Yanmar 6lpa 0 oil pressure

micky · Post by **micky** » May 22nd, '22, 19:01

I have 2 Yanmar 6lpa-dtp. Both were repaired to 0 hours. Started them up on friday for the first time and noticed one of them had low oil pressure (19 psi cold), gauges are mechanical. In the afternoon it went up to 40 psi.Yesterday it was at 12 psi so I let the mechanic that repaired them know. Went today to the boat and tested the engine with 2 additional mechanical gauges and the pressure was 0.

What can be the cause of this? Oil pump?

micky · Post by **micky** » May 22nd, '22, 19:23

Yesterday:

Today:

Amberjack · Post by **Amberjack** » May 23rd, '22, 13:48

Micky-I'm not a mechanic but I've had Yanmar 6LP's for 18 years and never heard of this issue. Until someone more mechanically on the Forum replies here are my thoughts. It sounds as though you're starting from a complete rebuild and this will be the first run. Are you sure you have enough oil in the pan? That's the easiest first step. Should be 10.5 liters. The dip sticks on these engines are difficult to get a good read. Pull it out, wipe it and reinsert leaving it about an inch high for 10-15 minutes. Then insert completely and check. The dipstick cap apparently causes a seal which prevents oil from registering in the tube unless the cap is cocked open.

It really sounds like this is an oil pump issue and if you're lucky the drive train is somehow not connected. Or the pickup from the sump to the oil pump was not re-installed after the rebuild. Either makes sense if the engine was partially disasembled and put back together again. My layman's thoughts. I'd be reluctant to turn it over any more without resolving the issue.

Bruce · Post by **Bruce** » May 23rd, '22, 18:00

What was done to the engines?

micky · Post by **micky** » May 23rd, '22, 18:47

EVERYTHING. They were taken to a bare block and everything was installed new. Today the mechanic told me that he only installed 1 new oil pump, on one of the engines he used the old one. If you open the oil cap with the engine running, you see the oil circulating on the engine. He thinks its the pressure relief valve that its stuck open. He's going to the boat on thursday.

https://imgur.com/cQlsWCI

Carl · Post by **Carl** » May 24th, '22, 08:46

A pressure relief valve would be nice...

I "think" at least the engine would have some lubrication flowing in that scenario. This is one of those I'll shut up and keep my fingers crossed for you times.

scenarioL113 · Post by **scenarioL113** » May 24th, '22, 19:15

This goes without saying....

OIL PRESSURE is the LAST thing you mess around with.

If your mechanical gauges are reading "zero" DO NOT RISK IT! You can burn up main or cam bearings quickly. I do not know anything about Yanmar engines but oil PSI is oil PSI.

I agree it sounds like some regulator / pressure valve but you need to solve prob before you drive it. I recommend you only run engine to check PSI until it is solved and do not run it for more than a few seconds at a time.

I had an issue many years ago on a cummins and in that case it was the oil pickup tube gasket giving me grief

scenarioL113 · Post by **scenarioL113** » May 24th, '22, 19:24

Furthermore,

I "think" you have a "vane" style oil pump like most engines. Yes like anything else they can go bad BUT I tend to think it may be something else. These oil pumps are pretty damn reliable and really would need to come apart to stop working (IMO). Low oil PSI is one thing BUT ZERO??? If it is oil pump then zero would be catastrophic failure of the pump. Low PSI then it is worn out... One or the other...

Can you pull the oil pump? Swap it from the other engine if it is not too difficult and that will tell all...long before Thursday.

Do you have the Yanmar manual for troubleshooting?

