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Old 06-30-2008, 06:58 AM   #1
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L.O. Pressure

I know in my profession I am supposed to have the answers.
When I start my engine the LO pressure shoots up to 10 bar (150 psi) when the engine RPM are raised.
This pressure should be maintained at 5.5 bar by the relief valve.
Once the engine warms up the relief valve works and the pressure settles at the required 5.5 to 5.8 bar (75 to 80 psi)
Due to my cooling configuration the engine takes about 20 min to warm up.
I know the answer is to probably drop the sump and change the relief valve but has any one experienced this before and how did you get around it.
I am living with the problem at present and just taking care during the first 1/2 hour.

Benn
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Old 06-30-2008, 08:39 AM   #2
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RE: L.O. Pressure

It sounds to me like you've found the culprit. Everything you've said points to the relief valve. One thing you might try is to clean the valve without removing it. A couple of quarts of ATF in the crankcase just might have enough detergent in it to clean it up and start working correctly again.

If you're close to an oil change anyway it won't hurt. Just remember not to run the engine hard with the ATF inside. Normal running, i.e. 1750 RPM on a Lehman for example will not cause any extra wear.

Of course the problem might run deeper. Why is the relief valve gummed up? Most of the time it is from not changing oil often enough or from the wrong type of oil being used. Years ago it was common for things to gum up when someone changed from plain oil to detergent oil. All the deposits which were caked onto the inside of the engine got disolved and circulated thru the engine parts and wrecked havoc. I doubt that's the problem here. I would look closely at the oil I used and see if the temp rating, detergent rating and other specs met the way I used the engine.

Try the ATF, you might be surprised at the result.

Ken
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Old 07-01-2008, 03:22 AM   #3
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RE: L.O. Pressure

Even a hard working engine will have enough lubrication with 10% ATF .

The thinner viscosity will only result in a tiny bit higher oil burn per hour , but no loss of oil pressure .

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Old 07-01-2008, 06:55 AM   #4
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RE: L.O. Pressure

OK Thanks Guys must give it a try when I get close to my next oil change.
Not far away as I have just completed a 65 hour trip up the coast. ( Queensland Australia)
By the time I complete my cruising up North I will be ready for an oil change before heading south and home.
I will let you know how it goes.
Benn
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Old 07-01-2008, 09:58 AM   #5
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RE: L.O. Pressure

The seal between the fuel pump and the oil failed so diesel was being mixed in with the oil which cleaned the engine like new.* The oil level was 1 to 2 inches abobve the full mark, about 1 gallon.* * There have been a number of fuel pump seal failures especially since the new low sulfur diesel, so check your oil regular and if the oil level is high its proable the fuel pumps seal.* Anyway it will clean the engine.
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Old 07-02-2008, 03:38 AM   #6
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RE: L.O. Pressure

For the ATF to work it needs time and temperature.

If you can run it when homeward bound (for a good bunch of hours) and change the oil IMMEDIATLY on stopping the engine.

Pump out out when its nice and hot , and carries all the gunk its detergents pulled loose.

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Old 07-02-2008, 09:01 AM   #7
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RE: L.O. Pressure

When I start my engine the LO pressure shoots up to 10 bar (150 psi) when the engine RPM are raised. ... Once the engine warms up the relief valve works*... the engine takes about 20 min to warm up.

I know the answer is to probably drop the sump and change the relief valve but has any one experienced this before and how did you get around it.

I am living with the problem at present and just taking care during the first 1/2 hour.

*
Is this a new issue? Has the oil pressure been creeping up since you got the boat? Is it colder now than before? Have you changed lube oil type?

*
The events you described sound perfectly normal for an engine started cold. There are a few details missing that might help explain the phenomenon; make and model of engine, type and weight of oil, ambient temperature at start, pressure at idle rpm on startup, rpm at which high oil pressure is produced, and oil pressure at warm idle and warm high rpm.

*
If you have a single viscosity oil and it is cold at startup the oil pressure (as you well know) will be higher than when warm. The relief valve is not very large and increasing the rpm with cold viscous oil is going to create more pressure than the limited flow through the relief valve can accomodate. The best way to handle the situation is to restrict high rpm operation until the oil has warmed up. If you need to get out of town in a hurry, install a preheater of some sort.

*
You mention that everything is normal after a 20 minute warmup and that sounds normal. Unless you have an engine preheater to keep the lube fluid, any high rpm operation will starve the valve gear so that is another reason to avoid running it up cold. Another question, how accurate is the gauge?

