pcv valve

Submitted: Thursday, Jul 03, 2003 at 19:47
ThreadID: 5796 Views:13392 Replies:8 FollowUps:1
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has any body heard of a faulty pcv? valve being the cause of excess oil consumption in a 1hz diesel. apparently they should be set at 33 degrees open. any info would be appreciated.
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Reply By: Martyn (WA) - Thursday, Jul 03, 2003 at 20:37

Thursday, Jul 03, 2003 at 20:37
See if this is of any use to you it's not specific to the 1HZ motor more of a general thing, I found it in an engine tips forum I'm a part of. From what I understand yes it could cause excessive oil consumption, but I would think you would see smoke, how much oil are you consuming, what's excessive? Can't help with the angle setting I'm not familiar with this, I thought that these valves where on petrol motors I've never seen mention of one on a diesel before, I could well be looking in the wrong place, maybe the Nissan motor is a tad more agricultural, the way I like it.....

The PCV Valve

by George Staley

When an engine is running, a tiny amount of the exploded gas-air mixture forces its way past the piston rings in a condition known as blow-by. These fumes would build up pressure in the crankcase and cause trouble if they were not allowed to escape. On old cars, a hollow pipe led from the top back of the engine and carried the fumes down under the car. This “draft tube” prevented gasses from building up in the engine but it also allowed the oily fumes to escape into the atmosphere.

Modern cars have many types of pollution control devices to protect the quality of our air. The system used to control crankcase fumes is called Positive Crankcase Ventilation or PCV. In this system, the “draft tube” leading from the crankcase is not vented to the ground but is routed to the intake manifold where the oily fumes are sucked into the engine along with the gas-air mixture and burned.

Most PCV systems enter the manifold below the carburetor. If this system is added to an older car, it is vital that a PCV valve be placed into the line carrying fumes from the crankcase. The function of the PCV valve is to regulate the flow of crankcase gasses as well as to prevent a “backfire” from the manifold, which could cause an explosion to travel down into the crankcase. The vacuum of the engine regulates the opening in the PCV valve. When engine vacuum is high, the flow of gasses is low. When engine vacuum is low as in rapid acceleration, the flow of crankcase gas is greatest.

Some systems use a dual setup in which the blow-by gas is sent to the air cleaner case as well as the intake manifold. When the dual system is used, it is common for the tube to the air cleaner to originate at a tappet cover or from the oil filler cap.

It is important that the size of the PCV valve be appropriate for the flow of fumes. PCV valves do come in many sizes so some research may be necessary to find the best after-market valve. The parts supplier may know the suitable size or he may be able to seek advice from the manufacturer.

It is important that you do not seal off the crankcase completely as a build up of fumes could cause engine problems.
Keep the shiny side up
AnswerID: 24127

Reply By: Steve from Drive Systems Victoria - Thursday, Jul 03, 2003 at 21:26

Thursday, Jul 03, 2003 at 21:26
Was not aware that the 1HZ had a PCV, but rather a breather line hose from rocker cover to intake ducting. Oil consumption can be increased if the crankcase becomes pressurised and cannot vent off by whatever means. A pressurised crankcase will force oil mist up the cylinder walls and the extra oil can be a problem to piston rings to sweep away. Oil can pass the rings, helped by the pressure, and then be burnt in the combustion chamber and possibly not be even noticed. You have to investigate why the crankcase is not venting.
AnswerID: 24135

Reply By: Phil R - Thursday, Jul 03, 2003 at 21:45

Thursday, Jul 03, 2003 at 21:45
Just had look at mine and can't see any PCV valve, pipe comes out of the rocker
cover on right hand side then does a right turn towards the front where it enters
the air intake via a hose.... unless there's something in the rocker cover ???.

AnswerID: 24139

Reply By: Member - DOZER- Thursday, Jul 03, 2003 at 21:55

Thursday, Jul 03, 2003 at 21:55
I think you are mixing up the PCV valve and the tappet cover flutes, that seperate oil from crankcase fumes. I know there was a recall on the 1hdt factory turbo motor to adjust these flutes in the tappet cover. A novel idea is to make up a collector of the oil that gets in to the tube either buy buying a pneumatic water trap or putting two tubes into a sealed bottle, one low one high, and then to see how much you catch...
Andrew wheredayathinkwer mike?
AnswerID: 24142

Reply By: Phil R - Thursday, Jul 03, 2003 at 22:18

Thursday, Jul 03, 2003 at 22:18
I remember the PCV valves on the old holden red motors etc, a small spring loaded check valve on top of the rocker cover and the hose went to the inlet
manifold to suck the fumes in for burning. I don't think the 1HZ has got one, I
looked in the Toyota engine manual and it is mentioned at the front of the book
but I'm yet to find it further in, the book also covers 1PZ & 1HD-T's

AnswerID: 24149

Follow Up By: scott - Thursday, Jul 03, 2003 at 22:23

Thursday, Jul 03, 2003 at 22:23
phil i was told it was under the rocker cover . toyota apparently had problems withn the early 80 series like mine
FollowupID: 16247

Reply By: Billowaggi - Thursday, Jul 03, 2003 at 22:52

Thursday, Jul 03, 2003 at 22:52
No inlet manifold vaccume on diesel engines, therefore no PCV valve ,only on petrol engines, what you are talking about is a crancase blowby oil separator.
Regards Ken.
AnswerID: 24154

Reply By: Phil R - Thursday, Jul 03, 2003 at 22:53

Thursday, Jul 03, 2003 at 22:53
Hi Scott
I checked through the book again but I'm unable to find anything on the PCV under
the rocker cover or anywhere else, is your 1hz turbo'ed ???, it does mention oil
usage due to faulty turbo seals. just a thought.
AnswerID: 24155

Reply By: herkman - Friday, Jul 04, 2003 at 06:37

Friday, Jul 04, 2003 at 06:37
Yes a faulty PCV can raise oil consumption.

However sometimes before you plonk down your money, you can bring them back by soaking them in petrol overnight.

Worth a try, give it a good flush out with kero before re installing


Col Tigwell
AnswerID: 24167

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