Dont mess around with this, you have come this far buddy and worked your ass off so try to be patient and please post so we can try to help you

scenarioL113 · Post by **scenarioL113** » May 24th, '22, 19:37

Right from the Yanmar manual

Clogged engine oil filter Replace
Engine oil temperature too high Check the seawater level
Failure of oil pump Overhaul or replace
Faulty operation of oil pump relief valve

https://www.google.com/url?sa=t&rct=j&q ... qVq0J6xBY5

micky · Post by **micky** » May 24th, '22, 20:17

To replace the pump, the front of the engine needs to be disassembled. I replaced the oil filter on saturday. I wont touch the engine until the mechanic goes to the boat as he’s the one who overhauled it and they are under his warranty.

micky · Post by **micky** » May 29th, '22, 05:54

I think I found the problem. The springs on both oil pumps have been altered…. Badly plus the relief valve inside the pump doesn’t want to come out so maybe its getting stuck and thats why sometimes I have pressure and sometimes I don't.

I already ordered the 2 springs and the 2 relief valves. Also contacted a mechanic that specializes in the 6LP and he’s coming next week. I told him to do a complete survey on both engines and give me a report so that I can have it if I need to go to court with the other guy.

Spring from the low pressure engine, you can see it stretched in the middle:

Spring from the good pressure engine:

Comparison between the 2:

Yesterday I wasn't able to remove the relief valve from the low pressure engine (goes in front of the spring), so decided to mess with it today and was able to take it out. As soon as I had it in my hands I knew something was wrong as the 4 holes it has the edges had burr like if they had been drilled and all the edges of the relief valve were sharp, and it had scratches all over it so I sanded it with 2000 and 3000 grit and then using a file I eliminated the burr on the 4 holes. Installed it back and pressure went up to 40 psi, left the engine running and in 15 minutes, pressure was down to 15 psi.

Decided to remove the relief valve from the other engine and thats when I saw what had been done to the other one, the 4 holes had been drilled and also the piece had been cut.

Relief valve from the low pressure engine:

Relief valve from good engine:

The 3 differences between both relief valves are: the size of the holes, the distance between the holes and the lower part, the width of the lower part (has been cut).

scenarioL113 · Post by **scenarioL113** » May 29th, '22, 10:28

interesting

I wonder what the prob was that someone had to file or "fit" the part.

In my opinion that part needs to be replaced if it has any problem working when it is test fitted and or assembled. It is a critical component. Maybe the unit is from a different model yanmar and was close to the same and made to fit when overhauled the last time???

See how available and how much the price is for a new one and that may answer the question...

just bc they look different does not mean that it is incorrect, many times they update parts for better operability or to save on machining costs etc....
if that is the case tho I think it would go hand and hand as an entire relief valve

micky · Post by **micky** » May 29th, '22, 16:12

I ordered 2 springs and 2 relief valves on friday but they will take 3-4 weeks as they were ordered in japan.

Rawleigh · Post by **Rawleigh** » May 29th, '22, 19:42

At least they will be right though!

Carl · Post by **Carl** » May 30th, '22, 07:54

Rawleigh wrote: ↑May 29th, '22, 19:42 At least they will be right though!

You would hope that would be the case.

I’m not a spring guy, but those look like something I’d do to fudge a temporary fix to get by for now, till new parts arrived.

It goes back to what the words complete overhaul actually mean. I’m sure Micky was thinking everything checked and inspected from A-Z and the mechanic was on a different page. Perhaps more, take apart, go over and check the items expected to wear…see if anything “jumps” out at you as being wrong. Very different jobs that can have very different outcomes.

Now if the valve was hanging up and he rigged it up to work by tweaking spring and playing with valve AND not telling you that is such a different story.

Carl · Post by **Carl** » May 30th, '22, 07:57

Rawleigh wrote: ↑May 29th, '22, 19:42 At least they will be right though!

You would hope that would be the case.

I’m not a spring guy, but those look like something I’d do to fudge a temporary fix to get by for now, till new parts arrived.

It goes back to what the words complete overhaul actually mean. I’m sure Micky was thinking everything checked and inspected from A-Z and the mechanic was on a different page. Perhaps more, take apart, go over and check the items expected to wear…see if anything “jumps” out at you as being wrong. Very different jobs that can have very different outcomes.

Now if the valve was hanging up and he rigged it up to work by tweaking spring and playing with valve AND not telling you that is such a different story.