*
I would avoid mixing mouse milk or ATF with lube oil. It might clean the oil passages but it will also reduce viscosity and lubricating qualities.

Rick
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Old 07-02-2008, 09:47 PM   #8
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RE: L.O. Pressure

Rick B ,
Yeah I know what you are saying.
No this was a new phenomen that started about 18 months ago and suddenly it did not creep up over time.
Normally on start up the relief valve would control the oil pressure at 5.5 to 5.8 bar may be a bit higher 6.2 bar then drop when warm.
But of late until the engine warms up LO press is high with higher RPM ( 10 plus bar) and then settles , that is why I have not been too worried.
Gauge pressure is good as I have checked it against a master gauge.

The engine is an IVECO 8210M 14 lt naturally aspirated engine.
220 HP at 2200 RPM
I run at 1530 RPM giving good load and torque, 50 Hz on my 5 KW engine driven 240 V generator and 8 knots.
I use Shell Rimulex 15 W 40 engine oil and this has been pretty consistant throught out the life of the engine since I rebuilt it when I built the boat

Benn
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Old 07-03-2008, 04:05 AM   #9
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RE: L.O. Pressure

"It might clean the oil passages but it will also reduce viscosity and lubricating qualities."

WRONG ,

as usual.

The Viscosity of the oil has almost nothing to do with the lubricating qualities , only with oil consumption rate .(assuming your not lubing with tar)

ATF is a fine lubricant in its own right , as many owners of old old diesels use a quart in a 100g to help out with the newest "fuel".

The "fuel" today DEPENDS 100% on the local deliverer to add the additives that claim to stop excessive wear from the product.

"Their's many a slip"

Is why so many OTR folks will pay for an extra quart of ATF , and anyway it burns well too.

Other folks simply fill the fuel filters on changeout , and let the ATF clean the injectors a bit , .

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Old 07-03-2008, 09:10 AM   #10
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RE: L.O. Pressure

The Viscosity of the oil has almost nothing to do with the lubricating qualities , only with oil consumption rate .(assuming your not lubing with tar)

*

ATF is a fine lubricant in its own right , as many owners of old old diesels use a quart in a 100g to help out with the newest "fuel".

The "fuel" today DEPENDS 100% on the local deliverer to add the additives that claim to stop excessive wear from the product.

It's time for another adjustment to your meds FF.**

First, your statement that viscosity has almost nothing to do with lubricating qualities is so far from the mark that I now question even the very limited knowledge that I previously gave you credit for. That statement proves once and for all that you havent a clue what you are talking about. It has long been obvious that you have no background or fundamental knowledge of marine engineering subjects but lately your comments seem to indicate a diminishing capacity for anything other than rabid political diatribe. Maybe you should stick to rabble rousing and leave technical issues to others.

Diesel fuel lubricity additives (if and when required) are added either at the refinery, or at the terminals if they*receive their supply through a pipeline also used to*transport jet fuel. The local deliverer doesnt have anything to do with it. Overdosing your diesel fuel with some redneck version of magic sauce is contaminating it - period.

Your education in fuels and lube oils (as well as most everything else) seems to have stopped in the 1950s FF, and your suggestions on these boating boards is beyond irresponsible and*now borders on the hazardous. You are certainly free to wreck your own machinery in any fashion you desire but, please, stop recommending your backwater remedies to the operators of post 1950 technologies.
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Old 07-03-2008, 11:06 AM   #11
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RE: L.O. Pressure

Don't know if this is relevant but a number of years ago our Range Rover developed a sticking lifter when the engine was cold. A good friend of ours is the head of the engineering department at one of the marine industry's most respected diesel*propulsion and generator manufacturers. When I mentioned the sticking lifter problem to him he suggested adding a quart of ATF to the oil and running it for an oil change interval, which for us is 3,000 miles. He said the sticking problem could be the result of a bit of dirt or buildup in the hydraulic lifter and the detergent quality of ATF might get rid of it.

It cured the problem but what I wanted to mention was that he cautioned me VERY strongly to use only ONE quart in the engine (which with the filter holds about 8 quarts of oil). The reason, he said, is that too much ATF will "thin out" the oil with the result that the lubrication will not be what it should be.

Here is a definition I found in a quick search on the internet: "Viscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or extensional stress. It is commonly perceived as "thickness", or resistance to flow. Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction."

