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Generation 2 Pajero NH - NL Models 1991 - 2000

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  #21  
Old 1 Week Ago
erad erad is offline
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Quote:
Originally Posted by stumagoo View Post
the bypass is for the cooler and I am unsure if it just returns to the sump or not but I have good pressure when mine is noisey
My NL used to clatter like mad after it had dragged my caravan up a long hill and the engine got very warm. I could hear the oil cooled cutting in then, and it sounded like a pressure relief valve, although obviously it was temperature which was triggering a bypass. All oil pumps have a bypass to limit pressures in the system, otherwise you tend to blow seals etc.
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  #22  
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tomwithannl tomwithannl is offline
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As others have said that noise is not too unusual but get a good oil pressure gauge to check what yours is actually doing, the factory one is really just for show.
I would be more worried about your charging voltage going by your second video.

Tom
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  #23  
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disco stu disco stu is offline
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A thought that may be relevant

When I bought this car, it had that "diesel" type sound underneath, and was told to check the exhaust manifolds for cracks. They were both cracked as expected.

I sealed these cracks up with the 2 part stuff designed for exhaust manifolds, not being keen on causing further issues through welding. When I first got the new engine going I don't recall this sound being present, but it's there now. I'm pondering the possibility that the putty has failed causing the noise.

Just throwing the idea of there that this is the cause of your noise also
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  #24  
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brw0513 brw0513 is offline
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Originally Posted by erad View Post
There is a pressure relief valve in the oil pump. I had thought that this may be the culprit, but I would expect that it would be operating more when the oil was cold and thick, not when the oil had warmed up. Certainly, on my old Triumph 2000, I could hear the pressure relief valve operating when the engine was cold. Even so, maybe the pressure relief valve is open all the time when the oil is cold, and when the engine warms up, maybe the valve is starting to close. This could be because the spring in the relief valve is weak or broken (I always think the worst in any situations like this). Any oil dumped at this point would then be returned to the sump. As for linking the frequency of the clicking to the engine speed, you would have to know what gearing is between the crankshaft and the oil pump before you could specifically say what the problem (if any) is.

For what it is worth, my Max Elery W/S manual talks about the oil pump. In the dismantle section, they tell you to remove the timing belt, the sprocket and key, release the oil pan assembly and then undo the oil pump retaining bolts and release the oil pump from the engine block. This sounds like a LOT of work. Then they tell you to remove the cover plate , withdraw the rotors from the pump and then release the relief valve circlips from the rear housing body and withdraw the piston. They then tell you to inspect the piston surfaces for smoothness of the surfaces where they mate to other surfaces. A LOT of work.

For starters, fit a known pressure gauge and see what the oil pressure actually is. If you can see the gauge fluctuating, you may be able to link the noise with change in pressure. If the pressures are still good, I probably would not worry too much about it because the engine will still be receiving oil to all areas which need it. The manual states the oil pressure should be 29 kPa (4.2 psi) at idle, and 294 -686 kPa (43 - 100 psi) at 3500 R/min. I would assume then that the pressure relief valve would be opening at 686 kPa (100 psi). These figures are for the petrol engine, which I assume that you have (if you had a diesel, you wouldn't hear a damned thing down there). If you get oil pressures around the 300 kPa mark, I would be happy with that and close my ears to the noise. The oil pump is solely to distribute oil around the engine, not to provide a load bearing film on the bearings etc. The bearings in turn drag what oil they need into the ever decreasing gap between the bearing shell and the shaft journal, and the oil then builds up very high pressures to maintain separation between the rubbing surfaces. The oil pump could never give enough pressure to do this function, and its use is solely to ensure that there is adequate oil present at the rubbing surfaces so that the natural oil wedge can be built up between those surfaces.
Thanks erad for the detailed reply. I would like to track down a Max Elery manual for the library. And thanks to stumagoo too for your reply.

Yes erad - it is a petrol engine and I agree about the oil pressure test. I have now purchased a tester and will use it on the weekend.

It is a lot of work to get to the oil pump. I fitted a timing belt kit and water pump less than 20,000km ago so have some experience with related work and length of time it will take. The skinned knuckles, sore neck and back, frustration with lack of flexibility and strength with age, swearing and loathing at the lack of design for maintenance effort that Mr Mitsubishi offered us.

But I reckon I'll be disappointed on my death bed if I don't get to the bottom of this ticking. And of course this has happened at the time I'm thinking of selling the NL. I would be compelled to tell a new owner about the noise and suspect that will cost me a sale for a good price.

