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Unread 01-21-2014, 02:38 PM   #1
Digger838
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I looked at most of the top of the search list for oil pressure issues, my 2000 tj 4.0 with 134000 miles has fluctuating oil pressure when at idle it drops to 0 and runs normal at speed, also it has a coolant smell too it was wondering what could be the ? Also my heat isn't really "HOT" like I think it should be. So I'm now replacing my thermostat even though the temp gage is reading around 195 where it should I'm now thinking it could be the water pump that might be the next thing I replace, this is going to be my DD so when I get this figured out I will be driving it regularly about 50 miles per day


Last edited by Digger838; 01-21-2014 at 03:08 PM..
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Unread 01-21-2014, 03:24 PM   #2
Zombi
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If you're smelling coolant, your system is likely leaking somewhere.
Check out your passenger side foot well for a strong coolant smell.
If it concentrates there, you likely have a leaky heater core.

As far as the oil pressure goes, have you confirmed that:
1. you have enough oil in the system and
2. your gauge is actually reading correctly?
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Unread 01-21-2014, 04:04 PM   #3
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Sounds like a cracked head or blown head gasket. Pull the oil cap and look inside with a flashlight between cylinder 3 and 4.
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Unread 01-21-2014, 04:22 PM   #4
Digger838
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Ok here is more info. The coolant smell is under the hood not in the cab, the radiator is steaming when I get done with my 7 mile loop around town, not good heat in the cab( medium warm like breath ) oil pressure is good when I start good when I'm driving till I come to a stop then drops to nothing, the top radiator hose is hot the bottom hose is stone cold but heater core hoses are both hot.

Just replaced the thermostat, fresh oil change, fresh coolant

Hope this helps my after said the water pump isn't working, something about the impeller not spinning with something, it's a reman water pump the PO had put on a few months before he parked it, so it has been sitting for a few months.
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Unread 02-19-2014, 11:54 AM   #5
Digger838
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Ok so I did more work on the jeep, new radiator,water pump, T-stat, all fresh coolant, still have oil pressure drop when it's up to temp. When I start it cold the oil pressure is around 40 when it's hot and I'm goin down the road at 55 around 1900rpm it rides around 25-30 when I stop it bottoms to 0 or close to it, should I change the oil pressure sensor? I picked up a mechanical oil pressure gauge but have yet to install it I would like to have both the electric pressure sensor and mechanical gauge, anyone know what size pipe and couplings and thread size I need?? Also do I need to prime the mechanical gauge line with oil?

Thank you

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Unread 02-19-2014, 12:06 PM   #6
96zjlaredo
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No, you don't need to prime it. If you put the mechanical gauge in, just remove the oil sending unit on the side of the block and screw in the new adapter. Be sure to use some Teflon tape on the threads. Also you should buy the COPPER hose kit rather then use that cheap plastic. If if breaks your cab will be nothing but oil. If you want to replace just the factory sending unit, there about $30.00.
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Unread 02-19-2014, 12:14 PM   #7
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Quote:
Originally Posted by Digger838 View Post
Be looked at most of the top of the search list for oil pressure issues, my 2000 tj 4.0 with 134000 miles has fluctuating oil pressure when at idle it drops to 0 and runs normal at speed, also it has a coolant smell too it was wondering what could be the ? Also my heat isn't really "HOT" like I think it should be.

So I'm now replacing my thermostat even though the temp gage is reading around 195 where it should I'm now thinking it could be the water pump that might be the next thing I replace, this is going to be my DD so when I get this figured out I will be driving it regularly about 50 miles per day
Your oil pressure sending unit needs to be replaced.


As far as heat, is both the heater core hoses hot to the touch when the engine is all warmed up? It's possible your heater core needs to be flushed out.
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Unread 02-20-2014, 05:19 AM   #8
Digger838
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Quote:
Originally Posted by JBTJ
Your oil pressure sending unit needs to be replaced. As far as heat, is both the heater core hoses hot to the touch when the engine is all warmed up? It's possible your heater core needs to be flushed out.
Ok so I forgot to put some info in
When I did the radiator and all that I tried to flush the heater core ( let it set with purple power in it for about 15min) then flushed with water and blew it out with the air compressor had some muddy colored water come out and kept running water threw till it came out clear.

I think it might still be plugged though I will try to thaw out the garden hose and let hot water run threw it for a few min when I get the chance.

As for the oil pressure I'm wanting to use both the OE sending unit and the mechanical gauge does anyone know the connector size or how long the T fitting should be to run both of them?

