99Justin4.0

I just bought a 99 Grand Cherokee 4.0L 200,250 miles.

I went with the 4.0 because I hear they're pretty bullet proof. I'm not too concerned, but here's whats going on.

It ticks really loud. My first guess is a manifold leak, or a lifter.

The oil pressure is all over the place. From pinned to None at all.

The lady said it's always ticked since she bought it. And her "mechanic dad" said the oil pressure is probably a faulty pressure sender.

It runs perfect. The oil is clean. Temp is constant 210 (right in the center). Has perfect power. Just ticks really loud, and that gauge is all over the place.

I should also mention that this is a 100% unmolested Jeep.

Any suggestions would be greatly appreciated. I have a lot of mechanical knowledge, just new to Jeep.

Thanks a lot!

get3coffinsready

Oil pressure will change depending on temperature, engine speed, idling or even if you are on an incline. If it is within acceptable tolerances, i would not worry about it. (i think 30-50, don't quote me on that).

The ticking could be a couple of things, the flex plate is known to crack or come loose and make that noise. A worn out timing chain can also make alot of noise.
Its best to pinpoint where the noise is coming from (front, rear, top, bottom)

Cleanup the oil on the bottom of the pan and engine area, run it and see if you can pin point the area the leak is coming from. Overtime the oil filter adapter, valve cover, oil pan gasket and rear main seal can all leak oil. Also check the drain plug as the rubber could be worn out or the wrong bolt could have been used.

99Justin4.0

It doesn't leak oil. The oil pressure gauge just reads pinned 80 or flat 0. Not too much in between. Which leads me to believe it's the sender switch.

I'll have to research the flex plate, not familiar with that.

As far as timing chain, is that a tough job?

get3coffinsready

I have not had to do mine yet, but i have seen youtube videos of people doing without needing to remove the engine. You will have to remove the fans, radiator, pulleys belt and anything else that is in the way so it is doable but it will not be pleasant.

99Justin4.0

Oh man, that's gravy... Try a Porsche 944S 16V Timing Belt...

I think I'm really going to like my Jeep!

Still like to know some opinions on that pressure gauge though.

get3coffinsready

i will yield to other people on the forum about the sender, i found some one on youtube describing and repairing a very similar situation.

99Justin4.0

Thanks for that vid. I'll let you know if it works tomorrow!

Low pressure scares me. The tick, not so scary. So first things first.

bryanintowson

My oil pressure sensor recently went bad while I was driving. All of a sudden the oil pressure spiked and the gauge pinned then went down to zero. Then back and forth a bunch until reading 0 and spiking to 20 when I accelerated.

Drove straight to NAPA, got a new one and installed it about half an hour later. The sensor has a diaphragm in it and that had completely failed and oil was literally squirting out of the connector.

All fixed.

storm101

Replace the sender- they Usually fail either 100% pegged high or low, so a combo of both would also indicate this--- if you had 0 oil pressure you'd know it and I'm sure you wouldn't be going anywhere for long lol.

As far as the tick goes, 4.0's have a tick to them... They're known to be noisy, check the exhaust manifold for cracks - near the collector where all the cylinders meet into one, that's common and also makes noise typically described as a tick.

Take a screwdriver as well and hold the handle to your ear and poke around, if you can pick up where the tick is "loudest" through the handle, that's a good area to investigate in.

99Justin4.0

Thanks for all the input. I'm getting a sender today. Only question I kinda have if anyone see's this before I get to it: Once all the oil settles back down, it should be below the sender right? Like I don't want to pull this thing out and have oil shooting out.

No drainage required right?

And thanks storm101. I have one of the doctor's stethoscope
style noise stick things. I'll use that.

My mom wont shut up about me "getting ripped off" because the thing ticks. I really just want to shut her up.

As far as I'm concerned I have a perfect unmolested WJ foundation. I used to work on Water-cooled VW and Porsche, when something went wrong then it was bad. And very expensive. That's the whole reason I came over here to the Jeep world.

EZEARL

Nothing will come out.

Don't know if it applies to the GC but make sure you get the sender for gauges and not idiot lights.

As far as the ticking goes what does it look like under the valve cover? Could just be sludged up.

extrashaky

The senders usually fail low. A meter pegged to 80 psi is usually a short or bad ground. You could have both. Check the wiring going into the sender connector to see if oil contamination has rotted the insulation there so that the wires are shorting.

My 2000 XJ had a bad sender that leaked oil through the connector, which in turn ate the insulation right off the wires in the wiring harness. I realized what had happened when I touched the wires while the truck was running and had the engine instantly die. I had to cut a few inches into the wire loom to get to some good wire to patch to.

I was going to suggest you get a stethoscope and determine exactly where that tick is coming from, but are you sure it's coming from the engine? If it's not the engine, you may need to get a length of tubing and use that to find your noise. Put one end up to your ear and move the other around the engine bay until you find the source.

In addition to the other possibilities already mentioned, the XJs have a purge solenoid in the evaporative emissions system that can click like a ****, especially if there's a vacuum leak or the thing has been knocked off its little mount. You may have one also. If so, check to see if that's the source of the tick. If it is, it's not a big deal.

Dumajones

Just to add to this post ^^^^^^

This is what the Evap purge solenoid sounds like clicking. It can sometimes be confused for a motor tic.

99Justin4.0

Sound is loudest under the jeep. Hope it's not the flex plate...

99Justin4.0

Flexplate, Timing Chain, Piston Skirt, Piston Slap, Cracked Head, Stuck Lifter, Worn Cam Lobe, Loose Rockers, Exhaust Leak, Rod Bearing, It just sounds that way and it's fine, AAAAHHHHHHH!!!!!

It sounds like a diesel and I'm going crazy.

I haven't even worked on it actually. No time. But these youtube videos are driving me insane.

I had this purchase very well planned out. I figured I could roll the dice on the engine noise because everything else is perfect.

I had a budget, I spent about 5/9th's of it on the Jeep itself. The other 4/9th's are for making it purr nicely.

It's american, parts are everywhere and dirt cheap, and it's gravy compared to german cars to work on. This should be a good plan. Lose the tick. Everything will be okay.

Just a neurotic rant. Too much internet diagnostic research.

Thanks again for the input new Jeep friends. I'll actually get time to work on her tomorrow and give a better update.