Sorry for the BS you are dealing with, on a good note you didn’t decide the alarms and gauges are wrong, than decide I’m going to take her for an all out sea trial.
That would be bad.

micky · Post by **micky** » May 30th, '22, 09:16

Carl, I also ordered a complete oil pump. So that I can have it on hand if the new spring and valve doesnt work. If it works I’ll send it back.

My temp and oil psi gauges on the bridge are mechanic. I also installed 2 different mechanic oil psi gauges on the engine room so I knew it wasnt the gauges.

micky · Post by **micky** » Jun 15th, '22, 17:11

I got the relief valves today. The springs still haven't arrived. I installed the relief valves and the oil psi still went down but it took muuuuch longer to go down. Before in 1 minute the pressure went from 40 to 18, now it took around 20 minutes. Both the mechanic and my dad told me that without the new springs I'm loosing my time

. I'll install them as soon as they arrive and report back.

Here you can see the difference between the new (right) relief valve and the home made one (left).

4:23pm

4:45pm

Carl · Post by **Carl** » Jun 16th, '22, 11:10

The valve on the left is different for sure, but I am not sure it's homemade. I'd guess it is from a different application as the machine marks look consistent.

Then again I guess as good as I bet and I would lose a bet in a one-horse race.

Bruce · Post by **Bruce** » Jun 17th, '22, 09:23

Some may know that the 6lp is based on a Toyota over the road engine adapted to marine use by Yanmar.
During my time as a Yanmar dealer I saw some parts that came from the over the road engine used on the marine although pretty much most parts were not interchangeable although some tried.

The difference in those cups may be that.
A questionable rebuilder looking to save costs and time might do that.

Bearing clearance affects oil pressure when oil gets hot also.

micky · Post by **micky** » Jun 17th, '22, 16:09

Hey Bruce, I’m really starting to think about taking that engine out of the boat and opening the engine to check bearings, oil pump, etc. The only thing holding me is thinking about disassembling the whole salon, door, etc.

scenarioL113 · Post by **scenarioL113** » Jun 17th, '22, 22:03

Micky,

If you are still waiting for the rest of the parts of the oil pressure regulating valve than just wait till you get them. I know it is frustrating but at least if after that you still have a problem then you know that you did all that you could do...

Bruce is correct that the bearings will affect the oil pressure and will show low PSI when the oil is at operating TEMPERATURE if they are suspect. The PSI regulating assemble can give similar symptoms as well so you need to confirm it is in spec.

If you ran the engine for any significant time at 0 PSI then that could have cooked one or more of the bearings that would give you the readings you are seeing now unfortunately...
Now that you may have corrected the regulator problem, you may have caused a problem while troubleshooting...

This situation can be very much like a dog chasing his tail...you may have fixed a problem but created a problem inadvertently. Ask me how I know... SMH

I say you get the new springs and all the "NEW" parts installed and see where you are at...if problem persists then you need to pull the CAM and the CRANK and have a shop "MIKE" them up to see if they are in specification

...I wish I was down there bc I would shoot over there in a second and get my hands dirty with you...

micky · Post by **micky** » Jun 19th, '22, 10:32

The springs should be here on Wednesday and the oil pump on Thursday. I'll install the spring and if it still does the same, over the weekend I'll remove the oil pan and put oil pressure through the block to see if the bearings have oil drops or a stream. If its oil drops I'll replace the oil pump, if its a stream, engine is coming out.

micky · Post by **micky** » Jun 21st, '22, 19:45

Springs are here, will install tomorrow afternoon and report back. Also received the new oil pump.

Carl · Post by **Carl** » Jun 22nd, '22, 06:07

I have my fingers crossed for you!

micky · Post by **micky** » Jun 22nd, '22, 18:11

You can un-cross them. Spring did not fix it. This weekend I’m dropping the oil pan and injecting oil with pressure to the block via the sender fitting to see if the bearings leak (drop or stream). If they do, engine is coming out. If not, I’ll replace the oil pump.

Tony Meola · Post by **Tony Meola** » Jun 22nd, '22, 20:59

Ugh. We feel for you.

