Video here >> http://www.youtube.com/watch?v=NT6E09q-lQ8

I had this 98 Mitsubishi Montero Sport LS 3.0L V6 for a month or so and noticed a slight tap/tick noise. I checked the oil pressure and it would dip low probably below 10psi.. you'll see what I mean if you check the video. I figured the oil was just bad so I changed it out as well as a new filter and I was back on the road and all was good. That is until after I drove about 5-600 miles and then it started again! Slight at first, then louder and louder. My best guess is a cracked head gasket leaking antifreeze into the oil causing a bad bearing? Or a really crappy oil pump? Has anyone had a similar problem or can offer some insight?

 

There is an easy way to check the head gasket issue. Simply get a compression tester.

Either that or the old school ways. Check under the oil cap for a white goop, and watch for bubbles coming from the radiator.

Personally that sounds to me like a stuck lifter. I bet this thing was majorly starved of oil at some point.

 

Sounds like rod knock but its hard to tell from the video. What oil did you put back in it?

 

Like Sebba said, if it was a cracked head or leaking gasket there would be coolant in the oil and/or tan goop inside the oil filler cap.

That type of problem is rare on these engines but what is very common is what what Sebba also said - stuck lifter or, in the case of Mitsu terminology, Valve Lash Adjuster or VLA. I had the same thing twice when I let the oil level get very low - something your PO probably did.

It sounds exactly like a bottom end knock - very scary but that also is something that almost never happens. Try this fix - which is also advised in the official factory service manual. I'd bet it fixes your noise problem - at least it worked both times for me.

http://www.4x4wire.com/mitsubishi/te.../lifter_noise/

Ron

 

If the problem comes and goes, I doubt if it's rod knock or anything like that. Look at the common problems in these engines first, namely lifters and the timing belt tensioner. Do a compression test but it's not likely to be the head gasket. After you've eliminated that and the VLA fix jrmdir posted above, I would check into the timing belt tensioner. If it's time for a timing belt, just replace the tensioner with a new one (along with the belt and water pump) and I'll bet the noise goes away.