Author Topic: Overheating issues: FINAL UPDATE.  (Read 2045 times)

Offline R3

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Re: Overheating issues
« Reply #15 on: September 14, 2020, 08:33:01 AM »
Blocked Cat will cause  you overheat issues. Glad then found that  your performance should have  improved as well.  When the  radiator was flushed  was there still crud coming out?

If a motor is hot and you shut it down for a few minutes  it will get hotter.  Yes  since there is no circulation going on  it will get hotter.  If there is scale in the engine  the cooling properties will be greatly reduced.  From the previous posts it sounds like that could be an issue.  another check you can do it find a hot spot is use a digital IR  thermometer, check the  block  cylinder at a time to see where it is hot and normal... hot spots  usually result in a poor circulation or  rusty  passages not passing coolant. 

Given the condition of coolant  when first flushed out it is highly possible that  the block has some serious scale  in it and could be clogging coolant passages.

An idea ,  change out the freeze plugs, this will give you an idea of the condition  inside the water passages. it is rather simple to do and can be done with  at home tools. If it is seriously  crusty in there, your cooling issues will persist.
 I believe there are some  pour in  chemicals to help  remove or  defeat the scale.   

Last stop would be pull the head and look inside.  Check with Gr8dain he might have another 4.0  just laying around.... could use a few oil seals...

Cheers
Cheers

17 JKURR Daily/rock crawler/overland
2013 Victory XCT hot rod.

Offline XJBayne

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Re: Overheating issues
« Reply #16 on: September 16, 2020, 11:44:03 PM »
Blocked Cat will cause  you overheat issues. Glad then found that  your performance should have  improved as well.  When the  radiator was flushed  was there still crud coming out?

If a motor is hot and you shut it down for a few minutes  it will get hotter.  Yes  since there is no circulation going on  it will get hotter.  If there is scale in the engine  the cooling properties will be greatly reduced.  From the previous posts it sounds like that could be an issue.  another check you can do it find a hot spot is use a digital IR  thermometer, check the  block  cylinder at a time to see where it is hot and normal... hot spots  usually result in a poor circulation or  rusty  passages not passing coolant. 

Given the condition of coolant  when first flushed out it is highly possible that  the block has some serious scale  in it and could be clogging coolant passages.

An idea ,  change out the freeze plugs, this will give you an idea of the condition  inside the water passages. it is rather simple to do and can be done with  at home tools. If it is seriously  crusty in there, your cooling issues will persist.
 I believe there are some  pour in  chemicals to help  remove or  defeat the scale.   

Last stop would be pull the head and look inside.  Check with Gr8dain he might have another 4.0  just laying around.... could use a few oil seals...

Cheers
There was, but after 3 flushes, I believe its pretty clean.  But like you said, there may be some heavy scaling.  My guess is my first flush wasn’t good enough and it clogged up coolant passages in the block.  I’m not experiencing any of the typical head gasket symptoms.

I’m gonna go ahead and get a IR thermometer and check some temps out and go from there.  The shop that found the blocked cat is closed until the 22nd.  I need to see what the best option is.  Either way, I really think the head needs to be pulled.  Question is, is it really worth doing all that, or just swapping out the engine.  And if we’re talking engine swaps, I think its worth considering a reman as well.  Peace of mind certainly has a value.  Gotta feel my mechanic out I suppose.
98 XJ

Offline R3

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Re: Overheating issues
« Reply #17 on: September 17, 2020, 08:46:38 AM »
Before going to all the trouble of  re-powering you might consider
1) pulling a freeze plug of two  and bore scoping the  coolant passage to see how bad it really is.

2) use the IR thermometer to check for uniform temps across the head. if the temps are  uniform  I would not suggest pulling the head.

3) pull the cat  and replace with a test pipe... run the rig a bit and monitor the temps if they still go high then you need to look deeper into the cooling system
Cheers

17 JKURR Daily/rock crawler/overland
2013 Victory XCT hot rod.

Offline XJBayne

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Re: Overheating issues
« Reply #18 on: September 17, 2020, 02:57:09 PM »
Before going to all the trouble of  re-powering you might consider
1) pulling a freeze plug of two  and bore scoping the  coolant passage to see how bad it really is.

