Another Low Oil Pressure Query

[skipperpete]

I’ve never been happy about paying Yanmar $200 for a gasket set and getting 2 tubes of 3bond form a gasket and a head gasket.
Is there the vaguest possibility that the squeeze out liquid gasket on the inside of the oil pan has detached and met up with the oil pump suction.
It was mentioned earlier that the oil pan was seen to be clean so that’s very good news regarding bearing wear.
The master oil pressure gauge will contribute a starting point for a diagnosis.
Oh , just to be clear, I’ve never seen a lube oil suction completely blocked by gasket squeeze alone, other stuff and occasionally a few bits of gasket silicone but never the full blockage.

[wingssail]

Originally Posted by kmacdonald

What is bothering me about the rear main oil seal being replaced is why it started leaking. Is the rear main bearing worn?

It is actually a side issue to this problem but your question is valid. I don't know why the rear main oil seal started leaking, maybe 6000+ hours, it was gradual over some years and finally we decided to replace it, big job for us but we did it and there is now no leak. We do not know how to check for rear main bearing wear and did not.

[Scubaseas]

The rear seal was probably leaking because the 27? year old/6500 hours rubber was hard.

The difference between a relief valve and a pressure regulating valve is simply semantics. They do the same thing and work the same way. A piston and a spring to regulate and dump off excess pressure. The purpose of the one in the oil pump is to regulate or dump off pressure after it hits a set amount, probably around 80psi or so. The second regulating or relief valve opens to dump excess pressure to lower the oil pressure to the supply line to the oil cooler and the turbo on "T" models. Look up dual relief VW type 1 engine to get a good idea of how a two valve system works.



My point was and is the issue of reduced flow to the valve train is of more concern than the lowish oil pressure. If the regulating valve in the oil filter housing is getting stuck open this is the same as having excess clearance someplace. The valve is there to regulate the oil pressure to the cooler, not the main oil gallery. Will the oil pressure drop if it's stuck open? Sure because you effectively now have a 10mm hole in your oil gallery.



Is the problem likely a stuck regulating valve in the oil filter housing? I would say yes. But if that doesn't solve the problem of BOTH the oil pressure and the low flow to the rockers my opinion would be you need to find where the excessive clearance problem is. Which unfortunately means pulling the motor. So hopefully the worst case scenario here is the bore is worn on the filter housing and is causing the piston of the regulating valve to get stuck open thereby creating excess clearance and dumping pressure and flow into the oil pan.

[Compass790]

Originally Posted by Scubaseas

The rear seal was probably leaking because the 27? year old/6500 hours rubber was hard.

The difference between a relief valve and a pressure regulating valve is simply semantics. They do the same thing and work the same way. A piston and a spring to regulate and dump off excess pressure. The purpose of the one in the oil pump is to regulate or dump off pressure after it hits a set amount, probably around 80psi or so. The second regulating or relief valve opens to dump excess pressure to lower the oil pressure to the supply line to the oil cooler and the turbo on "T" models. Look up dual relief VW type 1 engine to get a good idea of how a two valve system works.



My point was and is the issue of reduced flow to the valve train is of more concern than the lowish oil pressure. If the regulating valve in the oil filter housing is getting stuck open this is the same as having excess clearance someplace. The valve is there to regulate the oil pressure to the cooler, not the main oil gallery. Will the oil pressure drop if it's stuck open? Sure because you effectively now have a 10mm hole in your oil gallery.



Is the problem likely a stuck regulating valve in the oil filter housing? I would say yes. But if that doesn't solve the problem of BOTH the oil pressure and the low flow to the rockers my opinion would be you need to find where the excessive clearance problem is. Which unfortunately means pulling the motor. So hopefully the worst case scenario here is the bore is worn on the filter housing and is causing the piston of the regulating valve to get stuck open thereby creating excess clearance and dumping pressure and flow into the oil pan.

