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KNOCK, KNOCK, WHAT'S THERE?
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Old 11 Jun 2014, 05:07 PM   #1 (permalink)
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KNOCK, KNOCK, WHAT'S THERE?

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Quote:
Originally Posted by beejay820
Descriptions of piston slap vary so much; knocks, taps, ticks, etc, so I don't know whether my knock is I've got a slapper or not.
My '98 Type R has a momentary, deep, knock at cold start up only. The noise, which almost sounds like big end knock, lasts for just a second or two and there's no further sign of it until really cold start up again.
I've had a good 10w/40w oil put in, which made no difference and the oil pressure seems good.

Please could someone put me out of my misery, is it piston slap? Or do I need to get the begging bowl out again?

================================================== =====

I posted the above a few weeks back, since when I've had the car looked at by a couple of pretty knowledgeable guys and discussed the problem with many others without reaching any concrete conclusion.
The engine has been flushed and Fuchs 15w/50 oil added, but the knocking has progressively worsened. The consensus is that the brief knocking sounds like a crank noise caused by momentary oil starvation, but why the oil isn't there immediately is a mystery.
Fingers are being pointed at the oil pump, why though when the pressure is up to 6 bar when cold, makes little sense either.

The engine was completely rebuilt less than 8000 miles ago, so it all seems a bit strange. Has anyone experienced anything similar or know of any possible oil pump problem which could cause my knock.
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Old 11 Jun 2014, 06:02 PM   #2 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

Im not being nasty or anything but Tidgy already replied to your original post on the 09/01/14 stating
"without hearing its hard to tell, could get a specialist to have a listen and see what they think. I use scoobyclinic myself, in fact picking my car up again in sat lol"
IS MINE A SLAPPER? << this jumps to Tidgy's reply.
then you replied to it.

What you need to do is take it to Subaru specialist to check it out not a high street garage or make a video and move the camera around different locations of the engine bay slowly and post it on youtube and then post your link to the video on this forum that may help the experts answer your question.
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Old 17 Jun 2014, 01:14 AM   #3 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

I don't understand why you have felt it necessary to get on your high horse. I was just asking fellow Subaru owners if anyone has experienced anything similar.

It's allright saying get it seen to by a specialist like Scoobyclinic, but there's not one near me and if I could find the time to get to, say Scoobyclinic, I would have to wait around for several hours while the engine cooled down so the noise would possibly be evident.

I think your suggestion of making a video holds merit and I have actually attempted this this evening, but, I assume because the ambient temperature was relatively high, the knocking was not that loud. So I will have to try again when it's cooler.

Thank you anyway for your reply.
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Old 17 Jun 2014, 01:31 PM   #4 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

as it only happens at start up I wouldnt worry, I say this as bottom end knock isnt just at start up, it tends to be "there" from 2550 to 3100 rpms,

you could get a solid bar(socket extension bar) or screwdriver that the blade carries thru the handle and have a listen for knocks to locate the noise,
Get some else to start and stop the car quickly while it is cold and move the said bar across the engine to locate the source when you first start it, the knock will obviously be louder the closer you are to it.

There may be some new app for it but Im old skool.
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Old 17 Jun 2014, 09:42 PM   #5 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

Quote:
Originally Posted by bugeye_bob View Post
as it only happens at start up I wouldnt worry, I say this as bottom end knock isnt just at start up, it tends to be "there" from 2550 to 3100 rpms,

you could get a solid bar(socket extension bar) or screwdriver that the blade carries thru the handle and have a listen for knocks to locate the noise,
Get some else to start and stop the car quickly while it is cold and move the said bar across the engine to locate the source when you first start it, the knock will obviously be louder the closer you are to it.

There may be some new app for it but Im old skool.
Thank you for your reply Bob.
What you say about bottom end knocks being audible at mid revs, particularly when the engine is hot has always been my experience and everyone who's listened can't detect anything once the engine is running.