Thank you

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Unread 02-20-2014, 06:36 AM   #9
JBTJ
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Quote:
Originally Posted by Digger838 View Post
Ok so I forgot to put some info in
When I did the radiator and all that I tried to flush the heater core ( let it set with purple power in it for about 15min) then flushed with water and blew it out with the air compressor had some muddy colored water come out and kept running water threw till it came out clear.

I think it might still be plugged though I will try to thaw out the garden hose and let hot water run threw it for a few min when I get the chance.

As for the oil pressure I'm wanting to use both the OE sending unit and the mechanical gauge does anyone know the connector size or how long the T fitting should be to run both of them?

Thank you

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The heater core must be in near perfect condition in order to get hot air. The more crap that's in there the less heat you will have. A good way to tell is feeling the two hoses going to the core. If one is hotter than the other, it's still plugged up.

9.9 times out of 10 the oil sending unit goes bad. It's a very common problem. I'd just replace it with an OEM one and be done with it. If that doesn't fix the problem then you can worry about how to hook up a mechanical gauge. IMO
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Unread 02-20-2014, 07:49 AM   #10
Digger838
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Quote:
Originally Posted by JBTJ
The heater core must be in near perfect condition in order to get hot air. The more crap that's in there the less heat you will have. A good way to tell is feeling the two hoses going to the core. If one is hotter than the other, it's still plugged up. 9.9 times out of 10 the oil sending unit goes bad. It's a very common problem. I'd just replace it with an OEM one and be done with it. If that doesn't fix the problem then you can worry about how to hook up a mechanical gauge. IMO
Ok haha forgot more info on the heater core, when it's up to temp the hose on top is hot where as the hose on the bottom is hot but not as hot as the top hose.

But I'm gana get a hold of my buddy who works at a jeep dealership and see what he can get me for a oil pressure sending unit and a heater core all OEM at that
Thanks for all the help I'll try to keep updating as soon as I can

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Unread 02-20-2014, 07:57 AM   #11
JBTJ
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Originally Posted by Digger838 View Post
Ok haha forgot more info on the heater core, when it's up to temp the hose on top is hot where as the hose on the bottom is hot but not as hot as the top hose.

But I'm gana get a hold of my buddy who works at a jeep dealership and see what he can get me for a oil pressure sending unit and a heater core all OEM at that
Thanks for all the help I'll try to keep updating as soon as I can

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Try disconnecting both heater core hoses, not at the core but the other end. Blow out with air and tie them up so they are higher than the inlet. Then fill the heater core up with vinegar and allow to sit for a few hours, and then flush out with water. The vinegar will eat up all the crud in the core. If this does not help the core needs to be replaced.
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Unread 02-20-2014, 08:07 AM   #12
Digger838
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Quote:
Originally Posted by JBTJ
Try disconnecting both heater core hoses, not at the core but the other end. Blow out with air and tie them up so they are higher than the inlet. Then fill the heater core up with vinegar and allow to sit for a few hours, and then flush out with water. The vinegar will eat up all the crud in the core. If this does not help the core needs to be replaced.
I did something like that I used purple power and let it set for like 15 ish minuets took the air gun to it and then flushed it with water till it came out clear and still no heat, just for sh/ts and giggles what does everyone's hot air run at for a temperature?

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Unread 02-20-2014, 11:09 AM   #13
JBTJ
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Quote:
Originally Posted by Digger838 View Post
I did something like that I used purple power and let it set for like 15 ish minuets took the air gun to it and then flushed it with water till it came out clear and still no heat, just for sh/ts and giggles what does everyone's hot air run at for a temperature?

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Not sure what that is or if it works as well as vinegar for this application. May want to try it as it's cheaper than installing a new heater core.
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Unread 02-20-2014, 02:25 PM   #14
Digger838
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I think I'm gana try pulling the heater core soaking it in purple power( like CLR but is ok to use with aluminum) then rigorously flushing it with a hose or something. And just bypassing the heater core for a few days good thing this isn't my DD lol

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Unread 02-20-2014, 03:50 PM   #15
JBTJ
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Originally Posted by Digger838 View Post
I think I'm gana try pulling the heater core soaking it in purple power( like CLR but is ok to use with aluminum) then rigorously flushing it with a hose or something. And just bypassing the heater core for a few days good thing this isn't my DD lol

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That will be a PITA. I'm hoping you will not have to do that.
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