Oil Pump/Filter Pressure Relief Valve

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AustHaflinger
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Oil Pump/Filter Pressure Relief Valve

Post by AustHaflinger »

Most modern vehicles have a pressure relief valve fitted in the engine lubrication system that allows the engine oil to continue to circulate if the oil filter gets blocked.

Does the Haflinger have this?? If so where is it.

See pic below
Image

In the pic you can see the brass T junction between the oil filter and the dizzy with the oil pressure switch on top of it. In the base of this where the oil pipe casting that joins the oil pump to the base of the oil filter there is a vertical spring controlled valve/plunger. When the engine starts and the oil pump gets up to pressure, the pressure lifts the plunger and allows oil pressure into the chamber above it (where the brass fitting screws into) to operate the oil pressure switch and in the case of my vehicle oil pressure to the oil pressure gauge. There does not seem to be any other purpose to this pressure valve.

The problem is that when the engine is turned off (or in theory oil pressure lost) the valved closes but pressure seems to remain in the chamber above the spring controlled valve/plunger so that it may take quite a few minutes for the oil pressure light to come on and while you can see pressure dropping on the gauge it also takes a couple of minutes for pressure to fall to zero.

The ramification being that when driving and oil pressure is lost, I do not have immediate indication that oil pressure has been lost.

So does this spring operated valve just allow oil pressure to the oil pressure switch or is there an additional reason for this. If just to provide oil pressure to the switch, then really the valve is not really required.

Advice appreciated.

Cheers

Garry
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kerry460
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Re: Oil Pump/Filter Pressure Relief Valve

Post by kerry460 »

Gary
i certainly would not remove it .
there are two of these "mushroom"valves .
the one you have mentioned uses a spring 8.5 mm dia x 45 mm long

the other mushroom valve is in the bottom of the oil pump cover plate
this one uses a spring 7.5 mm dia x 50 mm long

both seats are meant to be re faced when rebuilding an engine .
it a a flat faced cutter inside an alignment tube .
after cutting the face , the mushroom valve is placed in a rod and lightly tapped with a hammer to finish the re seating .

i hope this helps as the springs can be transposed ,

kerry
ex Tasmanian Haflinger agent .
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AustHaflinger
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Re: Oil Pump/Filter Pressure Relief Valve

Post by AustHaflinger »

Hi Kerry - certainly not intending to remove it. I am aware of the valve under the oil pump and now that you have mentioned it I assume it is the pressure relief valve if the filter gets blocked.

So what is the purpose of the valve under the oil pressure switch certainly it is not needed if it is just related to the oil pressure switch so must be there for another reason.

Cheers

Garry
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Re: Oil Pump/Filter Pressure Relief Valve

Post by kerry460 »

the honest answer , i cant remember ,
sorry .

kerry
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Re: Oil Pump/Filter Pressure Relief Valve

Post by heinkeljb »

Gary,

I have never seen a sectional drawing of either the oil pump or the oil filter system, or a diagram showing the oil route through the engine. So can't be certain of anything.

My "assumption" was that the spring and ball valve under the oil pressure switch had two galleries which it controlled oil passage to. One would be blocked off when oil pressure increased as engine starts running. If oil pressure is lost, the spring pushes the ball down and closes off the gallery going to the oil filter and opens the one that bypasses the oil filter.

Problem with this "assumption" is that the ball bearing can only seal "one" hole when pushed closed by the spring, so maybe what it does is allow oil when at high pressure to force the ball off the seat, allowing it to go round the filter, but at the same time allow oil to bypass the filter. When the oil pressure falls, the ball is pushed against the seat, blocking the oil passage to the filter, but leaving the bypass passage still open.

With out taking an oil pump apart and the filter case apart, I am guessing just like you. I have a spare oil filter section attached to a crank case. If i get time and the weather is kind enough to let me take it off, I will have a look at how it works.

I have also noticed that oil pressure on the gauge goes down once you turn off and it takes a while to get to the point the oil light comes on - one of the main reason why I wanted an oil pressure gauge! :shock:

John
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AustHaflinger
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Re: Oil Pump/Filter Pressure Relief Valve

Post by AustHaflinger »

Hi John - I follow your logic. There is no ball bearing in the system, it is a metal fixture like an inverted mushroom. The V of the mushroom head fits into a machined section in the oil gallery of the same shape making a seal. The stalk of the mushroom fits up inside the spring and oil pressure pushes the head of the mushroom up opening the orifice and when pressure falls the spring closed the head like you describe.

As we have found, the pressure in the upper chamber stays high after oil pressure has dropped off giving false readings to the oil pressure light and any aftermarket gauge.

Of course the oil pressure light should come on immediately the engine stops but it doesn't - has always been the case with my Haffie.

I might try a different oil pressure sensor and see if it makes a difference.