Sharing the knock is made difficult because it only happens very briefly and at initial start-up. Even if switched off immediately, it doesn't do it again.
Usually it does it after being standing for a few hours, but here's an odd thing; if the outside temperature it warm, the knock is much lighter and shorter. Thinner oil, maybe??
I had 3 oil changes in a very short time and I'm now running 15w/50, possibly I should go down to a 5w/50.
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Old 18 Jun 2014, 07:41 AM   #6 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

how long does it take for the oil warning light to go out when you start it from the temp it knocks ?
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Old 18 Jun 2014, 05:10 PM   #7 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

Hi again Bob,

I don't have an oil light, just a pressure gauge. (It's electronic, so I assume it's connected to the oil pressure sensor??)
The knock is immediately before the gauge whips up to 6 bar. It's almost as if there's no oil somewhere until the pump pressurises. Once it's there, it stays around for a while when the engine isn't in use, but gradually drains away.

Once the engine is hot, the gauge says the pressure maximum is around 4 bar, at 3000rpm it shows 2.5 to 3 bar and tickover is around 0.5bar. I don't know what "normal" oil pressure for a Type R should be, but the pump obviously works. Is there any sort of non-return valve which keeps the oil in the ways? ............no, that's silly!
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Old 18 Jun 2014, 07:29 PM   #8 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

why no oil pressure light ?
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Old 19 Jun 2014, 12:17 AM   #9 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

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Originally Posted by bugeye_bob View Post
why no oil pressure light ?
I assume the oil pressure gauge uses the sensor connection, but I don't really know. With it having a different instrument binacle to the WRX, I don't actually know where it should be.
I looked for a workshop manual for the type R and can't find one.
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Old 19 Jun 2014, 07:49 AM   #10 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

The light is the same on all impreza`s so shouldnt take much finding,
Maybe all the crappy sensors etc are the problem?
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Old 20 Jun 2014, 12:59 AM   #11 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

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Originally Posted by bugeye_bob View Post
The light is the same on all impreza`s so shouldnt take much finding,
Maybe all the crappy sensors etc are the problem?
I certainly don't have an oil can lighting up on my dash, but I can't see it causing the knocking.
I'm off on holiday next week, so the knock can wait.
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Old 20 Jun 2014, 08:49 AM   #12 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

but if they have extended the pipes etc for the oil new pressure sensor (your original cant do the job on the gauge as its either on or off) then is the oil having to travel around those new sensor lines when it should be pumping oil around your engine for a fraction of a second, which may explain your knock,
Id be tempted to find out "why" the OE doesnt work as it can be kept either in it`s original position or moved to a bung above no3 pot if you reuse the original hole for the new gauge sensor.
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Old 28 Jun 2014, 08:04 PM   #13 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

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Originally Posted by bugeye_bob View Post
but if they have extended the pipes etc for the oil new pressure sensor (your original cant do the job on the gauge as its either on or off) then is the oil having to travel around those new sensor lines when it should be pumping oil around your engine for a fraction of a second, which may explain your knock,
Id be tempted to find out "why" the OE doesnt work as it can be kept either in it`s original position or moved to a bung above no3 pot if you reuse the original hole for the new gauge sensor.
Hi Bob, I've just got back from a week's holiday. Thank you for your advice, I will have to investigate what has been done previously.
I'll let you know what I find.
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Old 07 Jul 2014, 09:11 PM   #14 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

Quote:
Originally Posted by bugeye_bob View Post
but if they have extended the pipes etc for the oil new pressure sensor (your original cant do the job on the gauge as its either on or off) then is the oil having to travel around those new sensor lines when it should be pumping oil around your engine for a fraction of a second, which may explain your knock,
Id be tempted to find out "why" the OE doesnt work as it can be kept either in it`s original position or moved to a bung above no3 pot if you reuse the original hole for the new gauge sensor.
Hi again Bob. I've found what I assume is the oil pressure sender, under the alternator, just in front of the EJ20 stamp. I've taken a photo and as you can see, there is a spare spade connector next to the sender, which I can only presume is the oil light feed.
I also have a oil temp gauge in the car, which has never worked, where should that be connected to?
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Old 07 Jul 2014, 10:53 PM   #15 (permalink)
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Re: KNOCK, KNOCK, WHAT'S THERE?

the standard sender can be dropped in the bung under the intercooler(I dont like the T pipes) and extend the wiring, that will give the dash the signal again.
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