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Author Topic: Blowby Pressure???  (Read 3421 times)

November 03, 2016, 02:50:11 pm

thomas m

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Blowby Pressure???
« on: November 03, 2016, 02:50:11 pm »
I do get some blowby at 300,000 miles, but, in my judgement, after reading a lot of posts, not enough about which to be concerned.
A little smoke which increases as I rev the engine. I don't feel a lot of pressure if I cover the oil fill with my hand.

Is there any significance to the pressure in the valve cover? It's easy to measure by checking it at the breather outlet.
Are there any numbers for this???


Thomas, Original owner since new:
1991 MK2 Jetta Non-turbo 1.6 diesel, Engine Code ME, 5 speed 020 AWY 04120 transmission, Hydraulic Lifters,
320,000 miles
Location: Vancouver, WA
LOOKING FOR REBUILD OPTIONS IN PORTLAND, OR OR ON THE WEST COAST

Reply #1November 03, 2016, 06:13:47 pm

vanbcguy

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Re: Blowby Pressure???
« Reply #1 on: November 03, 2016, 06:13:47 pm »
There's no numbers no. What you are describing sounds pretty normal. More importantly, how well does the car start when cold? That's the real test of wear on an IDI diesel.

Sent from my XT1097 using Tapatalk

Bryn

1994 Jetta - AHU M-TDI - Jezebel Jetta
2004 Jetta Wagon - 1.8T - Blitzen

Reply #2November 03, 2016, 08:53:44 pm

air-cooled or diesel

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Re: Blowby Pressure???
« Reply #2 on: November 03, 2016, 08:53:44 pm »
the #s for this are called a compression test, a leak down test finishes off tests.

Reply #3November 05, 2016, 01:09:49 pm

thomas m

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Re: Blowby Pressure???
« Reply #3 on: November 05, 2016, 01:09:49 pm »
Hey Air Cooled or Diesel:

Since you are suggesting, why bother with a compression if a leak-down will be done anyway?
I've asked this in another posting. I can't come up with a good reason, but maybe that's due to
my ignorance of lack of engine building experience.

I'm just curious and that will lead me to do the compression test also. But, it seems that since
the leak-down tells me which cylinders are below par and isolates what the cause might be, the
compression test doesn't seem necessary.

Can you offer a constructive comment, please?

Thomas, Original owner since new:
1991 MK2 Jetta Non-turbo 1.6 diesel, Engine Code ME, 5 speed 020 AWY 04120 transmission, Hydraulic Lifters,
320,000 miles
Location: Vancouver, WA
LOOKING FOR REBUILD OPTIONS IN PORTLAND, OR OR ON THE WEST COAST

Reply #4November 05, 2016, 01:14:59 pm

air-cooled or diesel

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Re: Blowby Pressure???
« Reply #4 on: November 05, 2016, 01:14:59 pm »
im somewhat ignorant to the whole thing, as i have yet to do a leak-down test, as the equipment for me to do so runs like $400, i have a small compressor, so thats a start. everyone 1st requires a compression test, then if necessary a leak down test, the leak down test will cost you. a good compression tester for example runs about $70-$80. a compression test will tell you what you want at the sametime.

Reply #5November 05, 2016, 03:57:16 pm

thomas m

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Re: Blowby Pressure???
« Reply #5 on: November 05, 2016, 03:57:16 pm »
I'm no expert, just interested.

The compression test gauge is cheap and simple. Not (too) much voodoo involved.
On the other hand, the leak-down tester has a little art and a little technical involved in its design and use.

I built my own leak-down tester via Youtube from an old compression tester, a $5 regulator from Harbor Freight and some small section of 1/4 inch pipe fittings from Home Depot. Cost less than $10. I haven't use it yet. I also referred to this entry in Wikipedia:

https://en.wikipedia.org/wiki/Leak-down_tester

Not all have two gauges, not all have an orifice (calibrated leak), not all use high pressure; I guess you understand why if you are a fluid dynamics engineer !!!!! I'm not !!!
Thomas, Original owner since new:
1991 MK2 Jetta Non-turbo 1.6 diesel, Engine Code ME, 5 speed 020 AWY 04120 transmission, Hydraulic Lifters,
320,000 miles
Location: Vancouver, WA
LOOKING FOR REBUILD OPTIONS IN PORTLAND, OR OR ON THE WEST COAST