6s (V6) PCV Valve Failure, Excessive Oil Consumpti - Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum
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post #1 of 355 (permalink) Old 11-15-2005, 02:09 PM Thread Starter
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This CRP is specifically for the Mazda 6s (V6) platform.

PCV
The PCV (Positive Crankcase Ventilation) Valve is a check valve that allows excess exhaust fumes in the crank case to re-enter the intake manifold and be re-combusted for emissions sake.


Problem:
If the valve breaks (its basically plastic), one of two things can happen,
http://forum.mazda6tech.com/viewtopic.php?p=36503#36503

1: The valve gets stuck close. Pressure builds up in the crankcase, eventually finding an outlet. This usually results in oil spraying back up into the intake tract, or blowing the dipstick out of its holder.

2: The valve gets stuck open. When vaccuum is applied (application of throttle), the intake air sucks the oil out of the crankcase using the pcv hose as a large straw.


Problem 2:
If option 2 occurs, a low oil condition can occur, which has an extremely high likelyhood of spinning a bearing. This can result in just a rod bearing replacement, or a complete bottom end rebuild. ($$$ and Very Bad)


Identifying The Problem:
Weekly oil checks will reveal a sudden increase in oil consumption. Sometimes blue smoke exiting the exhaust can be indicative of oil being sucked into the intake tract of the engine (and being burned in the combustion chamber).


Solutions:
There is no "concrete" solution at this time. The only thing that can be done is preventative maintance.

1. Check your oil level at least bi-weekly or weekly. It only takes a few seconds. Pop the hood before leaving in the morning (weekends are great for this) and just check the dipstick. Oil level should be between the top 0 and the ford logo on the dipstick.

2. Inspect the PCV valve every oil change (5-7.5k miles). Below is instructions on how to do so. Easiest method would be removing the hose from the rear of the manifold, and applying pressure/vaccuum to test for resistance.

3/ Purchase a second PCV valve and run it in-line with the current valve (on the same hose). This will provide a level of redundancy. If one of the valves should fail, the car will still be ok.


PCV VALVE INSPECTION [AJ]



NOTE:
Removing the PCV valve might damage to the tab of the PCV valve and it will not be able to be reinstalled. Due to this, inspect the PCV valve with it installed on the vehicle.

1. Disconnect the negative battery cable.
2. Disconnect the PCV hose from the PCV valve.
3. Apply pressure to the PCV valve and verify that there is no airflow.
If there is airflow, replace the PCV valve.
4. Apply vacuum to the PCV valve and verify that there is airflow.
If there is no airflow, replace the PCV valve.



#1 is the valve for anyone wondering.

Replacement valves are available from forum sponsors and online mazda parts sites for around 10-12 dollars.
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post #2 of 355 (permalink) Old 11-15-2005, 02:36 PM
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*goes to check oil*

Aw crap, its low... though I've not noticed any smoking.

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post #3 of 355 (permalink) Old 11-21-2005, 05:19 PM
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post #4 of 355 (permalink) Old 11-22-2005, 11:03 PM
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that valve is a real PITA to get to eh?

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post #5 of 355 (permalink) Old 11-22-2005, 11:11 PM
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Quote:
Originally posted by Toadster@Nov 22 2005, 10:03 PM
that valve is a real PITA to get to eh?
[snapback]563101[/snapback]
Not really, visible by peering off to the driver's side shoulder of the upper intake manifold. Taking off the upper intake will make it a piece of cake if you can't get to it as is for some reason.

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post #6 of 355 (permalink) Old 11-22-2005, 11:16 PM
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Quote:
Originally posted by mmarfan@Nov 21 2005, 01:19 PM
Yea I'm ALWAYS 1 quart low every oil change... I'm at 32000 miles... can I get a new motor out of this...
[snapback]562201[/snapback]
Not unless your engine fails... and for those after their warranties it would be a VERY good idea to constantly keep an eye on this.

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post #7 of 355 (permalink) Old 11-22-2005, 11:20 PM
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Quote:
Originally posted by Mazda_Gremlyn@Nov 22 2005, 10:16 PM
Not unless your engine fails... and for those after their warranties it would be a VERY good idea to constantly keep an eye on this.
[snapback]563108[/snapback]
Or not, then it becomes a really good idea to buy a Duratec 3.5L

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post #8 of 355 (permalink) Old 11-27-2005, 10:55 AM Thread Starter
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84fordman posted a how-to on 6tech for this problem. Here's the forum link till I get a chance to turn it into an article on monday.

http://forum.mazda6tech.com/viewtopic.php?t=4271
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post #9 of 355 (permalink) Old 12-31-2005, 02:32 PM
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That has to be it, that HAS to be the reason for my engine troubles, The oil was alwasy low and i was always adding a quart and a half, and i have experienced the problem when they replaced it the last time, this is very interesting, a cheap replacement part is most likley the cause of the 2 engines i went through in a matter of months. how would you run a second valve in line with the first?

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post #10 of 355 (permalink) Old 12-31-2005, 02:40 PM
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Quote:
how would you run a second valve in line with the first?
[/b]
Click the link in the post just above your own.

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