I have been so busy the last week. With the Holidays coming I should have some down time and be able to dig out the old pump.
By the way here is a post on facebook claiming by that same guy claiming to have rebuilt an ebay HPFP.

 

4 pumps, it tells me the problem is not the pump. Something is damaging it, I would replace the in-tank fuel filter, and if necessary wash the fuel tank.

 

So if Im understanding correctly, as oil warms up, it expands and it pushes the spring and diagram, so excess oil volume is stored in the temperature valve while hot.

 

Yes, that is correct. This is why BMW came up with the measuring tool. Their tool measures the location of the diaphragm and thus acts as a "dipstick" to determine oil loss. When the oil is cold the distance should be less than 26mm. However mine was bad at 24mm and a new OEM pump measures 19mm. People on this thread were already theorizing that oil loss was the problem with these pumps and BMW's NewTis and the measuring tool are proof of that. However, pumps can fail for other reasons too.

 

** REPAIRED**
I found a series of YTube Videos, where it is explained how this pump operates, main failure modes (Surprisingly Orings are not a common failure) , how to disassemble the pump, clean, repair, oil fill, OIL TYPE, closing, test and install. the HPFP.
I thought it will be more complicated.The only PROBLEM is that the videos are in Portuguese, VIDEO could be translated by somebody in the forum directly on YouTube, in the CCaption option.I speak spanish so I understood a bit of the explanations. Here is the link to one of its videos you will need to see all. His user name is Mr2tempos

This guy has successfully repaired many MINI HPFPs , he explains and even shows cut pumps to understand its functionality.

step by step assembly and disassembly.

I just opened mine
It's important to mention, that my pump does not leak oil, if your's does, chances are that your diaphragm is broken and it is not repairable.

 

Those videos explain what most of us thought. Oil loss stops the proper pump function. Seems like this guy has figured out a repeatable method of how to refill the oil to the proper level after cleaning the pump. The latest post says someone used 20w40 Yamaha motorcycle oil with good results.

 

First , Thank you for staring this thread, I'm not willing to pay 1k USd for a new pump at the dealer, when I can see repair kits for all other brands for $50.00 usd.

My pump does NOT leak oil, but still it is failing, so there could be many reasons for fail. If your pump is leaking oil through the diaphragm, that is not repairable, you will need to get a used pump to use the body. As you can see in the photos I uploaded, my pump is full with oil, black oil with a strong smell, doesn't look good, its really runny. The youtube guy, Mr2tempos, recommends to use a mix of 30/70 ATX oil mixed with W90 oil. There's someone on the video commenting that he succesfully used Yamaha moto oil, but it makes sense to use thicker oil to compensate for the wear on the pistons. My car is a 2009 MCS with ONLY 40K miles.
I followed all steps in the video, but used 5w30 oil, my bad, my pump didn't work, video clearly states that you may need to follow procedure a couple of times, not losing oil while re-closing is crucial. I will try again with the 30/70 mix and will post my results.

Here is a translation of the procedure: This is a translation from Youtube instructions, follow at your own risk.

Step 1

Remove the 3 screws which retain the cover

Drain all oil, remove* pistons and springs and wash with gasoline. (*) they easily slide out.

Clean Cylinders with a cloth, do not use gasoline here, as it will be very difficult to get it out.

Dry everything.

Step 2
Fill the cylinders with SAE W90 oil up to the top, slowly re-insert springs and pistons in its place, push pistons with your fingers several times, until you can feel some pressure has been built.
Repeat this step at least 4 times on each piston. (See video)

Step 3 Fill with oil the remaining of the pump cavity. (see video)
Oil the pump cover with same oil until the internal bearing is lubricated.
SLOWLY place the pump cover back over the pistons, avoid abrupt movements. Place the 3 screws and tighten them uniformly and slowly to avoid excessive oil loss.
Finally clean pump and re-install in your car. (see video)
Important There are no spare parts for this pump. If your components show too much wear, you should recover another pump. Even with some wear, W90 oil will compensate for it. Not all pumps will be ok with this procedure, nor you will succeed at the first try, You ll need to try again, step by step until you succeed.

 

Brand new OEM pumps can be had from third party suppliers with a lifetime warranty for around $540 USD.

True but oil can leak internally and be passed into the gasoline stream or into the engine. In any case we do know that oil loss will cause the pump to fail. My pump was completely dry on the outside, yet it had enough oil loss to cause malfunction.