2) use the IR thermometer to check for uniform temps across the head. if the temps are  uniform  I would not suggest pulling the head.

3) pull the cat  and replace with a test pipe... run the rig a bit and monitor the temps if they still go high then you need to look deeper into the cooling system
I will mention this to him and see what he thinks our next best attack is.  I‘m really well outside my comfort zone doing any more work on it at this point.
98 XJ

Offline RFH_98TJ

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Re: Overheating issues
« Reply #19 on: September 18, 2020, 07:56:10 AM »
How about sending an oil sample out to see if it comes back with coolant listed as being in it.  I still think your radiator needs replacing.  I wouldn't pull the head yet.
98 TJ 4.0 Sport 5-speed - 4" lift on 35s, 4.56 on D30 with Lock Right and Ford 8.8 LS, Lots of welding

- Frank

Offline R3

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Re: Overheating issues
« Reply #20 on: September 18, 2020, 03:22:00 PM »
Before going to all the trouble of  re-powering you might consider
1) pulling a freeze plug of two  and bore scoping the  coolant passage to see how bad it really is.

2) use the IR thermometer to check for uniform temps across the head. if the temps are  uniform  I would not suggest pulling the head.

3) pull the cat  and replace with a test pipe... run the rig a bit and monitor the temps if they still go high then you need to look deeper into the cooling system
I will mention this to him and see what he thinks our next best attack is.  I‘m really well outside my comfort zone doing any more work on it at this point.

Most automotive issues are  really just small things going  wrong and looking like a major issue.  Your Cooling issue  might just be as easy as replacing the  clogged cat, a new radiator cap, or  adding a little water wetter to the coolant.  4.0L motors run hot to start with so the margin for  error is increased.  You sound like you have done all teh right things with respect the cooling system.  Get the cat fixed  and you might just be on you way.

Lots of folks here on the forum  work on their own stuff. we are happy to lend a hand if needed.  If you have a good shop  that you trust then you are in good hands.

Work the simple stuff first  a little at a time  before going to extremes of  new engines.

Cheers
Rob
Cheers

17 JKURR Daily/rock crawler/overland
2013 Victory XCT hot rod.

Offline XJBayne

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Re: Overheating issues
« Reply #21 on: September 22, 2020, 07:07:18 PM »
How about sending an oil sample out to see if it comes back with coolant listed as being in it.  I still think your radiator needs replacing.  I wouldn't pull the head yet.
I put a new Mishimoto aluminum radiator in it.  If I had coolant in the oil, wouldn’t it be milky?  Sending out an oil sample isn’t a bad idea though.  Thanks for the advice.

Before going to all the trouble of  re-powering you might consider
1) pulling a freeze plug of two  and bore scoping the  coolant passage to see how bad it really is.

2) use the IR thermometer to check for uniform temps across the head. if the temps are  uniform  I would not suggest pulling the head.

3) pull the cat  and replace with a test pipe... run the rig a bit and monitor the temps if they still go high then you need to look deeper into the cooling system
I will mention this to him and see what he thinks our next best attack is.  I‘m really well outside my comfort zone doing any more work on it at this point.

Most automotive issues are  really just small things going  wrong and looking like a major issue.  Your Cooling issue  might just be as easy as replacing the  clogged cat, a new radiator cap, or  adding a little water wetter to the coolant.  4.0L motors run hot to start with so the margin for  error is increased.  You sound like you have done all teh right things with respect the cooling system.  Get the cat fixed  and you might just be on you way.

Lots of folks here on the forum  work on their own stuff. we are happy to lend a hand if needed.  If you have a good shop  that you trust then you are in good hands.

Work the simple stuff first  a little at a time  before going to extremes of  new engines.

