4.0 HIGH OIL PRESSURE PROBLEM

WHILE WHEELING IN NJ RECENTLY I NOTICED SOMETHING STRANGE WITH THE OIL PRESSURE IN MY 98 TJ 4.0   I'VE NEVER HAD A PROBLEM BEFORE, I DON'T BEAT IT, AND I ALWAYS CHECK MY FLUIDS BEFORE WHEELING.  AFTER A COUPLE HOURS IN THE WOODS I NOTICED THE OIL PRESURE WOULD DROP OFF AT IDLE.  I DIDN'T HEAR ANY NOISES, THE BEARINGS WERE QUIET, AND THE PRESURE WAS GOOD JUST OFF IDLE.

BEING SAFE I TRAILERED IT HOME AND IT SAT FOR A COUPLE DAYS.  WHEN I WENT TO DRIVE IT OFF THE TRAILER THE OIL FILTER GASKET BLEW OUT.  IT DID THIS WITHIN SECONDS OF THE ENGINE STARTING.  I THOUGHT "THANK GOD IT HAPPENED ON THE TRAILER AT HOME INSTEAD OF DEEP INTO A TRAIL".   SO I INSTALLED A NEW FILTER AND ADDED OIL TO GET IT OFF THE TRAILER.  AS SOON AS I STARTED THE ENGINE IT BLEW THE NEW FILTER GASKET OUT.  IT WOULD ALSO STALL THE ENGINE AS SOON AS IT BUILT OIL PRESURE.  I'M NOT SURE OF THE PROBLEM I THINK IT'S A STUCK PRESURE REGULATOR IN THE OIL PUMP.

A FRIEND QUESTIONED THE HEAD GASKET.  THIS THING GETS INSTANT HIGH OIL PRESURE.  I DON'T THINK THE HEADGASKET WOULD BLOW A FILTER GASKET.  ANOTHER REASON IS ITS BLOWING THE FILTER GASKET OFF.  THERE REALLY IS NO WAY FOR A BLOWN HEADGASKET TO GET PRESURE INTO THE FILTER.  IF IT WERE A HEAD AGSKET I THINK I WOULD GET OIL IN THE COOLANT FIRST.  

I HAVEN'T PULLED IT APART YET, ANYONE WITH ANY IDEAS???

That's a strange problem that you have. When you first changed the oil filter did you notice if the gasket was on it, sometimes they come off the oil filter and get stuck to the engine block. Two gaskets together would cause a blowout of engine oil. Are you sure you have the right amount of engine oil in it.

That is weird. I have never heard of that problem before. I have a '98 cherokee I would be interested to know what the cause of this problem is if you ever get to the bottom if it.  

I would check what ranger said about seeing if there isn't an extra gasket stuck on there.  You are correct though in the fact that the head gasket wouldn't have anything to do with it.  

I've been in the fast lube buisness for 6 years now and have serviced over a hundred thousand vehicles.

Occasionally I see a problem like yours where the filter gasket blows out or in extreme cases the filter literally grenades. and usually it's one of the following problems.

1.   The filter is plugged.  A leaky head gasket will create sludge which can break loose and plug a oil filter or oil pump by pass. even though a vehicle shows no visible signs of a head gasket leak Its possible that coolant is getting into the oil and creating sludge . send the oil filter that first failed to the manufacturer or a laboratory like Blackstone to be analyzed. Send a oil sample too if possible. This is cheap and worth it because even if the filter or head gasket arent the problem it can give you an idea of what is going on inside your engine. Oil analyzation is a good preventative maintenance tool in that it can spot possible problems before they happen. Go to Blackstones web site they can help.

2. The Pressure releif spring/bypass in the oil pump is stuck. sometimes draining the oil and changing the filter can solve this.

In your case the oil pump is probably at fault.  If you can pull the oil pan without pulling the motor it's a realtively easy fix