Yes agree with this but his FIRST analysis has to be if the oil pressure gauge is working properly.
I replaced the 36-37 year old rear crankshaft seal on our yanmar engine ( Didnt buy a Yanmar seal as I'm not a merchant banker, just a seal from SKF or Saeco equivalent) The crankshaft had 0.1mm play& the max in the workshop manual is 0.04mm frm memory. That ancient seal only leaked a little but still your analysis is right I THINK as age is not kind to us or seals
Agree gain that little flow to rocker cover is a major concern if thats his only change.
Makes me wonder how OP could operate for 6 years with a major problem tho. He did I THINK say dry about the v/v train is recent.
My thought was maybe a blocked oil gallery BUT hard to see how anything big enuff to block an oil gallery can make it past the oil filter.
So ya go back to the suction pipe. On our engine we had major sludge maybe 1/2" thick when I dismantled it. Gauze filter on the inlet pipe had some kinda buildup on it which I removed with solvent & water blaster or pressure washer in American. It was amazing bad, may have caused our initial problem of oil pump failure. BUT I know of 3 of these engines that have too big clearances in the oil pump. They manifest themselves in low oil pressure. OP's initial oil pressure sounds ok but it's heat & viscosity related.
Oil pump is last thing to check in OP's case is my guess
OP says sump & suction pipe clean so THINK he's ok there
It's a brain worm & I'm avoiding chores whilst having a beer
If the OP has a workshop/ service manual can he post an oil flow schematic?
I saw CassidyNZ's one but be nice to know it's the same.
My GUESS is still pressure gauge or PRV but I'm just a tinkerer
Dunno why I like engine threads so much as we much prefer sailing.

[jimbunyard]

The difference is certainly not semantics because the different valves perform different roles, as you yourself state; the valves could be identical in construction yet they have different roles to play, which is why one is known as a relief valve and the other is known as a regulating valve, regardless of what they're called in the service manual.

Here's a link to the service manual that has the information about the oil flow; below are the relevant pages from the service manual describing the different roles the valves play (as can be read, the description given above for the regulating valve's operation [I quess for VW's valves} only roughly echoes the one given for Yanmar's). I'm not sure why people insist on using information from different manufacturers to explain how another manufacturers' product operates.

https://www.manualslib.com/manual/73...age=128#manual

Almost certainly the seal's demise was caused by 27 years and 6500 hours of use, and the dry rocker shaft is of course the most concerning issue.

If, after determining that the gauge and alarm switch are reporting accurately, and after cleaning the regulating valve, there's no improvement, as prevously advised I wouldn't hesitate to flush the engine with a diesel-heavy mixture of oil and diesel in the manner detailed...but that's just my mean nature showing itself.

[wingssail]

For those of you following this, I am back in port and I have found a mechanical gauge and attached it in place of the oil pressure sensor and electric gauge

I ran the engine under load (in gear) at 1800 RPM at the dock for 1 hour and 30 minutes.

The results:

• The engine reached operating temperature of 79 on the temp gauge and 71 degrees on the head surface using the laser thermometer.
• The oil pressure on the mechanical gauge was 55lbs the whole time, never varied even a lb.
• The Low oil pressure alarm did not sound except when the engine was stopped. (I had removed it but I was unable to replace it because the replacement had the wrong threads, so I put it back in)
• The rockers (inside the oil filler cap) look clean but only slightly damp. I touched the shaft with my finger and it came out wet (see photo)

So at this point I feel quite a bit better. At least I know there is oil pressure.

I don't know if I should be worried about the lack of flowing oil at the rockers or any other of my findings. Ideas anyone?

If I can find a way to reduce the thread slightly and install the new low oil pressure switch I will do that and I will run the engine some more. I am also going to order a new oil pressure sensor unit and a Yanmar standard low oil pressure switch. (and a T so I can have both the electrical gauge in the panel and the mechanical one in the engine room.)

What size die should I buy to run those male threaded adaptors with? Would a R 1/8" 28 bspt taper pipe die be correct? I can look for that.
Pressure at 1800RPM

Pressure at idle when hot

Rocker shaft viewed through oil filler cap

Wet finger after touching the rocker shaft

Thoughts or ideas?

[wingssail]

Originally Posted by jimbunyard

The difference is certainly not semantics because the different valves perform different roles, as you yourself state; the valves could be identical in construction yet they have different roles to play, which is why one is known as a relief valve and the other is known as a regulating valve, regardless of what they're called in the service manual.

Here's a link to the service manual that has the information about the oil flow; below are the relevant pages from the service manual describing the different roles the valves play (as can be read, the description given above for the regulating valve's operation [I quess for VW's valves} only roughly echoes the one given for Yanmar's). I'm not sure why people insist on using information from different manufacturers to explain how another manufacturers' product operates.

https://www.manualslib.com/manual/73...age=128#manual

Almost certainly the seal's demise was caused by 27 years and 6500 hours of use, and the dry rocker shaft is of course the most concerning issue.