I think the proper way to fix oil loss on these pumps is to use what I believe is the factory injection port. To add oil using the injection port does not require any disassembly of the pump but a special fitting will have to be made to fit the port. Once connected to the port, a hand operated hydraulic pump can be used to inject the precise quantity of oil needed. You will know when you have added enough oil by measuring the location of the diaphragm which according to my brand new pump, should be 19mm.

When I have some spare time, I will try this on my old pump but I might not get this done for weeks or even months so if anyone else wants to brave this experiment.... go for it!

Thank you Myfast for sharing your photos and knowledge gained from your teardown. Very interesting indeed. Hopefully we can figure this out and find a reliable way to fix our pumps rather than shelling out big bucks.

 

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a) I was tempted to buy one of those pumps, but didn't felt assured that they are really OEM, nor if the warranty will be for real, I may be wrong.
b) Its true that oil may leak internally, but if that was the case, the oil would be diluted in gasoline, thus losing all of its lubrication properties, therefore the rotating cam would weld to the pistons due to excessive friction and heat.(See photo)
Refilling with oil in this scenario will not solve the problem as the leak would continue.
c) when refilling with oil it is critical to eliminate as much air as possible from inside the cylinder.

Top rigth you could see a GOOD rotating cam and piston, in first plane you can see a friction-welded cam and piston head.

As the piston welded to the cam, the main shaft simply broke. This is the side that mechanically connects the pump to the engine's camshaft.
Photo credits Mr2tempos

 

Which way the oil will leak depends on pressures. On the low fuel pressure side of the pump the fuel is at about 70 psi and if the internal oil pressure of the pump is higher, then the oil will only ever flow from the pump into gasoline and not the other way around. But another leakage path is from the pump directly into the engine via the camshaft drive side where there is essentially zero pressure so a very easy leak path.

It took 10 years and 100,000 kms for my oil to leak down to the point of the pump starting to malfunction. So with a leak that slow, I would be ok re-injecting oil again in another 10 years.

If oil is injected without pump disassembly, then there is little chance for air to get inside. My working assumption is that when oil is injected at the factory, it becomes pressurized and maintains that pressure because the spring loaded diaphragm is pre-loaded. As oil leaks out, the pre-load disappears or lessens and causes the pump to malfunction.

But again there can be many modes of pump failure such as the welded example you have provided. My suggestion will only work if the sole reason for pump failure is loss of oil. If oil is somehow contaminated with gasoline, then all bets are off.

As far as warranty goes, many on this site recommend FCP Euro. I have no affiliation but they seem legit to me.

 

SUCCESS !! SUCCESS !! SUCCESS !!

I followed the maintenance procedure on my pump, my engine started at the first try (Temp aprox 50 F), I just let the electric pump work for 1 minute twice to purge any air in the piping, my car had 1 month sleeping.
The half engine CODE is no longer present, on the test drive the car ran perfectly as if nothing ever happened, I stopped at a gas station and it started back with no problem, I drove for 15 minutes on normal to middle/high demand, no issues. Returned home, restarted the engine, no problem.
I used the 30/70 oil mix, and follow the steps described in my previous post, credit to Mr2tempos, with the only difference than on this, my second try, I vacuumed the cylinders to make sure that there is oil ONLY inside, as air is compressible and this would reduce the pump efficiency. (SEE PHOTOS) After filling and closing I measured the diaphragm, it had 15 mm depth, I was afraid oil will have not enough space to expand once it gets hot, so I loosen the 3 screws without removing them, until driping started, I let 10 drops out, retightened screws and measured 20mm, now I fill safe.
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For those like me, that didn't understand the operation principle of this pump, I'll try to explain:
With the help of the pistons, this system pushes oil into an expandable cylinder (EC) made of corrugated steel, this EC is located within a larger cylinder which contains the gasoline, when EC expands due to oil pressure, it pushes gasoline to the engine. Oil and gasoline are on independent circuits, so they never mix.

Happily a normal syringe perfectly and tightly fits in to the cylinder. I filled cylinders with oil to a 50% level and then inserted the syringes and applied vacuum, I hold vaccum for 24 hours, I used a piece of garden hose with a longitudinal cut to maintain position. You will see oil and air bubbles slowly getting into the syringe.

After 24 hours I removed the garden hoses, do not push the rods, let the expandable cylinder, now compressed due to vaccum, expand, thus pulling the oil in the syringe and filling all its cavities with oil, no air. Then I removed syringes and follow procedure as per Mr2tempos videos.
After assembly, the pump felt a bit heavier to turn manually, that is a good indicator that there is no air inside the cylinders, this is good.

Finally, I want to take back all I said inside my head about the MINI brand during this past month hahaha!

