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Unread 07-12-2013, 10:05 AM   #1
Camj37
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Overheating out of ideas

I have a 91 yj with 150xxx I replaced the radiator and cap, new 180 t-state, high flow t-state housing, new high flow water pump with counter clock rotation, and electric fan. Hoses aren't Collapsing. I had a head gasket check came back negative. I'm currently out of viable ideas. My normally trusted shop couldn't find anything after I gave up and sent it in.

My timing is off by a degree (or Presumed to be), there's a little knock like noise. And I think I need new injectors. But could these cause an overheating problem.

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Unread 07-12-2013, 10:24 AM   #2
iflypa28
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Just brainstorming here to try and help you out. Sorry if some of my questions seem stupid. When does it overheat, just idling or while driving at speed? Or both? I assume the electric fan is a mod. Is it blowing in the correct direction. It is possible on most for them to run backwards if wired backwards. Did it just start overheating out of the blue or did it start after some sort of repair or mantinence? I have a 5.9L grand cherokee as well as a yj and it has a factory electric fan. It had a bad connection and was running intermittently and overheating. Took me for ever to figure that out. Come to think of it, its a two speed fan as many are. Any chance yours is only running on low speed? That would do it.
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Unread 07-12-2013, 10:41 AM   #3
instg8tor
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How is your timing off by a degree - its computer controlled for fuel injected 4.0L's.
Have you tried returning back to the engine driven fan? Would be worth trying to rule out any issue with electric fans.
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Unread 07-12-2013, 10:45 AM   #4
Luuca
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It would help if you describe the "how and When" its overheating.

Is it climbing at idle, but OK at speed? Usually attributed to cooling fan, leak in system, bad water pump, Airlock in upper hose.


Is it OK at idle, and slower speeds, but climbs at speed? Usually indicates a clogged radiator, pressure leak, dirty or inefficient radiator.


Things to check IMO:

That knock - exhaust leak at the manifold could cause some issues and sound like a knock. does the knock go away after it heats up? or is it fairly constant?
That Electric fan - Does it have a shroud? Facing the right direction? How is it controlled? tested the temp sensor?
That T-stat - tried removing it and testing it in a pot of boiling water to ensure it's not faulty?
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Unread 07-12-2013, 10:49 AM   #5
Camj37
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Never overheats at idle takes a long time at city speeds but fairly quick at highway speed.
The fan is a mod but it does blow in the right direction it's a puller fan but when I think about it is a 2 speed but the second speed never kick in.
The problem started either after I changed my t-state for the first time or after my fan control went out and I boiled over (both happened right after the other) but I live in AZ and it started to happen when the temp started to rise(100-120 normally)
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Unread 07-12-2013, 10:56 AM   #6
iflypa28
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I have had terrible luck with new t-stats. I've replace several only to have to replace them again. Maybe it's not opening all the way. I would test it in a pot of boiling water as suggested. It's not likely its the fan if it doesn't overheat at idle. There are some other good suggestions here too.
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Unread 07-12-2013, 10:59 AM   #7
iflypa28
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I forgot to mention that I now invest in the high dollar t-stats not just the cheapest one I can get. There only a few bucks more, but I would be never get a fail-safe one!
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Unread 07-12-2013, 11:14 AM   #8
Luuca
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Quote:
Originally Posted by Camj37 View Post
Never overheats at idle takes a long time at city speeds but fairly quick at highway speed.
The fan is a mod but it does blow in the right direction it's a puller fan but when I think about it is a 2 speed but the second speed never kick in.
The problem started either after I changed my t-state for the first time or after my fan control went out and I boiled over (both happened right after the other) but I live in AZ and it started to happen when the temp started to rise(100-120 normally)
When was the radiator last flushed and refilled?
How old is the radiator?

I had the same exact issue with our 91 YJ and it was a clogged rusty bad radiator. Replaced it and no more issues.
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Unread 07-12-2013, 11:16 AM   #9
Siva283
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First you got the wrong Tstat it should be a 195. Your other issue lies in your choice of fans. Seems to me it is impeding air flow at speeds.
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Unread 07-12-2013, 11:24 AM   #10
Camj37
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My t-state came with my high flow polished powdercoated t-state housing it was a pretty penny for the set.
As for the knock it gets worse as it heats up once it hits a point it doesn't get worse. But when I drive down the highway when I take my foot off the gas it's rough and pushing it again its rough until I hit 2000rpm.
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Unread 07-12-2013, 11:30 AM   #11
Camj37
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The radiator and rad cap is brand new so is the fluid and I had it vaccum filled to insure all air was out.
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Unread 07-12-2013, 02:01 PM   #12
Luuca
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Quote:
Originally Posted by Camj37 View Post
The radiator and rad cap is brand new so is the fluid and I had it vaccum filled to insure all air was out.
You have replaced the entire cooling system after your fan sensor boiled you over and now you continue to boil over.

On top of that, you now have a knock in the engine and rough running below 2000 rpm.

Sell it. Buy a Honda.

J/K

Are you sure you don't have a head gasket issue after boiling over? Sure sounds like it's internal.
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Unread 07-12-2013, 04:48 PM   #13
Sparrows
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Quote:
Originally Posted by Luuca View Post

You have replaced the entire cooling system after your fan sensor boiled you over and now you continue to boil over.

On top of that, you now have a knock in the engine and rough running below 2000 rpm.

Sell it. Buy a Honda.

J/K

Are you sure you don't have a head gasket issue after boiling over? Sure sounds like it's internal.
Funny, sounds like my Jeep. Extra funny cause literally this morning my father rd me I should sell it and get a Honda lol.

I was like"nah, I'd rather just throw a v8 in it." Haha.

Cheers
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Unread 07-13-2013, 08:12 AM   #14
Camj37
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It's not rough in the normal sense it's pretty hard to explain. It's only rough like a weird vibration in the peddle only after driving on the highway for a while and when I take my foot off and back on. Once I get off the highway and start from idle its not there anymore.
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Unread 07-13-2013, 09:13 AM   #15
jsawduste
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Unlike most here on this board I DO NOT LIKE ELECTRIC FANS. Yes I have run them and I go back to mechanical every time. The fallacy of extra power is just that a fallacy. The extra parasitic drag of the alternator supplying the amperage to run the fan outweighs any power advantage. When the engine turns the fan turns. What could be simpler or more reliable ?

The factory shroud and fan asm with the clutch should be your first investment. Little known fact is that the YJ`s that came with factory AC have a more aggressive fan pitch. If you think you need more airflow then I`d suggest one of those.

New radiator but what material and how efficient ? Do you have a winch or other item blocking the grille ?

I still do not understand your knocking issue. It may be the root cause or it might be something totally different.
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