If, after determining that the gauge and alarm switch are reporting accurately, and after cleaning the regulating valve, there's no improvement, as prevously advised I wouldn't hesitate to flush the engine with a diesel-heavy mixture of oil and diesel in the manner detailed...but that's just my mean nature showing itself.

Mr Bunyard, your advice struck me (along with Scubaseas, Compas798 and others , thank you all) as thoughtful and knowledgeable.

After reading my update would you still recommend flushing the engine, and exactly how should I do that? and how many times do I change the oil afterwards to get the diesel and "stuff' out?

[Scubaseas]

The difference is certainly not semantics because the different valves perform different roles, as you yourself state; the valves could be identical in construction yet they have different roles to play, which is why one is known as a relief valve and the other is known as a regulating valve, regardless of what they're called in the service manual.

Both are piston driven springs that dump excess pressure back into the oil sump. They both do exactly the same thing and if the 3JH2 is like my 4JH5E they would both do it at the same pressure, So I stand corrected they do not regulate the oil cooler pressure, It's just a redundant set up which is kinda stoopid in my opinion.

I'm not sure why people insist on using information from different manufacturers to explain how another manufacturers' product operates.

Umm because they work on the exact same principles regardless of the manufacturer.



If you want to believe they are separate things and work differently I am not going to change your religion. If you need to be right, fine your right

[Compass790]

After reading your update I'd say the sump & suction pipe will be fine, no need to flush.
Good that you have excellent oil pressure. Bet you glad you checked with another gauge. I'll let someone who has or knows your engine comment on the oil amount in top-end. Seems like not enough to me if you took your pic straight after shutdown but I'm more used to looking at black oil.
Did you try removing rocker cover oil cap whilst engine is running & see if it's spraying in there?

[Scubaseas]

Wingsail:


I would not try to rethread a sender. You can buy adapters prethreaded or just get the right sender. Take the original to your local autoparts store or a machine shop for them to determine the threads. I am sure you can get a non Yanmar (like a VDO, Faria or Nissens) that will meet spec and not cost a ton. Got a picture of the offending sensors?



Can you use diesel fuel as a flush? Sure. Does it have any where near as much detergent as a product designed to clean sludge? no. Would I personally use diesel fuel to flush out a motor? no. Professionally as a mechanic would I? Hell no just from the liability stand point. I would use Rislone "Engine Treatment" if available or Marvel "Mystery Oil". Follow directions. Pretty much pull out some oil, put the stuff in, run it 5 to 10 hours and then change the oil. If the filter you take off after the flush is heavy and full of sludge (cut it open) you may want to change the filter again after the oil change after maybe 1 hour.


At first glance your rockers look OK. As long as the oil gets down to the valve you're fine. Maybe buy a valve cover or bonnet gasket, take the cover off and adjust the valves while your at it. Run the engine briefly with the cover off and see how much lube you are getting and to where. As long as a drop of oil is reaching the valve stem you are OK. If the oil is dumping out at the shaft and not getting to the end of the rocker you might need bushings or have clogged passages. They look nice an clean however. Taking the cover valve off can also give you a better idea about what if any sludge you have going on.



Given the age of the motor you might want to pull an oil sample for testing. It usually runs about $40 and can tell you a lot about what is happening inside the engine.

[Scubaseas]

If I can find a way to reduce the thread slightly and install the new low oil pressure switch I will do that and I will run the engine some more. I am also going to order a new oil pressure sensor unit and a Yanmar standard low oil pressure switch. (and a T so I can have both the electrical gauge in the panel and the mechanical one in the engine room.)

Careful with a tee. They tend to crack with the vibration of a diesel and the weight of the tee and two sensors. Better to run a pressure rated oil hose up to a tee mounted off engine.


Rethreading a sender will weaken the threads. If it snaps off you will pump the oil out of your engine and bad things will happen.

[a64pilot]

55 Psi is great, what will tell the tale though is hot pressure when idle, that’s when engines with worn parts shows up, but 55 PSI is well within limits I’m sure without looking anything up.

Reduced oil flow to the rocker arm assy could be from restricted passages, the oil that flows there is not under much of any pressure, it’s just flow through a relatively small passage, if there were 55 PSI at the rocker arm you would pump the valve cover full of oil.

