89 YJ Oil Pressure and Engine Temp Problems - Jeep Wrangler Forum
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Old 03-05-2010, 01:42 PM   #1
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89 YJ Oil Pressure and Engine Temp Problems

Hey all. I've got a few problems with the engine temp and the oil pressure. When first turning it on, cold, the oil pressure is right at about 50. As I drive it and the car warms up, the oil pressure drops down real low to half of the 40 mark. I don't really notice any performance issues but sometimes I think I can trick myself into believing its losing power. I checked the oil levels and it looks good. I do have a small oil leak coming from the rear main seal, i think, which i plan on repairing soon.

My second problem is the engine temp. I let it warm up before I drive it to about 150║ and as I'm driving it warms up as usual to 210║, after about 5 or 10 minutes of driving it at 210, it starts to overheat over 210. The temperature will come back down to 210 after a bit but it seems to fluctuate from 190 to 210 to 250. It kind of scares me driving it like that getting that hot.

When I turn her off, I sit in the seat for about 10 minutes and then turn her back on to the acc. position so i can see the gauges and it says some crazy number like 250. If i crank her on, the temp will go back down to 210, I'm guessing cause the fan is on and it cools it down.

I don't know why this is happening. I appreciate everyone's help!

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Old 03-05-2010, 02:29 PM   #2
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My temp gauge was also acting crazy for quite some time.

My radiator blew one day, so I went ahead and did the water pump, thermostat and temp sending unit. Temp gauge works fine now. Not sure if this is your problem or not. I'd get a second opinion before switching the water pump as it was a bit involved for a novice wrench like me, but I did it. The thermostat's easy enough to do. If you're not leaking or anything, start with the thermostat maybe? Or temp sending unit?

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Old 03-05-2010, 03:57 PM   #3
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my temp gauge was freaking out and then died on my 87 so i switched out the thermostat and put in a new temp gauge and havent had a problem since
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Old 03-05-2010, 05:11 PM   #4
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The good news is that you most likely have a minor issue with the temp. problem because if it really reached 250 a lot you would cause engine damage after awhile.
clean and make sure your temp sensor connection , make sure your fan/ pump belt is tight and not slipping replace or tighten if it is . drive it after do these to see if it fixed the problem . if not then try flushing out radiator and replace thermostat and rad cap drive it and test it. if this did not work replace temp. sensor and test again . if still doing it time for a water pump ( not to hard to replace ) .
If you have the money do all of them at one time and be done with it.
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Old 03-05-2010, 05:12 PM   #5
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On my 89 I replaced the oil sender switch, which helped, but the gauge is more of an indicator. Depending on the temp. of the oil, the pressure runs about 60 cold and between 40-60 lbs. hot. My engine runs great and there are no problems other than the same minor oil leak. It will read better with the new switch which I believe you can get for approx. $30. It seems like your thermostat is on the way out. You should replace it right away. If your radiator is over 10 years old you should probably think about replacing that too. If your water pump isn't leaking or making a lot of bearing noise it's probably o'k.
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Old 03-05-2010, 11:32 PM   #6
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Your oil pressure minimum at idle is 13 PSI and at 1600 rpms or more should be between 37 to 75 PSI. I would opt for the sending unit (sensor) and see what you get.
Does however sound like your thermostat is starting to go. Before you replace it flush the system and then install the thermostat and check the flow through the radiator.
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Old 06-06-2011, 11:18 PM   #7
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yj 2.5l Temp Sending unit

I recently had similar overheating problems with my 89 2.5l. I replaced the theromstat ($5) and the waterpump ($30) and did a massive flush of the whole system. it was nasty. my water temp gauge went out right before all my other coolant issues started, i suppose i will need to change the temp sending unit. Does anyone have a pic of this? I keep reading in threads its near the manifold - firewall driverside and has one wire coming out of it. I have two - two wire units, one on top and one on the side. Any more location details would help. thanks.
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Old 07-29-2013, 01:48 AM   #8
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I have a 1989 Wrangler. My entire gauge cluster was reading incorrectly, so after some research, I found this link ..

Repair w/pix - Stock Gauge Cluster how-to - JeepForum.com

Did this repair and I now have accurate reading across the board. Before this job, I thought I was running hot on engine temp, and I thought I had way to high oil pressure .. and my gas reading was never accurate ...
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Old 07-29-2013, 08:07 AM   #9
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Quote:
Originally Posted by Shadowpath View Post
I have a 1989 Wrangler. My entire gauge cluster was reading incorrectly, so after some research, I found this link ..

Repair w/pix - Stock Gauge Cluster how-to - JeepForum.com

Did this repair and I now have accurate reading across the board. Before this job, I thought I was running hot on engine temp, and I thought I had way to high oil pressure .. and my gas reading was never accurate ...
This thread should be considered the Holy Grail for all YJ owners. I owe '1989 YJ Wrangler' big time for first writing this important thread. Not only is this a fantastic how-to guide but his comment that "In my jeep EVERYTHING works. Period" has been my guiding philosophy since I first read it.

I read around this Forum other owners bitching that jeep gauges are garbage or have always been notoriously inaccurate which is just NOT true. It's just that this circut board which has been out in the elements (for 26 years in my case) that usually needs a little love. Whenever I buy my next YJ project, after I change the oil and fluids, I'm doing this fix before anything. It's the circut board not the gauges. Trust me....clean it or replace it if necessary and I'm betting you will be pleased with the result.

This is the first jeep I have ever owned and here is a pic of my dash warmed up and idling at 800 RPM with everything working perfectly. Even my 26 year old clock and all thanks go to the '1989 YJ Wrangler' thread. I can now say....."In my jeep EVERYTHING works. Period". Well, almost but I'm determined to get there.
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Old 07-29-2013, 08:15 AM   #10
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Forgot. I also suggest your changing he thermostat using a paper gasket not that blue RTV silicon. It's an inexpensive and easy fix which could be the solution.

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