Oil pressure shananigans
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Junior Member
Joined: Jul 2010
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From: Delaware
Year: 1997
Model: Grand Cherokee
Engine: 5.2l
Oil pressure shananigans
I have been having trouble with oil pressure with a `97 Grand Cherokee with a V8 engine I recently bought. When I would first start the engine the pressure would be normal, then after a while the pressure would go down to zero, according to the gauge. I replaced the oil pump, but now I get no reading on the gauge. The engine temp is stable, & the oil pan feels hot(normal hot). Could it be an issue with the sending unit?? If so, where does one find this device on the engine??
Last edited by Ja-Seen; Jul 21, 2010 at 07:14 PM.
Thread Starter
Junior Member
Joined: Jul 2010
Posts: 30
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From: Delaware
Year: 1997
Model: Grand Cherokee
Engine: 5.2l
Thread Starter
Junior Member
Joined: Jul 2010
Posts: 30
Likes: 0
From: Delaware
Year: 1997
Model: Grand Cherokee
Engine: 5.2l
I wasn't able to find a mechanical gauge yet, so I went ahead & replaced the sending unit anyway, but still no dice. The gauge still reads zero. When i started her up to test it, I started getting some valve tapping. I haven't moved her at all. My brother's friend is having the same problem with valve tapping, but not with oil pressure. I plan to chat with her tomorrow. Anyway, does anyone have any thoughts/suggestions???
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Joined: Jan 2010
Posts: 704
Likes: 1
From: Mt. Iron, MN
Year: 96 Limited ZJ
Model: Grand Cherokee
Engine: 5.2 w/mods
I have been having trouble with oil pressure with a `97 Grand Cherokee with a V8 engine I recently bought. When I would first start the engine the pressure would be normal, then after a while the pressure would go down to zero, according to the gauge. I replaced the oil pump, but now I get no reading on the gauge. The engine temp is stable, & the oil pan feels hot(normal hot). Could it be an issue with the sending unit?? If so, where does one find this device on the engine??
3 things that can cause this.
- Best case... Engine is just getting tooo hot and oil thins out, so the pump can't pick it up fast enough... the faster the engine spins, the faster it can pump. (this is the least of the three that it probably is... cause even at 100 rpms, the pump should be spinning fast enough to make good pressure...) Think about it. You can use a cordless drive with a long hex extension and prime your engine to make at least 10 - 20psi.
- Next thing it could be.... A bad sending unit... so take yours off and hook up a mechanical gauge to it. FYI: The sending unit has to read a min of 11psi before it will start to register a pressure reading. (you already replaced your sender )
- Third thing is the worst case... and maybe the probable case. How many miles do you have on her? A lot or not that many?.... really doesn't matter, cause it just takes one bad thing in there to make this happen. The babbit materials on your rod and main bearings are very soft. It takes just a slight NICK in them from a metal shaving or detonation on a piston to disturb a rod bearing and you start like that.... Your bearings start to wear prematurely, opening the clearance up a ten thousand of an inch. Once this happens, you will lose oil pressure at lower RPMs and when NO pressure happens, your engine is already HOT and now you have no oil lubricating the bearings while it is spinning a min of 1000 revolutions per minutes.... IMAGINE the heat... Metal on Metal, then the light turns green and you gun it to 3000rpms... Scorching your crank and rods.
Last edited by country_boy454; Jul 22, 2010 at 09:30 PM.
Thread Starter
Junior Member
Joined: Jul 2010
Posts: 30
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From: Delaware
Year: 1997
Model: Grand Cherokee
Engine: 5.2l
3 things that can cause this.Third thing is the worst case... and maybe the probable case. How many miles do you have on her? A lot or not that many?.... really doesn't matter, cause it just takes one bad thing in there to make this happen. The babbit materials on your rod and main bearings are very soft. It takes just a slight NICK in them from a metal shaving or detonation on a piston to disturb a rod bearing and you start like that.... Your bearings start to wear prematurely, opening the clearance up a ten thousand of an inch. Once this happens, you will lose oil pressure at lower RPMs and when NO pressure happens, your engine is already HOT and now you have no oil lubricating the bearings while it is spinning a min of 1000 revolutions per minutes.... IMAGINE the heat... Metal on Metal, then the light turns green and you gun it to 3000rpms... Scorching your crank and rods.
Last edited by Ja-Seen; Jul 22, 2010 at 10:40 PM.
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Joined: Jul 2010
Posts: 8
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From: Allen County, KY
Year: 1996
Model: Grand Cherokee
Engine: 4.0
Ja, I also bought a laredo for 900, I just think the pump went out, but I did that (smoked the bearings). Now I've got sa 4.0 in it not the v-8, but there is a place in my town called Southern Kentucky Engines. I got the rebuilt long block for $900+$200 for 100,000 mile warranty. If this is your problem, it won't take long.
Thread Starter
Junior Member
Joined: Jul 2010
Posts: 30
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From: Delaware
Year: 1997
Model: Grand Cherokee
Engine: 5.2l
Ja, I also bought a laredo for 900, I just think the pump went out, but I did that (smoked the bearings). Now I've got sa 4.0 in it not the v-8, but there is a place in my town called Southern Kentucky Engines. I got the rebuilt long block for $900+$200 for 100,000 mile warranty. If this is your problem, it won't take long.
Last edited by Ja-Seen; Jul 22, 2010 at 11:56 PM.
Thread Starter
Junior Member
Joined: Jul 2010
Posts: 30
Likes: 0
From: Delaware
Year: 1997
Model: Grand Cherokee
Engine: 5.2l
Question: Is there a proper way to prime an Oil pump? I saw something about vasoline. How does that work?? Like I said, I'm broke & digging for short term solution until I can sort this out.
Thread Starter
Junior Member
Joined: Jul 2010
Posts: 30
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From: Delaware
Year: 1997
Model: Grand Cherokee
Engine: 5.2l
OMG! Just pulled off the valve cover, & there is some super thick, crusty sludge.Looks as though it hasn't had a good oil change in several years.
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