Garry
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Re: Oil Pump/Filter Pressure Relief Valve

Post by heinkeljb »

Gary,

Blind leading the blind again!

Oil pressure valve is the one on the oil pump.
Oil bypass valve is the one fitted under the oil pressure switch.

How it provides this "bypass" function, I don't know. The repair manual states that if it is leaking it provides unfiltered oil to the parts that need lubricating. That would mean that when it is open it is allowing oil to bypass the oil filter. Therefore it must remain shut at all times and only when there is a difference in pressure on the top side with the spring will it open to make a hole which allows oil to flow through the hole and hence "bypass" the oil filter.
The oil pressure switch (and your gauge) must be registering the oil pressure on the lower pressure side of the oil filter. I.E. the side after oil has been pushed through the oil filter(?)

High oil pressure (both the gauge and the switch can't both be wrong at the same time can they?) after you turn the engine off, must be because the oil is not able to escape from the system. Oil is pushed through the main bearings, big ends and out into the sump. That suggests that what ever holes there are that the oil uses to escape are either blocked or the clearances are too small(?) This of course, can be skewed by oil viscosity - to thick and oil pressure too high, to thin and oil pressure too low.

Hopefully, some one on here can explain the path of the oil round the engine.

John
Last edited by heinkeljb on Sun Mar 01, 2015 8:07 am, edited 1 time in total.
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Re: Oil Pump/Filter Pressure Relief Valve

Post by Goatwerks »

If the filter plugs or restricts, the filter bypass valve prevents oil starvation to lubrication circuits.
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Re: Oil Pump/Filter Pressure Relief Valve

Post by heinkeljb »

Now that we know the bypass valve under the oil pressure switch only controls whether oil goes into the filter or not depending on the oil pressure difference above and below the mushroom valve.

Under ideal circumstances, the spring pressure on the mushroom valve keeps it presses against its seat so that all the oil goes through the oil filter.
Under adverse conditions, such as the filter being blocked by metal filings or oil gum, the pressure below the mushroom valve overcomes the spring opening up a hole through which oil can flow, thus by passing the oil filter. This oil has the down side of not being filtered and could potentially do damage to other items like, Main bearings or big ends, but at least oil is being feed to them.

:idea: Got that part! :geek:

Now we come to the next part in the quest for knowledge. :ugeek:

What does the other mushroom valve in the oil pump do?
How does it achieve it?

Oil is "sucked" up via the "tea strainer" in the sump towards the oil pump. The "tea strainer" is the course filter which stops the oil pick up from being blocked by large debris in the sump, where that would come from without causing the engine to stop working / start making a very audible noise I don't know!
Where in the oil pump does the inlet from the oil pick up pipe go?
Does it go straight in to the cogs section to be pushed out via the valve?
Does it go in the cog section via the mushroom valve and the spring providing the control of the pressure of oil getting into the cog part of the pump? This seems daft, as the cogs are going to increase the pressure of the oil leaving the chamber irrespective of the pressure coming in!

Still looks like I will have to take the oil pump off an engine to find out.

John
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Re: Oil Pump/Filter Pressure Relief Valve

Post by Goatwerks »

Auto shop 101,in simple terms, it prevents lube drain back keeping the oil filter(primed) full for the most part ;)

Side note: Not all Haflinger engines have the oil pressure switch in the same location, some are located on the case (top)in front of the left side tin work.
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Re: Oil Pump/Filter Pressure Relief Valve

Post by heinkeljb »

Auto shop 101 does not relate to anything on a Haflinger. :?

Nice to know that the mushroom valve in the oil pump just keeps the oil in the oil filter and does not let it back into the sump. No mention of that in the repair manual, or the operators handbook.

I have seen the oil pressure switch up near the oil cooler - obviously tapping into an oil gallery going to or from the oil cooler.

So now we know what the two valves in the oil system do.

Jim,

Do you know in which order the oil goes through the following after leaving the oil pump,
the oil filter,
the oil cooler,
the main bearings,
the big ends?

I am trying to understand how the oil circulates round the engine as it is not described anywhere in the documentation that I have ever seen.

John
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Re: Oil Pump/Filter Pressure Relief Valve

Post by AustHaflinger »

All very interesting discussion - I am not sure I follow it all and certainly doesn't offer an explanation of why pressure remains in the chamber under the oil pressure switch.

Maybe this chamber has direct access to the oil filter so the drain down valve stopping oil draining out the oil filter keeps pressure up under the oil pressure switch.

I think I need to have a look at a lubrication diagram to see what is happening.

The issue remains though - when the engine is turned off or on a bad day the engine oil pressure drops it may take a few minutes for dash indications show up - too late - dead engine.

Can other owners with series 2 engines check that when they turn off their engines, the oil pressure light comes on immediately or is delayed for a couple of minutes.