Carl · Post by **Carl** » Jun 23rd, '22, 06:26

I am going out on a limb here saying this is a sore spot between the place that overhauled and you.

Is the place trying to make this right for you?

micky · Post by **micky** » Jun 23rd, '22, 10:29

I haven’t contacted them again as I wanted to see if the spring and relief valve fixed the issue. I’m dropping the oil pan on saturday and doing the oil drop test, if its the bearings I’ll give the guy a call. If its not that, it should be the oil pump.

micky · Post by **micky** » Jun 25th, '22, 09:51

Engine has to come out, bearings are leaking BIG TIME. I’ll post the video later tonight.

micky · Post by **micky** » Jun 26th, '22, 12:40

Took the engine out yesterday. Removed 2 of the pistons bearings, bearings are new, but look at the condition of the crankshaft. When I did the oil test the main bearing leaks like an open faucet. Look at the pic with the blue arrow. Another thing is, look at the bolts, black oil, smelled like burnt oil, like if nothing was washed before assembly.
Spoke to the mechanic and he told me he would take care of it so lets see how it goes.

Tommy · Post by **Tommy** » Jun 26th, '22, 14:09

I hate it for you, Mickey. You are obviously a man that goes out of his way to do everything right, but it appears that you're dealing with a mechanic who has cut some corners. Let's hope he stands behind his work and makes everything right. Of course, none of your sweat equity or down time cane be replaced......

mike ohlstein · Post by **mike ohlstein** » Jun 27th, '22, 00:48

They never touched the bottom end.......

micky · Post by **micky** » Jun 27th, '22, 05:45

Thats what my dad said.

Carl · Post by **Carl** » Jun 27th, '22, 09:53

I want to give that guy the benefit of the doubt, but he has made that very hard after seeing those pictures.

Skipping those steps makes me wonder what else was skipped...I can only imagine what is going on in your mind. Sorry, as Tommy said I hate it for you.

scenarioL113 · Post by **scenarioL113** » Jun 27th, '22, 10:03

If he did touch the bottom end then he never had the crankshaft checked to see if in specification.
Anytime you pull an engine apart and you are just not sure of how it was running before you ran it then you MUST have the crankshaft checked.

Micky you are warrior with this project and in the end it will be ALL OK

That crank needs to goto the machine shop to see if it is serviceable. They can cut it and you can run oversized bearings but that is for the machinists to figure out.

scenarioL113 · Post by **scenarioL113** » Jun 27th, '22, 10:06

If the guy is gonna jerk you around just bring the crankshaft right to the machine shop and let them tell you what condition it is in

Stephan · Post by **Stephan** » Jun 27th, '22, 11:33

Micky-
Sorry for this ordeal but thank you for sharing it so we can learn.
Stephan

micky · Post by **micky** » Jun 27th, '22, 12:14

scenarioL113 wrote: ↑Jun 27th, '22, 10:03 If he did touch the bottom end then he never had the crankshaft checked to see if in specification.
Anytime you pull an engine apart and you are just not sure of how it was running before you ran it then you MUST have the crankshaft checked.

Micky you are warrior with this project and in the end it will be ALL OK

That crank needs to goto the machine shop to see if it is serviceable. They can cut it and you can run oversized bearings but that is for the machinists to figure out.

I hope its usable as a new one is over $7k.

scenarioL113 · Post by **scenarioL113** » Jun 27th, '22, 16:49

From the pics you posted Micky, I would say it is usable as it does not appear to be galled or have catastrophic failure. Get it to a machine shop ASAP!

Like I said if you were able to do this much (dropping the pan and pulling the journals) than you are half way there....just take care of it yourself.

Let him cut and or spec the crank and new bearings and slap it in...

