switch that went bad.

According to spec sheets it should be kicking on at about 220F, give or take 5.

Definitely purge the air from the system. Just run it with the cap off and keep adding coolant to the rad until it overflows. Make sure the reservoir is full too.

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post #18 of 33 Old 07-21-2017, 11:12 PM
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Thanks dc, i will check again and see if it comes on a little higher than 210.
Also,mine has the closed system on it.
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post #19 of 33 Old 07-22-2017, 06:50 AM
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I think 218*F is when the radiator switch closes and signals the relay to turn the fan on.

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post #20 of 33 Old 07-22-2017, 10:47 AM
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I think 218*F is when the radiator switch closes and signals the relay to turn the fan on.
That is what I read too, but I wasn't sure if that was across all years, I just rounded up to the nearest 5F, since unless you've the temp gun you won't really be able to tell on your engine anyways.

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post #21 of 33 Old 07-22-2017, 11:13 AM
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Quote:
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That is what I read too, but I wasn't sure if that was across all years, I just rounded up to the nearest 5F, since unless you've the temp gun you won't really be able to tell on your engine anyways.
How could you tell by the dash gauge anyway? LOL.

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post #22 of 33 Old 07-22-2017, 06:43 PM
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I flushed my system but even in the manual (haynes) it just says to fill the bottle, and run it.
On all other vehicles ive worked on there is an allen head screw or some thing to loosen to purge the system.
Now my fan does not come on unless i turn on ac.
I wonder if air still present.
Closed system tank is full at firewall.
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post #23 of 33 Old 07-22-2017, 06:48 PM
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Quote:
Originally Posted by mattrowe View Post
I flushed my system but even in the manual (haynes) it just says to fill the bottle, and run it.
On all other vehicles ive worked on there is an allen head screw or some thing to loosen to purge the system.
Now my fan does not come on unless i turn on ac.
I wonder if air still present.
Closed system tank is full at firewall.
Check your coolant temp sensor. Its different than the thermostat.

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post #24 of 33 Old 07-22-2017, 07:13 PM
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Ok. Mine should have 3 sensors right.
back of head for ecu air/fuel mix.
block for gauge
radiator for fan
My son was driving it and said twice this week it lost power, but then picked up again on its own.
Maybe fan sensor and ecu sensor are going bad.
Mine a renix. 90
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post #25 of 33 Old 07-22-2017, 07:19 PM
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Originally Posted by mattrowe View Post
Ok. Mine should have 3 sensors right.
back of head for ecu air/fuel mix.
block for gauge
radiator for fan
My son was driving it and said twice this week it lost power, but then picked up again on its own.
Maybe fan sensor and ecu sensor are going bad.
Mine a renix. 90
I'd have to check the manual to be sure. There is definitely one in the back of the block. Most cars only have one.

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post #26 of 33 Old 07-22-2017, 08:28 PM
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ok, i will look at mine again
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post #27 of 33 Old 07-22-2017, 08:40 PM
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Quote:
Originally Posted by mattrowe View Post
Ok. Mine should have 3 sensors right.
back of head for ecu air/fuel mix.
block for gauge
radiator for fan
My son was driving it and said twice this week it lost power, but then picked up again on its own.
Maybe fan sensor and ecu sensor are going bad.
Mine a renix. 90
I dont think it would help with your radiator issue , but if your renix is acting up, google cruisers renix tips on this site
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post #28 of 33 Old 07-22-2017, 09:28 PM
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Going to head over to cruisers site, been there before, thanks.
Still have engine ground to redo, and to reground ac/heater fan. Blower.
Did all the other grounds, going to add a better one from firewall to intake manifold.
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post #29 of 33 Old 07-22-2017, 10:25 PM
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Back of head is for the dash gauge. Block is for ECU. On radiator turns on the e-fan.

If your coolant pressure tank's cap is DOA it will overheat. The bottles and caps nowadays are C.R.A.P.

Chinese Replacement Auto Parts.

try using a Napa 703-1396 cap on the pressure bottle.

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post #30 of 33 Old 07-25-2017, 01:09 PM Thread Starter
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Quote:
Originally Posted by mattrowe View Post
Should the fan come on regardless of weather the ac is turned on, or only when the ac is turned on.
My 90 seems to come on only when the ac is on.
Your coolant sensor in the radiator may not be function correctly. It should be on the drivers side, half way up the radiator tank. You should be able to test to see if it has failed by disconnecting it, and use a jumper wire on the connector from the wire harness side (not the side going to the sensor). With that jumppered, the fan should start running as soon as you turn the key to 'run'. If it does, then that sensor needs to be examined/replaced.

Quote:
Originally Posted by mattrowe View Post
I flushed my system but even in the manual (haynes) it just says to fill the bottle, and run it.
On all other vehicles ive worked on there is an allen head screw or some thing to loosen to purge the system.
Now my fan does not come on unless i turn on ac.
I wonder if air still present.
Closed system tank is full at firewall.
Some recommend filling the closed system from the upper radiator hose. I never tried this since I changed to the open system. Also check out this thread for ideas on the renix closed system:
https://www.cherokeeforum.com/f2/bur...-system-19001/

1989 stock 2 door LTD XJ w/ 4.0L + AW4
and 4 Volvo 240s
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