Cheers

Garry
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Re: Oil Pump/Filter Pressure Relief Valve

Post by heinkeljb »

Gary,

My engine, which I believe is a late factory replacement one as it has no "official" engine number on it and was put in in the 1980's also suffers from slow return to zero on the oil pressure gauge.

I have never seen a diagram depicting the oil route through a Haflinger engine, maybe there is one for the Steyr-Puch 500 / 650TR / Invacar type engines which are similar.

Pressure loss from where the oil light switch / pressure gauge on you engine (and mine even though I am using a "sandwich plate" adapter) would have to be by oil either returning to the oil pump and back into the sump, but that is what the mushroom valve in the oil pump is there to stop.
That means the oil must leak to the sump in the other direction. That is via the main bearings / big ends / and however the cylinder heads get their oil.

Does it make any difference to the speed at which your light comes on (when you stall the engine - you need power to on still to make the light work. I think mine turns the power off to the oil pressure switch when you turn the ignition off), if the engine is cold or if the engine is hot?
I will have to try this next time I drive Lurch.
If there is a difference then it could be down to oil thickness.

John
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Re: Oil Pump/Filter Pressure Relief Valve

Post by Julian B »

heinkeljb wrote:I have never seen a sectional drawing of either the oil pump or the oil filter system, or a diagram showing the oil route through the engine. So can't be certain of anything.
I don't have one either, but I do have a very large original poster in my workshop which shows a cutaway drawing of the engine. Terrible lighting conditions to take a photo, but these might help ...

Julian
Attachments
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Re: Oil Pump/Filter Pressure Relief Valve

Post by AustHaflinger »

When I turn the engine on, oil pressure comes up immediately and the light goes out immediately. When switching off, turning the ignition back on shows the oil light takes quite a few minutes for the light to go out.

As I indicated my concern is when driving along at 3-4000rpm and you loose oil pressure (rapid loss of oil or just low oil level) you will not know about it until the engine self destructs - on all my other vehicles that I have owned the oil light would come on immediately.

Garry
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Re: Oil Pump/Filter Pressure Relief Valve

Post by Goatwerks »

Normal operation. Try changing the switch before over thinking.
The only way the pressure would fall rapidly after shut down is worn bearings................................
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Re: Oil Pump/Filter Pressure Relief Valve

Post by AustHaflinger »

Yes Jim you are quite correct and that is what I intend to do.

However I recently had an incidence of low oil pressure where the light did not come on and I only picked it up when I glanced at the gauge - just trying to understand how the system works.

EDIT: What pressure oil pressure light switch to get - at road revs the oil pressure is about 60-70psi and at idle is about 40-50psi. As it takes a while for the light to come on when oil pressure is lost I guess I need something that comes on at a higher pressure - say 30psi. While I want to oil pressure light to come on earlier than it does I do not want it set so high that it comes on at idle on a hot day.

Any suggestions?

Cheers

Garry
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Re: Oil Pump/Filter Pressure Relief Valve

Post by heinkeljb »

Having now spoken to a man that rebuilt several of these engines / modified several to big bore (I think his current big bore is 850cc) engine. I have found out the following:-

The mushroom valve in the oil pump is the one that controls to oil pressure in the engine. It opens to allow high pressure oil back in to the sump via the lower hollow cog in the oil pump. Therefore if you have low oil pressure in the system it could be that the valve is stuck open. Other reasons would obviously be worn bearing, oil leaks etc.
High oil pressure would probably be the valve not opening I.E. sticking closed because either the mushroom valve has stuck in the bore, or the spring is full of muck and can not compress properly or for some other probably obvious reason.

So Gary,

It sounds like your momentary drop in oil pressure which your gauge showed, but your oil pressure light did not was because some bit of grit or something got stuck in the mushroom valve sealing face and allowed it to "bleed" some oil pressure out of the system and the pressure never went down below what your oil pressure switch works at. You would need a calibrated system to find out what pressure you current switch works at. I wouldn't rely on what might be stamped on it after 40 years.

The repair manual states that idle pressure for both mark 1 and mark 2 oil pumps at their lowest should be 14.5psi (1 Atm) and for the the mark 3 (latest) oil pump should be 21.3psi (1.5Atm) - That would mean you want an oil pressure switch which make the electrical contact at ~ 1 Atm minimum.

John
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Re: Oil Pump/Filter Pressure Relief Valve

Post by AustHaflinger »

My low oil pressure was caused by low oil level in the engine. :o

I had a friend with a 96 Toyota Corolla and he used to drive it until the oil pressure light came on (he thought it was the oil level light) and then put oil in it. Not such an issue if you shut the engine down at the time but all too late in a Haffie.
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Re: Oil Pump/Filter Pressure Relief Valve

Post by Yakov »

Sorry if this question hijacks the thread topic a little, but... what is one to do if one needs the mushroom valves recut? I understand there's supposed to be a special tool from SDP, but is there any other way to do it? Does anyone with such a special tool offer a service?
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