The audio signature is interesting. There is a definite pattern to the tick and I will be able to calculate the period of the tick.

The inner rotor of the oil pump has 8 lobes and the outer rotor has 9 reliefs (apparently). My latest theory is the one of the lobes and one of the recesses is damaged and the tick occurs when these two items meet.

With my lathe I've turned up a threaded plug to replace the oil bypass valve. I should be able to rule that out. I'll also check the oil cooler and the supply and return line to confirm there is no blockage.

The pressure relief valve is worth a look too. I can see it in my manual's exploded diagram. And I can see it on a pic of a new pump. But I must need a mirror to see it in real life. No doubt Mr Mitsubishi wants that hard to access by lack of forethought too.

I'll post results if I discover anything.
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  #25  
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Scooby Scooby is offline
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Have you cut an oil filter open yet to see if there is any metal being generated?
Use a pliers or side cutters and open the filter at the top crimp.
You could use a hacksaw and cut the bottom off where the metal wont go on the filter and contaminate it, but not recommended.
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  #26  
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erad erad is offline
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Now Scooby has raised an interesting point... I believe that the oil filter has a bypass valve built in to allow for when the filter is blocked. Maybe the bypass valve is clacking away? How old is the filter? Have you recently replaced the filter? It may be worth throwing another filter at it and seeing of it goes away before getting deep into the engine
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brw0513 brw0513 is offline
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Hi guys. Thanks for the suggestion. I have tried a new filter. No change I'm afraid.
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  #28  
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brw0513 brw0513 is offline
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Quote:
Originally Posted by tomwithannl View Post

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I would be more worried about your charging voltage going by your second video.

Tom
Sorry Tom - I missed this post.

What is it that you see?

The charging circuit is putting around 14V to the battery when charging. I consider that normal.
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  #29  
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brw0513 brw0513 is offline
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I did some testing earlier today with a Super Cheap Auto oil pressure tester. I've never really trusted any SCA tool, but "name brand" testers are many hundreds of dollars.

The results are shown in the graph below. All tests were using the Nulon 10w-40 oil.

Test #1 was after refilling the engine with oil. I had drained it to check the oil coiler and supply and return lines to verify they weren't blocked. The cooler bypass valve was removed and replaced with an M24 x 1.5 plug. Interesting the oil pressure hung up high for a while. But this was a completely cold engine and the oil would have taken some time to get distributed through the cooler.

Test #2 was with the bypass plug still installed. It was around 2 hours after the first test.

Test #3 was with the cooler bypass valve re-fitted and around 1 hour after the previous test. The ticking noise is still present, so it isn't the bypass valve.

When the engine was warmed up and running at 3500rpm, the oil pressure was 82 PSI.

My Haynes manual (and erad's Max Ellery manual?) states oil pressure at idle should be 29kPa (only 4.2 PSI !) and 294 to 686kPa (43 to 100 PSI) at 3500rpm.

My MM Montero manual, nominates an oil pressure of 80 kPa (11.4 PSI) or more at idle speed.

During testing the oil pressure gauge needle was very stable, no flickering or pulsing.

The developed oil pressure at 3500rpm seems good. At idle, the indicated pressure seems to be a little high.

I'm going to have a sleep on it tonight. The testing has proved the bypass valve is not the culprit. Shame because it's about the easiest thing to get to on the engine! To go any further is some serious effort to remove the front diff to remove the sump

I'm suspecting now it is the oil pump pressure relief valve. Conjecture here, but could it be completely unseated when the engine is cold and then be bouncing when the engine warm?
Attached Images
File Type: jpg Pressure Tests.jpg (42.4 KB, 10 views)
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  #30  
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erad erad is offline
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Recapping on the whole situation - have you owned the car for a long time or just acquired it? If the latter, its history is unknown. What was the engine speed when you did these tests? Readings at idle and 3500 R/min would be helpful. Whatever, I think the oil pressures are OK. The ticking didn't seem too bad to me. It could still be the oil pressure relief valve unloading - you are measuring the oil pressure after the pressure relief valve and there is probably no way to measure it before the unloading valve. The fact that you have about 30 psi after 20 minutes seems to indicate that the rest of the engine is in good condition. if you have worn bearings you would be getting much lower pressures.

Since you have thicker oil in the the beast before, maybe you should put some flushing agent through the sump and discard the fresh new oil. If you still have the old oil, I would carefully drain the new stuff, refill with the old oil and then add a flushing agent to it and warm the engine well and then drain it again. Then put the new old back again (assuming it hasn't been contaminated with dirt). If the pressure relief valve on the pump is sticking, this may help to release it.
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