 

Congratulations on your success! I like the way you figured out how to purge all the air from the pump. Very clever. I think that is the key and I personally don't think that the type of oil is all that critical as long as it is not too thin or thick and has good anti-wear properties. Any good quality hydraulic oil should work IMHO. Can you post pictures of the expandable cylinder? I am still trying to wrap my head around how that works. Also please keep us posted on the long-term results of this rebuild. It is really good that we are now applying hard data to this problem, and measurements of the position of the diaphragm within the thermal compensator are vital. To re-cap what we know: BMW says anything less than 26 mm is good, but my pump failed at 24mm and my new OEM pump measured at 19mm and works like a charm. Myfast, your rebuild pump measured at 20 mm and works great. So when refilling your pumps shoot for 19-20 mm.

 

Torquehead check out the videos mentioned above by
Mr2tempos on YouTube and use the cc and translate to English. You will get a great overview of the whole pump. As many of us expected it’s very simple mechanically and now that we understand how it works it makes sense that the fix for most pumps is relatively simple. I’m going to attempt to clean and restore my original pump. I’m glad I didn’t toss it. It will be nice to have a spare hanging around since there are 3 n14 minis in my family. Now all I need is some time .

 

This is the Expandable cylinder 'EC' in a cut view taken from Mr2tempos videos. Sorry the image says EP, should say EC (Expandable cylinder).

So the failure modes could be:
a) Broken diaphgram , causing oil leak outside (non repairable, I didnt see a way to detach the diaphgram)
b) Internal oil leak, not sure how or where this could happen without being catastrophic, as either a gasoline/oil mix or no-oil, would cause the pistons to friction-weld to the cam.
c) Wear in pistons, changing oil to a thicker one, to compensate (most common failure mode)
d) There should be a check valve somewhere inside, if failed, gasoline would return to tank, so no high pressure could be built or maintained.
e) what else????

 

Thanks Myfast. That is so weird and so complicated. Why not just have the piston press on the gasoline directly? Why the expandable cylinder which I would think should suffer from metal fatigue eventually. When you had yours apart, could you remove the expandable cylinder? Can you remove the piston?

In regards to failure modes, we know from other posters that oil can leak externally and typically leaks from the thermal compensator and I have to agree it looks like a non-replaceable part. I have to disagree that internal oil leakage would always lead to welding unless the pump was run dangerously low on oil. So I think the most likely mode of failure is a very slow internal leakage.

If the diaphragm seal blew out, and all or most of the oil escaped then I can certainly see welding taking place fairly quickly.

 

I finally did watch most of Mr2Tempos's videos. Man I wish we had them fully translated. I tried translating what seemed like important parts but I got some confusing result in regards to the operation of the expanded cylinder. He seems to say that gasoline goes through the holes in the cylinder. If anyone is fluent in Portugese, a concise summary of pump operation according to Mr2tempos would be greatly appreciated.

I see how he develops internal oil pressure which would preload the diaphragm. He does this by overfilling the pump and then assembling it. The large o-ring prevents oil from escaping during assembly but he does not verify correct preload by measurement which we know is 19-20mm.

I see o-rings at the base of each cylinder and I believe there are o rings used on the drive shaft as well so there are at least two internal leakage paths. I also noted that the oil seems to be thicker than regular hydraulic oil. It looks more like a gear oil.

I saved my old pump too and am planning to dig into it when I get the chance. Like you, finding the time can be a challenge.

 

** I do not see how could a new or repaired temperature valve compensator with its internal diaphragm could be welded.

 

** Please share your findings. Good luck

 

Hey Myfast,

Thanks for the info!

You may be correct that one of the failure modes is a breakdown of the oil’s ability to lubricate over a very long lifespan with the result being excessive wear. The volume of oil is quite small and is highly stressed, thus I think your theory has merit.

But let’s not forget that BMW has designed, built and has for sale a tool for measuring loss of oil.

The BMW TIS that covers use of this tool states: “When the special oil now escapes due to leakage and this causes the impairment to the function of high-pressure pump, any lack of oil in the high-pressure pump can be checked at the temperature compensator.”

So clearly, loss of oil remains as one fairly well-know failure mode as identified by BMW. One possible internal leakage path is from the swash plate to the engine via the main drive shaft. This leakage path would have nothing to do with the gasoline side of the pump.

Please let me clarify my comment on welding. What I meant was that if the diaphragm blows, then all of the oil will leak out quickly and shortly thereafter, due to a total lack of lubrication, the friction from heat will cause the pistons to weld themselves onto the swash plate. I did not intend to suggest welding can be used to repair anything on this pump. Sorry for the confusion. Hope this is clear now.

