pcv valve

This is a mystery, and I'm unsure how many variables are involved. For example, does cold weather operation make it worse or no effect?

I've never had a vac gage on my Prius so will take your word for it. I do know that on my 2000 GMC Sierra it had fairly high vacuum unless you were heavy into the throttle. Is the Prius vacuum response more to do with the VVT or the Atkinson??

Speaking of throttle, on that GMC the deposits in the IAC/TB were a black sludgy stuff, especially on the IAC pintle valve. That was what caused the start-stall problems on a lot of the Vortec motors, and poor idle characteristics

So I'm guessing it was oil from the PCV that caused the deposits in my GM truck, which were not nearly as bad after the TSB called for replacing the PCV with a new valve that had a restricter oriface

I checked the "puddle" in my Prius again, it does appear somewhat liquid, so it couldn't be oil. When the aromatics are allowed to vaporise from gasoline, what is left behind looks sort of what like is sitting in the puddle in the intake

 

OK, if the puddle is gasoline and not oil, then it is coming from the intake valves. I've attached an excerpt from the 2001 NCF. Pages 71 and 72 show intake valve timing under a variety of operating conditions.

Maybe those owners who have a puddle operate their vehicles so that intake valve timing is advanced more of the time, thus intake and exhaust valves have overlap and the intake gases come back up to condense in the intake manifold. This happens under medium load conditions as well as low to medium speed with heavy load (ranges 3 and 4 in the graphic.) Note that ranges 2 and 5 have retarded valve timing where the blowback does not occur.

How about the black gunk that forms on the throttle body interior and throttle plate? Is that a separate phenomenon? Its interesting that this gunk does not make the gasoline puddle dark.

 

Patrick

Makes sense, as my Prius has lived the vast majority of its life in city driving under medium varied load

I also have that gunk on the underside of the throttle plate, and the bore a bit past the throttle plate. It's not sludgey like the stuff that would build up in the IAC and TB of my 2000 GMC Sierra 5.3 V8. More of a blackish stuff.

That's probably oil, no?

jay

 

Hi Jay,

You might be right...I previously thought the black gunk was exhaust gas residue released by the intake valves. However if it was, then you'd think the puddle would be darkened since we've recently concluded that the puddle comes via the intake valves.

 

IIRC Bob Wilson previously suggested some of the air intake puddle might be derived from gasoline 'derivatives'.

I was suprised to find it still accumulating slowly in 2001 Prius after adopting engine oil 'underfill' policy.

Perhaps it is turning over rapidly. When some accumulates, the engine inhales it during the next full airflow event. If so, it would not acquire butterfly soot.

 

wouldn't cleaning the PCVhoses with brake Kleen or gasoline would degrease the oils inside, however, deteriorate and crack the hoses over time (internally too!). Wouldn't it be easier to order a new PCV valve with hoses along with it? Or the hoses are expensive too?

Anyone know the parts number?

 

Hi Phil,

When I replaced the PCV valve on my 2001, I used brake parts cleaner to spray out the interior of the PCV hoses. One hose was quite dirty while the other was pretty clean. The hoses looked OK to me so I did not replace them; however there's no harm in replacing them if you feel like doing so.

Since brake parts cleaner is intended to be sprayed upon rubber brake parts (like the rear drum brake wheel cylinder seals or the flexible brake hoses) I would not be concerned about its effect on the PCV hoses.

 

just changed mine today, thanks for all the help!

 

It looks like I got my pcv valve replaced at almost 70K on my 2005 Prius. According to the invoice:

Air Filter Dirty
3810 Replaced Air Filter/PCV Valve
336 CPT $26.70
1 12204-21011 Valve Sub-Assy, Vent $8.64 (PCV valve)
1 17801-21040 Element Sub-Assy, AI $18.00 (air filter)

Parts: $26.64
Labor: $26.70
Other: $0.00

Total: $53.34

The hourly labor cost at my dealer is about $80, so I guess it took the tech about 20 min to replace both air filter and PCV valve.

 

S&I, getting to the PCV in 20 min, and putting the car back together again, sounds like world record time to me. Did they return the old PCV valve to you as "proof"?

 

No, they didn't. Are you wondering if they indeed did the job? I normally don't ask for proof of work that they say they have done.

They did some other work (like oil change, tire rotation, etc.) at the same time, so perhaps the tech just divided the total hours by the number of work items.

 

Tried this job tonight, I started a little after 6PM and finished about 8;45PM. Biggest problem right in the beginning, removing wiper arms. They will not move by normal physical effort, I think the shafts are tapered so they wedge themselves to fit tight. Finally I hit upon the solution (that I had forgotten). Insert a large screwdriver under pivot point of the wiper, put the non-decorative nut on the shaft about 1/2 way to total length. ( at least 2-3 threads ) then gently tap the nut with a medium size hammer and at the same time try to wedge up on the screwdriver. Gently, as all the leverage points are flimsy materials and easy to break. The nut is threaded on to save the threads, It is the hammer that does the trick, not the screwdriver. I ended up not even installing the new PCV valve as the original seemed to work better than the new one. So Ill save the new one for an emergency.

 

I know an easier way to pull the wiper arms. Loosen the nut a few turns then lift the arm to the upright position and wiggle the arm at right angles to the hinge, they come loose in a few seconds.

 

Thanks, I hope I remember that next time.

 

It's easier to pull the intake and move the main engine wiring harness, IMHO. Clean MAF and throttle body while you are at it. Might as well do spark plugs too. Anywhere from 1-2 hours for most DIY types.

 

Seilerts: Are you still speaking of replacing the PCV valve, if so, can you clarify how pulling the intake would give you access to the PCV? OH, The intake being under the throttle body. Are all hardware accessible to remove the TB?

 

Sorry, I should have been more specific. The black plastic air box that contains the air cleaner + MAF and attaches to the TB. Pull this, then you can complete loosen the main engine wiring harness, and access the the PCV.

 

^^ Wonderful suggestion. I took apart the cowl and *still* had to struggle to access the PCV valve.

 

That is how I did it. Changed the spark plugs while I had that stuff apart.

 

Great, This sounds definitely better than the windshield wiper route, it never hurts to also to clean the TB and MAF anyway. Thanks much. Andy.