Oil Pump or Crank

Road-race engines and ancillaries - general discussion
Vtechnician
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Joined: February 10th, 2013, 10:55 am

Oil Pump or Crank

Post by Vtechnician »

Hi all,

Firstly Im delighted to be one of the new additions to this great forum! Sadly my first thread is regarding an issue that has cropped up since my bottom end rebuild. I’m hearing an unsettling noise from the oil pump in my 1996 Fiat Coupe 16v Turbo. See video below:

http://youtu.be/R_HnLPxtm8o

A few points:

1) In the video the engine is running without any of the auxiliaries ie water pump, alternator, power steering pump and balance shafts.
2) The noise becomes prominent when the engine begins to warm up.
3) The noise disappears when the engine is revved .
4) When I probe the oil pump with a mechanics stethoscope I can’t pick up the noise.
5) I can’t find any loose metal plates, brackets etc.
6) I have removed the sump and drained the oil through a 400micron filter and found no deposits.
7) I have removed the oil pump and inspected the gears. I can see no signs of wear, cracking or cavitation. There’s no play in the gears and the pressure relief valve seems in good order.
8) The oil pressure when hot is 1 bar with 10w-60 mobil1. The crank was within spec when I measured it but just! Personally I think oil pressure is low for this viscosity of oil.

Does this noise warrant inspecting the crank/bearings? This is a last resort because I do not want to risk contaminating the bottom end but i think I've run out of options now.

Many thanks
Demetri
Guy Croft
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Re: Oil Pump or Crank

Post by Guy Croft »

Don't strip her down yet. Can anyone run a frequency spectrum analysis on this film? Maybe pick up the noise?

I don't have a wide enough analysis on my video system to tell.

I might be being too clever for my own good here but I think the frequency of the noise Demetri is referring to is too high for a 4 cylinder 4-stroke engine firing frequency at about 1000rpm engine speed (33Hz?)

My instinct suggests something in the belt array - cambelt or balance shaft belt and maybe a pulley rubbing or loose.

If it's the oil pump (meshing frequency) it can be deduced from the spectrum analysis.

Demetri - bar oil pressure hot at what speed? At idle I hope not under load!

If anyone can do a spectrum (as a film) I'd very much like to know.

G
Guy Croft, owner
Vtechnician
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Joined: February 10th, 2013, 10:55 am

Re: Oil Pump or Crank

Post by Vtechnician »

Hi Guy,

You could be onto something here! Im sure the timing belt had a little deviation from left to right when it was running but very minor. Perhaps its catching on a pulley. But the noise does sound like a metallic rattle/grinding noise.

The oil pressure at 1bar is at idle, also I am not running with balance shafts.

thanks
Demetri
Guy Croft
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Re: Oil Pump or Crank

Post by Guy Croft »

The frequency, I am pretty sure - is way too high for bearings. When I filter out the very high frequencies on my video player the crank and rod bearings sound normal. And the exhaust pulse. Very normal, rotation and no more than that.

Nothing wrong with 1 bar at idle, hot. There is no load on the engine. So long as it goes up to 4 bar when you rev up that is OK. 2.8 bar is the minimum hot under load and preferably more.

My acoustic filter seems to tell me that the noise is intermittent - albeit very high frequency - the kind of sound you'd get if a short part of the cambelt was of different texture than the rest. Or if the belt was rubbing on a belt cover that was vibrating and touching the belt intermittently. It seems to go 'noisy-quiet-noisy-quiet' at very high speed - if you follow. Maybe a whirring noise from a worn tensioner bearing.

There are only two things really that can generate high frequency noise at idle - the oil pump and the cam belt. Although the engine is only doing idle speed the cambelt velocity is extremely high. I guess one could work out the engagement frequency of the teeth, dunno how many teeth from memory but if it was 125 - then you have tooth-tooth engagement every revolution of the crank - at 1000rev/min that's pretty high..

By the way, there is a right and wrong way to set the tensioner on the 16v - see photos. If you have removed the right-side idler that sits on the old balance shaft bearing housing and runs against the belt you definitely need to put it back on or find another way to fit one! Because it you don't the belt will vibrate and rub on the belt guard in that region. And to be honest that was my first thought.

G
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Guy Croft, owner
Vtechnician
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Joined: February 10th, 2013, 10:55 am

Re: Oil Pump or Crank

Post by Vtechnician »

Hi Guy,

Thank you for the very comprehensive reply and detective work! I did replace the cambelt recently and unless I'm wishfully thinking Im sure this sound cropped up at around the same time. The tensioner is new and the idler bearing was replaced 10k miles ago. The tensioner was positioned as you've demonstrated in the "right" photo.

Ive just popped back from the garage with photos of the belt. Looks like it has been rubbing on a pulley! Its worn in 3 places on one half of the belt. See below:

I guess the next thing to do is replace the belt and ensure its running true and then maybe look at replacing the oil pump. I'll keep you updated with my progress.

Thanks again!
Demetri

Image

Image
Last edited by Vtechnician on February 22nd, 2013, 8:54 am, edited 1 time in total.
Urbancamo
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Re: Oil Pump or Crank

Post by Urbancamo »

That noise is definately not from the bearings. The noise characteristics are totally different.

http://www.youtube.com/watch?v=qJeB1096 ... e=youtu.be

Bit of effort and here's the Audacity provided spectrogram ectracted from MP3 sample. Bit of low frame rate due my steam powered PC but it works. Noise heard in this video seems to locate under 5 kHz region.
spectrogram.JPG
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Snapshot from the lower region of spectrogram where the noise seems to be. 3 noise pulses exist here. The gap between noise pulses is 0,20 to 0,25 seconds constantly thru the sample and the noise itself always last 0,25 seconds. Very little variation if any.