However, personally I would never run Diesel fuel in oil to clean things out myself, it’s likely effective, but there are products specifically made just for that purpose, some engine flushes are literally just mineral spirits and they tell you to run it for 5 min and drain.
I would avoid those as well, mineral spirits won’t lubricate anything and is just a solvent, which is the point.
I would run either sea foam, or I would put one quart of ATF in with oil changes, run a high grade of oil, likely straight 40W Rotella as the ATF will thin it somewhat, and change it at 100 hour intervals or if you see a pressure drop. If the cold oil valve opens due to a clogged filter, you should see a drop in pressure, but I bet that won’t happen.

However if the pan and valve cover are clean, it’s unlikely you have a problem, pan gets it from gravity of course and the valve cover forms a gum or varnish because oil vapor condenses on it because it’s the top and is cooler than the rest of the engine.

Remove the rocker arm which of course is easy to do and see if there is junk inside of it, many engines flow oil though the rocker arm to oil the rockers, but the top end just needs a little oil, it doesn’t need pressure or serious flow.

My gut feeling is that you don’t have a problem, and are just looking hard at things which you wouldn’t normally do.

On edit after reading some other posts, MMO is fine, been around longer than we have.
And the post about T’s is spot on, the weight added with vibration may well crack the pipe where it screws into the engine.

I put a sending unit into an unused galley on my engine, there are a few, on mine one was right by the filter, unscrew the plug, run a 1/8” NPT tap into it with grease on the tap and thread in the sender. Leave the stock stuff alone, that avoids T’s and is a cleaner install.
But I would also go to a 100 hour oil change interval for a couple of reasons, first older engines need more frequent oil changes than newer ones, the reason is they have more blow by and that contaminates the oil, secondly in your case because you have a lot of low load running which has a tendency to not get the oil hot enough to cook off moisture, moisture with combustion products form acid which is a bad thing of course and it also forms sludge.

Then lastly, buy a Honda and off load all those hours onto the Honda, and avoid an expensive engine overhaul in the future.

[wingssail]

OK, I'm taking this all on board and I'm glad to have experienced people giving me the benefit of your experience. On this topic I have little.

OK I've probably not got an oil pressure problem except remaining concern about the oil supply to the rockers. I'm going to pull the rocker cover off, (I've done it before to replace ahead bolt) and observe the oil flow all along the rocker shaft.

I will add an engine flush product and follow the directions in the hope that the passage to the rockers will open up. I will change the oil at 100 hours (or there abouts).

I will not add a T, (very good points on that, thanks) and I will get properly sized yanmar sending units (it just means waiting, importing in Mexico is slow).

An with that I will end this thread so as not to bore you all with what might well have been a false alarm.

Thanks Again

(Now I have to go replace my 10 year old blown up charger/inverter. Do projects ever end?)

[Sailing August]

You can try increasing the viscosity of the oil and see if the pressure rises. If it does then you probably need a main bearing and con-rod bearing overhaul.....which basically means a complete engine overhaul.
As the clearance in the bearings opens up due to normal wear the engine will increasingly loose oil pressure.
Also, check to see if your oil pump has a pressure by-pass that may be malfunctioning.

[Compass790]

Originally Posted by wingssail

OK, I'm taking this all on board and I'm glad to have experienced people giving me the benefit of your experience. On this topic I have little.

OK I've probably not got an oil pressure problem except remaining concern about the oil supply to the rockers. I'm going to pull the rocker cover off, (I've done it before to replace ahead bolt) and observe the oil flow all along the rocker shaft.

I will add an engine flush product and follow the directions in the hope that the passage to the rockers will open up. I will change the oil at 100 hours (or there abouts).

I will not add a T, (very good points on that, thanks) and I will get properly sized yanmar sending units (it just means waiting, importing in Mexico is slow).

An with that I will end this thread so as not to bore you all with what might well have been a false alarm.

Thanks Again

(Now I have to go replace my 10 year old blown up charger/inverter. Do projects ever end?)

Not bored at all, good chore avoidance stuff trying to nut out your problem
I'd just look in the rocker cover oil filler cap to see what oil flow is like whilst engine is running before I pulled it off unless you want to check tappet clearances at the same time.
I have more to say on senders & tees but no time at present.
No need to get gold plated Yanmar one.