APR HPFP piston seal went fuzzy.

Today, I went to shorten the hpfp studs because they are just a bit too long for those reoccurring cam follower swaps. I cut 6mm from them(the end that goes into the tensioner cover), chamfered the cut end, and made sure the threads were clear and worked again. I made a stud driver using a M6x1 coupling nut( https://mobileimages.lowes.com/product/converted/008236/008236750614lg.jpg ) and a M6x1 bolt - 10mm long. Threaded the bolt into the coupling nut and installed the newly cut studs.

I then decided to just take a look at the hpfp piston. I checked for play within the piston collar...and was tight. I slid out the piston and noticed the rubber seal inside was a bit off. It looked to be coming apart with slivers of rubber along the inner opening. At this point I decided to remove the flat rubber seal and give it a closer look. Got it out and there were a few slivers of rubber that I saw measuring 3mm to 4mm long barely hanging onto the inner race of the seal.

Luckily, I found an o-ring sized 8.8mm I.D. to 12.6mm O.D. in my metric o-ring set seeming to be an close replica in size to the flat seal. It fit back into the 'piston holder groove' perfectly. The piston went back perfectly. A test run of about 20 miles went perfectly. But, I still hope APR will send me another seal, or two (as I imagine there are actually more than the one...one at each end), but I can only ask and see if they will help out here when I ask them on Monday to "send a new seals to me". Doubt it, but going to try as I do not know how long the o-ring will last...and this seems to be a much easier solution to the problem than sending them my hpfp for inspection, which they would likely reject as I have touched it.

Refer to Post #10 for exact seal to use...

Tricky situation.. I hope you can get that seal from APR but I have a feeling they will tell you to buy a new pump.
Does your oil have a strong fuel smell?

Finder said:

Tricky situation.. I hope you can get that seal from APR but I have a feeling they will tell you to buy a new pump.
Does your oil have a strong fuel smell?

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Nope, no fuel in the oil. Nothing came out when I removed the piston as well...so, the inner seal must be OK.

APR said exactly what I expected..."we do not sell the seal separately from our rebuild kit" which also isn't sold without them rebuilding an hpfp. However, I was told the o-ring should be fine as it is just a preliminary oil seal.

So, was lucky to have that 8.8mm I.D. to 12.6mm O.D.. I still have concerns of its longevity. I guess I just need to keep an eye on it, or even better to just add a new one, every time I swap over cam followers. I do have 17 left in the O-ring kit...LOL :thumbsup:

ROH ECHT said:

Nope, no fuel in the oil. Nothing came out when I removed the piston as well...so, the inner seal must be OK.

APR said exactly what I expected..."we do not sell the seal separately from our rebuild kit" which also isn't sold without them rebuilding an hpfp. However, I was told the o-ring should be fine as it is just a preliminary oil seal.

So, was lucky to have that 8.8mm I.D. to 12.6mm O.D.. I still have concerns of its longevity. I guess I just need to keep an eye on it, or even better to just add a new one, every time I swap over cam followers. I do have 17 left in the O-ring kit...LOL :thumbsup:

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See if IE will sell you a seal. The seal that came with my kit was spring energized and seemed like OE quality. They indicate on their site that their piston is the same diameter as APR's.

I called IE and Ben told me they are custom made and although the ID may be the same, the OD and height/thickness may be different...and they do not sell them separately. I think for now, just going to trust the o-ring I installed. I have brakes @ $1000 coming up before I can do another $1200 on a new HPFP plus upgrade and then injectors.

Get the IE pump kit when you have the funds.

Was thinking of doing so.
I have 84k miles on this APR.
All the GIAC guys/employees use Autotech, but my first Autotech lasted less than 5800 miles due to my Tech reinstalling the used follower when he rebuilt my hpfp during the K04 install. Others with Autotech are doing OK as well, I just shy away from it since I didn't get to fully experience it when thinking I had 10k miles before needing to check the 1st CF.

I rebuilt my 100k mile pump with IE internals and it has been perfect for 10k miles. I just inspected the follower and it was in great shape at 10k, didn’t even put the new one in. There’s no reason I won’t be getting 25k per follower, same as with the stock pump.

We'll see...got to decide early next year while keeping a close eye on that o-ring fix.

APR confirmed the seal material today, it's "Flouroelastomer Polymer"

I have added more I have found out after doing more measuring and ring seal reading...I mean, a ton of reading. Especially Chapter 5: https://www.parker.com/literature/O-Ring Division Literature/ORD 5700 Parker_O-Ring_Handbook.pdf

...so, if needed; use VITON 75D quad-ring: https://www.amazon.com/Sterling-Sea...d=1510820276&sr=1-11&keywords=viton+quad-ring

Size-012 Quad-Ring dimensions; sec;1.78 ID;9.25 OD;12.81

This is a 2.5tfsi by APR, but it's the best image and angle showing the seal I speak of and where it goes...seal #1 goes inside position #2:

i need to change my damage tip of apr hpfp

do i need to touch the seal and replace it or i can change the tip directly without need to touch the internal

kakluote said:

i need to change my damage tip of apr hpfp

do i need to touch the seal and replace it or i can change the tip directly without need to touch the internal

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You should only need to slide the piston out part way to get the spring out of the way to get at the end with the spring retainer bits.

Thanks for doing all the work on this, I ordered some as I have 2 APR pumps.

I just happened to be there...trimming down the studs of the stud kit you generously donated....and, as always, curious. Thanks again to you.
I receive the quad-rings this week...and I will post the fitment findings then. I calipered the #3LL out of the original before ordering, and I believed to be spot on with my choice after comparing dimensions to the size chart for quad-rings...but will know for certain at the end of the week when I have the pump off.