Cheers
Rob
I went ahead and had the cat replaced.  Tried it out about a week ago and it still overheated.  I’ll keep you all in the loop.
98 XJ

Offline RFH_98TJ

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Re: Overheating issues
« Reply #22 on: September 23, 2020, 07:33:51 AM »
I re-read the entire post again.  I didn't see the part earlier where you said you replaced the radiator with a Mishimoto.  On TJs at least, OEM is the best choice and aftermarket radiators leads into the exact situation you are currently in.  They just don't have enough cooling capacity.  I also know you replaced the cap (or it came with one).  I think I would buy a new "good" name brand and replace it since they are inexpensive.  The part about it boiling over once you shut it down is usually linked to a bad cap.  The coolant getting very hot after shutting down is actually normal from hot spots in the block, but a good cap keeps it from boiling over.

Coolant in the oil would not necessarily be milky in small volumes but would show up in a test.  A small combustion leak into a coolant passage can easily overheat the coolant to where the cap can't manage it any longer.

Are you mixing (if you're mixing) the coolant correctly?  50/50 antifreeze vs. water is pretty much the ratio for our region.  The more water, the better the heat exchange but we need to worry about freezing.  The water wetter stuff works, but that should not be a repair method for OEM parts.  I use it in all my vehicles to "help" things stay cool.

You have electric fans right?  Re-verify that they both come on once the engine is hot.  The AC should make the secondary fan come on at any time if I recall, but a hot engine temp should also make it come on.  Read up on it.  The primary might be a two-speed and the secondary may just be an on/off.  If the primary is cutting out on hi that could be a big problem.  Or, sometimes the fans are linked together and the controller runs them both at the same speed either hi or lo.  Make sure they are both running when you see it start to over heat.  Do the fans use their own heat sensor and the gauge uses a different one?  Going down a rabbit hole now.....
98 TJ 4.0 Sport 5-speed - 4" lift on 35s, 4.56 on D30 with Lock Right and Ford 8.8 LS, Lots of welding

- Frank

Offline XJBayne

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Re: Overheating issues
« Reply #23 on: September 23, 2020, 04:00:20 PM »
I re-read the entire post again.  I didn't see the part earlier where you said you replaced the radiator with a Mishimoto.  On TJs at least, OEM is the best choice and aftermarket radiators leads into the exact situation you are currently in.  They just don't have enough cooling capacity.  I also know you replaced the cap (or it came with one).  I think I would buy a new "good" name brand and replace it since they are inexpensive.  The part about it boiling over once you shut it down is usually linked to a bad cap.  The coolant getting very hot after shutting down is actually normal from hot spots in the block, but a good cap keeps it from boiling over.

Coolant in the oil would not necessarily be milky in small volumes but would show up in a test.  A small combustion leak into a coolant passage can easily overheat the coolant to where the cap can't manage it any longer.

Are you mixing (if you're mixing) the coolant correctly?  50/50 antifreeze vs. water is pretty much the ratio for our region.  The more water, the better the heat exchange but we need to worry about freezing.  The water wetter stuff works, but that should not be a repair method for OEM parts.  I use it in all my vehicles to "help" things stay cool.

You have electric fans right?  Re-verify that they both come on once the engine is hot.  The AC should make the secondary fan come on at any time if I recall, but a hot engine temp should also make it come on.  Read up on it.  The primary might be a two-speed and the secondary may just be an on/off.  If the primary is cutting out on hi that could be a big problem.  Or, sometimes the fans are linked together and the controller runs them both at the same speed either hi or lo.  Make sure they are both running when you see it start to over heat.  Do the fans use their own heat sensor and the gauge uses a different one?  Going down a rabbit hole now.....
My apologies, I must have shared the Mishimoto radiator info in my head lol.

Originally I had replaced the cap and it seemed to solve the problem, but it boiled over again on a second drive with the stock radiator. I replaced the thermostat, blew out again.  That’s when I completely overhauled the system, all the front components are new.

I think I will order a blackstone kit.  Currently its back at the mechanic and he’s diving deeper into it, said he wanted to run a leak down test and some other things. He said its possible one of the cylinders could be leaking into the coolant and creating an air pocket behind the thermostat to keep it shut.

I’ve just been using the 50/50 to keep things simple.

I have one mechanical fan with a clutch and one electric fan.  I can confirm they both are running when hot and no A/C is running.  Typically when I turn the A/C on, the electric fan kicks on no matter what temperature its at.  As far as the high low speed, I’d have to look into that.  But OCD Offroad fully checked the fans as well.