This sure sounds like a definition of a fluid's lubrication qualities and attributes to me.

-- Edited by Marin at 12:08, 2008-07-03
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Old 07-03-2008, 06:43 PM   #12
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RE: L.O. Pressure

Lubricity and viscocity are different but both are essential.

Oil lubrication relies on a film of oil between surfaces (say between a rod bearing and a crank throw). It keeps the microscopically rough surfaces apart so that they don't actually touch and wear.

When there is pressure forcing the surfaces together (compression stroke), the oil film is forced out. If it flows out too quickly, the film is lost and the surfaces lose their lubrication.

Viscosity determines the flow rate. If it's too low, the oil flows out too quickly when pressure is applied and you lose lubrication.

So:

When ATF is added to engine oil, you decrease viscosity but don't much affect lubricity. As Ken stated, don't run it real hard, and as Marin stated, keep it under 15 to 20% concentration.

As far as the fuel lubricity goes, supplementing is probably a good idea when your fuel dock goes to low or ultra low sulphur fuel. In 1994, when OTR diesel went to low sulphur, lots of us were faced with injector pump overhauls within a few months. The rebuilt pumps were supposed to have improved parts to handle the low sulphur fuel, and they seem to have held up.

In WA, at least, the red dyed fuel still seems to be high sulphur, but who knows for how long.
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Old 07-03-2008, 08:07 PM   #13
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RE: L.O. Pressure

Chris---

Thanks for your clear explanation of viscosity and lubricity. Very helpful to know.
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Old 07-03-2008, 08:10 PM   #14
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RE: L.O. Pressure

Thanks again Guys.
For the last 40 years (now retired and doing consulting work) I have been at sea as an Engineer on Tankers, crude oil and product.
The last 25 as Chief Engineer, in that time I spent many years as C/E on a couple of product tankers carting product from our refinery in Brisbane up and down the Australian Coast.
We produced the product and then carried /supplied it to all the different oil companies.
Caltex (producer) to Shell, BP , Mobil etc.
As with the lubes and the diesel each end user modified their own product on receipt before resale.

I have also recently begun to suffer the leaking injector pump. At present living with it until I return South and then I will have to renew all the seals in the pump.

I have stayed away from detergent type oils due to their clensing properties and the end results with older engines. But the use of ATF in small quanties at low load and when the engine is warm is worth the possible positive result.

Will let you know if I it all goes welll when I return to the boat and try it all out

Benn
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Old 07-04-2008, 04:50 AM   #15
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RE: L.O. Pressure

Rod or crank bearings are lubed by the pumping action of the space between the surfaces changing (compressing the oil) , riding on the film..

The can lobes are lubed by the oil film with no help.

The cylinder walls are lubed by the film left after the oil scraper ring leaves the right thickness of oil on the slight scratches from honing .

The oil viscosity is usually the measure at an elevated (operating) temp , and those that change the oil HOT know that even 40wt CF2 is as thin as sewing machine oil at that temp.

The ATF is far better in sheer strength , so any slight loss of oil pressure from the rods or mains , will still not result in metal to metal contact.
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Old 07-09-2008, 09:15 AM   #16
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RE: L.O. Pressure

"I have stayed away from detergent type oils ..."

I just reread your post and noticed this statement ... are you saying you have been using a non-detergent lube oil in your diesel?

If this is the case, that may be the reason you are having this problem. Detergents and the dispersants that live with them keep the soot in suspension so it can be removed by the filter and also neutralize acids which in combination with the soot make sludge.

Pull a rocker cover or if you can see the rockers through an oil fill cap, look to see if they are clean or coated with crud.*If you have been using non-detergent oil for a long time you probably have all the lube oil passages coated with this same crud and it is causing a restriction in flow and that*may be*the reason for the high pressure until the oil thins out.

These are little high-speed engines, they require a completely different lube oil than medium or slow speed engines and non-detergent oils are not at all suitable.

As for FF's suggestion to use ATF, consider the source. His last post shows a shuddering ignorance of how bearings work. A 5 minute course on tribology would teach him more than he has learned about engines since the 1950's.
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Old 07-10-2008, 09:07 PM   #17
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RE: L.O. Pressure

Wear*= Contact + Load + Motion (Caterpillar Service Training). The oil film on a crankshaft journal eliminates any wear- in a perfect world. Increase load, motion or contact and you get a proportional amount of wear.
Steve
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