Hope these help!
GC_25
Guy Croft
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Re: Oil Pump or Crank

Post by Guy Croft »

Tommi

you are rapidly becoming one of 'my heroes'


GC
Guy Croft, owner
Vtechnician
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Re: Oil Pump or Crank

Post by Vtechnician »

Problem solved! Changing the timing belt to a Dayco brand did the trick! Seems like the Gates timing belt was a bad choice. There is a difference in the profile and texture of the teeth when comparing the belts.

Thanks for the point in the right direction Guy!

Demetri
Guy Croft
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Re: Oil Pump or Crank

Post by Guy Croft »

Demetri - with respect - Gates never get their productionbelt designs wrong - they - after all - pioneered the use of cambelts on engines.

I actually don't think the belt you were using is the right one for the 16v.

If my memory serves me correctly the 16v Int belt has air-vent slots in the teeth, see photo.

Can anyone remark as to whether I am correct or not?

Unfortunately I do not have a 16v Integrale belt in stock to examine,

G
Attachments
the rear belt is 16v Integrale I think, with venting slots in the teeth..
the rear belt is 16v Integrale I think, with venting slots in the teeth..
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Guy Croft, owner
Urbancamo
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Re: Oil Pump or Crank

Post by Urbancamo »

Demetri, can you gave your both Gates and Dayco belt numbers?

All my resources will say that Fiat/Lancia 16V engine will use the modern STDN 8M belt profile wich has slot under a tooth. Your old belt seems to be with STD 8M profile, wich is otherwise the same but without air vent slots under a tooth.
Both profiles are high-torque /long-life ones and designed to make very little if any noise at all when used in correct applications.

I think this topic verifies one thing - always carefully examine things like this before doing anything bigger.

T
GC_25
Vtechnician
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Re: Oil Pump or Crank

Post by Vtechnician »

Hi Guy, Urbancamo

The Gates belt doesnt have the groove in each tooth like the Dayco belt has (as you have shown in the photo). I need to double check with the my motor factor whether he supplied me the wrong part or whether this is the only profile Gates do for this application.

I'll get you some part numbers this evening!

thanks again
Demetri
Vtechnician
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Re: Oil Pump or Crank

Post by Vtechnician »

Ok the part number for the Gates belt is 5279XS and the Dayco belt is 173RHP180H.

Thanks
Demetri
Urbancamo
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Re: Oil Pump or Crank

Post by Urbancamo »

That's very strange because both belts are direct replacement to OEM or each other according to my sources.

I'm bit lost now if I'm honest...why Gates belt does not have clear slots under a teeth is really strange! But does it make any difference because otherwise the belts are identical.
Guy, what do you think?
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Vtechnician
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Re: Oil Pump or Crank

Post by Vtechnician »

I would expect the belt to whine a little but Im surprised it made such a noise; it sounded so metallic!
Will01
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Re: Oil Pump or Crank

Post by Will01 »

Hi Guys
I am hoping i can be of assistance.
First off the Dayco 173RHP180H belt is equivalent to the Gates 5279XS belt
To explain a little the Belt has 173 teeth with 8mm pitch and the 180 stands for 18mm width, so in that case the belts are similar

The Gates belt is what we would call a YM profile, this is the technical name that is referred to as in the Fiat Power Transmission profile specification standard.
Dayco refer to the same profile and name as their own RHP profile both the Dayco and Gates belts have profile which are approved to run on Fiat engines.

The difference you mention with the profiles where the Dayco has a dimple and the Gates has not has a long historical story, it is a common miss-conception that the dimple is their to reduce 'Noise'.
Originally when Gates held the patents on OE profiles the competition had to copy without infringing the profile patents, for some profiles Dayco would add the dimple to get past the patent, other competition took a different approach. Now you will find that Dayco have more or less adopted this profile design as it helps distinguish one of their belts.
There is a slight 'Noise' improvement using this dimple tooth in certain situations, however we find that the improvement is so low that the human ear cannot pick up the difference which is less than 1dB.

Originally on the Fiat engines Gates was OE so therefore you will find that the competition have tried to gain business in the Aftermarket using their own tooth design.

Now to help answer the question you have about a difference between the belts to give a 'Noise' improvement the best thing would be for me to have the two belts and i could compare to give a scientific reason for difference. But if i was to guess it could be that the rubber/fabric construction on the Dayco belt may be a little softer which would help reduce meshing 'noise' and also dampen span vibration.
The other thing is the Dayco belt may be a little different on centre distance length which may be changing the tension slightly that is on the drive which is also helping to reduce the 'noise'
If the Gates belt was 'noisy' and was tracking this could indicate a slightly higher tension on the belt (so maybe it is slightly shorter?) and the audible noise you heard was as you mentioned where the belt was wobbling into the pulley flange giving out a vibration of the flange.
If you have the old Gates belt still i would be interested to get this back and have a look, i could then provide a report on the belt that may help explain the noise?
GC_21
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