I fully understand how the thermal compensator functions and again I guess I was not clear in what I said. We both agree that it allows expansion of oil as the oil heats up. BMW tells us that for the pump to operate correctly, the diaphragm has to be a certain distance from the outside of the compensator.

If you re-assemble the pump with too little oil, then there will be no load on the spring that pushes on the diaphragm. This is what I refer to as the “pre-load” and we have determined that a diaphragm distance of 19-20 mm provides the proper pre-load. As the oil expands when it gets hot, this distance gets smaller because the diaphragm is pushed back and the spring is compressed more.

If the diaphragm measurement is 19mm on a new pump when it is at room temperature, and then 100,000 kms later it measures 30mm at room temperature, this means the pump has lost a lot of oil. And from the BMW TIS we know loss of oil causes “impairment of the function of the pump”.

The spring on the thermal compensator is constantly pushing on the diaphragm which is exerting a force on the oil, possibly 5 or 10 PSI. As the oil leaks out and the spring moves forward, the oil pressure will drop because the spring can no longer push as hard as when it was compressed. When the diaphragm has travelled as far as it can, the oil pressure can drop to zero. I believe some oil pressure is necessary at all times in order for this pump to be properly lubricated and this could be when internal, unintentional welding occurs resulting in catastrophic failure as shown by some examples from Mr2Tempos.

 

** I m totally in line with you.

 

Update on my repair.

After some days of enjoying my repaired pump, I started to struggle a bit on the first-morning start, instead of going live at first try it is taking just a couple of tries, also I ve started noticing a small stumble upon mid-hard acceleration.
Thinking and thinking my guess is that oil maybe too thick, I used 70% W90 mixed with 30% hydraulic transmission oil, MY BAD! After practicing my poor Portuguese watching Mr2tempos video again, he uses de inverse mix, 30% W90 with 70% hydraulic. So I wanted to try this, corrected-mix, but thinking that the root cause is piston wear I look and found a video from Project Farm , Im not lying, I was totally SKEPTICAL, he uses an oil additive to restore engine compression, results were amazing, investigated a little more and I found several more videos showing the same positive results, so I went ahead and removed the pump again, it takes me now 14 minutes to do so, I prepared a mix 30% W90 with 70% hydraulic, to that, I added 40% of engine RESTORE. It contains microscopic particles of silver, copper, and lead, which are meant to fill worn cylinder surfaces, seriously, watch de VIDEO.
After reassembling the pump and reinstalling it, which now takes me a ridiculously short time, the car started at first try, no codes, no stumble on heavy acceleration.
I know that I had reached this point before, where the pump was Ok and then started to slowly lose performance so, I will keep you guys updated if Engine RESTORE helped to keep full performance.

 

Myfast, did the last fix last? So, i had a try the first time yday. It lasted just one ride, now code is back and car has trouble running. I did use some hydraulic oil at home tho, did not measure diapgrahm. Is oil rly that important? Im getting w90 tmrw and some good hydraulic oil to have a proper mix. About diapgrahm, when do i need to measure it? If i understand correct, when i fill the pump with oil, measurements has to be 19-20 after? My diapgrahm is intact, pump had black oil in it. I just did 100k km and pump started to fail in my car. Dealer quotes me 500 for it, so if i can repair and maybe just prolong this purchase a bit, would be great. Its expensive

 

Hi Boris,
When you remove your pump, measure and record the diaphragm distance. You will probably find it to be 25-30mm. After you have refilled the pump with oil it should be 19 to 20mm. Good luck and keep us posted on your results.
Tom

 

So, from the tip of the seal inside to cover outside, if i understand correctly, should be 19,20? If i press too hard, that "seal" in diapgrahm can break correct, so i need to tread lightly right? Sure, i'll keep u posted. Just wonder how long did fix last if anyone else attempted it. Im working tmrw, saturday im going in again. Hopefully it will be a success.

 

Measure straight in the hole (perpendicular to the outside face of thermal compensator until you touch the diaphragm. But here is the catch; you need to measure from the bottom of the circular indentation in the centre of the outside face of the compensator. Since this indentation is about 8 or 10 mm in diameter, your caliper won't be able to reference from that surface since it cannot fit. Just measure from the flat outside surface and then subtract the depth of the indentation and you will then hopefully arrive at the correct measurement of 19-20mm if you managed to get the right quantity of oil into the pump.

Measurements should always be with a light touch but in this case, I don't think there is much danger of moving the diaphragm since there is oil behind it preventing it from moving.