I was able to learn more about the temp gauge on the dash.  Basically if it reaches a predetermined “critical” temp, it spikes the gauge for you to stop.  I had significantly less notice on blow outs.

On my drive after replacing the cat it did not boil out the coolant like before.  It just got hot.  So I think that part fixed the blow outs, which makes the air pocket scenario seem reasonable.  It has blown out overheated 4 or 5 times now.  It’s possible I did a number on it trying to diagnose it and changing out parts.

Thank you for your wealth of information.  I’m gonna look into the fan operations now and hopefully hear from my mechanic buddy in a little.
98 XJ

Offline RFH_98TJ

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Re: Overheating issues
« Reply #24 on: September 24, 2020, 07:47:21 AM »
I'm not saying to replace the fan clutch - that's just throwing parts at the problem.  But, here is some food for thought that happened to me a few years ago.

We pulled a small utility trailer with AC on from OBX thru the swamps along the coast to MB on a hot July 4th weekend, over 102 degrees.  At higher speed (65-75 mph) the TJ would set the gauge off and peg it.  Like you discovered, that's what the computer will do.  Just driving around town wherever all day, everything was fine.  The general consensus (most people will say) is a fan clutch has NO impact at higher speed as the air simply flows thru the radiator at speed by forward motion.  That's not exactly true.  What was really going on was that the fan was slipping so bad at high rpm, it was a hinderance to air going thru the radiator and caused it to overheat.  As long as I stayed at no more than about 61 mph, it was fine.  I got to our destination a little later than i wanted and put a new fan clutch on the next day - and nothing else.  It was fine after that.

Is the electric fan OEM?  Are they side-by-side or is one blowing into the other?  I can't remember exactly how the XJs do the fan set-up.  I'm wondering if the configuration is slowing air down at higher speed?  If its not OEM (meaning someone added it as extra cooling), I would remove it and see what happens.

What year is this XJ?
98 TJ 4.0 Sport 5-speed - 4" lift on 35s, 4.56 on D30 with Lock Right and Ford 8.8 LS, Lots of welding

- Frank

Offline XJBayne

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Re: Overheating issues
« Reply #25 on: September 25, 2020, 06:37:51 PM »
Wow, how about that.  Its definitely worth looking into tho.  It could be something as simple as that. I've already thrown the kitchen sink at it, what could a fan clutch hurt? Lol. I never really cared for the mechanical fan in reality, might be worth looking into replacing it with an electric fan too.

Yes, the fan is OEM.  The XJ is a 98.  The electric fan sits on the driver side of the radiator and the mechanical fan is on the passenger side of the radiator.  Theres a few inches gap between the two shrouds.  From what I understand, this is how it came from the factory.
98 XJ

Offline wbsjp

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Re: Overheating issues
« Reply #26 on: September 25, 2020, 10:40:24 PM »
Replace the fan clutch with the NAPA unit # I advised  on the first page.Any electric fan set uneven the triple  fans by(IIRC) Griffin did not work as well as the stock set -up with the  HD clutch.
Wayne
  AARP,NAXJA,NRA Endowment member
"the cost of Freedom isn,t Free"

Offline R3

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Re: Overheating issues
« Reply #27 on: October 06, 2020, 08:00:09 AM »
Wondering  if the overheating issues have been tamed or  is it just because it got cooler? :?
Cheers

17 JKURR Daily/rock crawler/overland
2013 Victory XCT hot rod.

Offline XJBayne

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Re: Overheating issues
« Reply #28 on: October 06, 2020, 08:10:14 PM »
Wondering  if the overheating issues have been tamed or  is it just because it got cooler? :?
Haha.  XJ has just been at my mechanic.  He said it passed the cylinder leak down test with flying colors.  Gonna check into the thermostat and make sure everything is working properly there.  I mentioned the fan clutch to him as well and he’s gonna check that out too.
98 XJ

Offline mopar31898

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Re: Overheating issues
« Reply #29 on: October 06, 2020, 09:35:24 PM »
I apologize if this question has been answered but is the engine stock?  Any mids that could be causing this?

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