Have the machine shop 100% CONFIRM that it is indeed the crankshaft is causing the problem. They will 100% let you know if it is messed up. Cam bearings could cause low oil PSI as well but from what you posted I am still thinking your crankshaft

micky · Post by **micky** » Jun 27th, '22, 20:49

Spoke to the mechanic today and showed hm the pics I took yesterday, he asked if I could take pics of the bearings so I did that, I was able to remove cylinders 1,3,4,6. Cylinders 2 and 5 I was unable to loosen them up. Cylinder 6 I was able to loosen the bolts with 1 hand and without doing any kind of force so who knows if that is the issue. I'm thinking none of them were torqued to specs because of 2,5 and 6.

1

3

4

6

CamB25 · Post by **CamB25** » Jun 28th, '22, 05:41

I'd be tempted to plasti-gage the crank and rod journals before moving forward. Does plasti-gage still exist? it's been a while for me. Anyway , the point is to understand the fit, or clearance, between all the journals and all the bearings.

scenarioL113 · Post by **scenarioL113** » Jun 28th, '22, 07:14

cylinder 6 being able to remove by hand raises my eyebrows. A loose cap will give oil PSI loss when the engine gets upto operating tempereature.

I dont know if it is feasible to run the engine on a pallet to see if that corrects the problem. You say , you can NOT loosen the other ones? Why? (are they too tight??? and you fear breaking something???)

The loose cap could be from possibly not spinning the crank when torquing the cap bolts and measuring how easily the crank spins by turning by hand... maybe something was causing interference in the bearing when setting the cap....idk maybe something like that. I dont rebuild engines every day but I have built a number of them.

Everything needs to be super super clean when installing the crank and cam...more so when dealing with bearings...any little thing can ruin your day

micky · Post by **micky** » Jun 28th, '22, 07:28

If you see pics 4 and 5, the black dot is dirt embedded into the bearing. 2 and 5 are extremely tight. I didn't have a breaker bar with me yesterday.

micky · Post by **micky** » Jun 28th, '22, 08:36

CamB25 wrote: ↑Jun 28th, '22, 05:41 I'd be tempted to plasti-gage the crank and rod journals before moving forward. Does plasti-gage still exist? it's been a while for me. Anyway , the point is to understand the fit, or clearance, between all the journals and all the bearings.

Still exists and the service manual says it HAS to be used.

Rawleigh · Post by **Rawleigh** » Jun 28th, '22, 09:34

I hope the cam bearings are OK! The problem I see with getting the same guy to do it is he has already exhibited sloppy workmanship and I doubt the workmanship will improve when he is doing it for free!!! You are in it this far yourself, so I would plastigage it so you know what you are starting with and then get the machine shop to dot he hard work and you install it yourself. You will need a good torque wrench if you don't already have one. At least you will know it was fixed right! I am sure Bruce and the other diesel guys on here can talk you through it.

Carl · Post by **Carl** » Jun 28th, '22, 10:28

Rawleigh wrote: ↑Jun 28th, '22, 09:34 The problem I see with getting the same guy to do it is he has already exhibited sloppy workmanship and I doubt the workmanship will improve when he is doing it for free!!!

What Rawleigh said is something I was thinking and did not want to say.

I was hoping to hear in one of the conversations with the "mechanics shop" that he had one of his guys doing the work. Correcting the issue by saying What is being found now is not tolerable and he'll be picking up the "motors" to go through "them" with a fine-tooth comb and that guy who did the work will more likely than not be let go. I'm thinking that ship has sailed...

micky · Post by **micky** » Jun 28th, '22, 12:42

He did told me that he will take care of the situation and that if his work failed he will take care of everything. I know it did. My plan is to take a few vacation days and be present when he's asembling everything.

Carl · Post by **Carl** » Jun 28th, '22, 14:36

micky wrote: ↑Jun 28th, '22, 12:42 He did told me that he will take care of the situation and that if his work failed he will take care of everything. I know it did. My plan is to take a few vacation days and be present when he's asembling everything.

your a smart man.

micky · Post by **micky** » Jun 30th, '22, 14:40

Mechanic was supposed to come yesterday to check the engine and never arrived, then he told me he was coming today and he cancelled so I’ll disassemble it myself, order the parts, take the crankshaft to a machine shop and will hire a Yanmar mechanic to assemble it back.