1999 V70XC...95k miles...I've had code 4801 (catalytic convertor failure) for months...had it in to three different shops - none of them seem convinced the cat is bad. Physical inspection reveals no rattling/etc. Performance and mileage seem fine. Car runs like a dream.

Recently, I've also noticed a pretty substantial oil leak coming out of the (i think) small hole in the oil filler spout. The oil settles in the valve cover, under the plastic cover. I know it is coming out of the hole in the filler spout, because there is oil around the little ledge on the oil filler...which is ABOVE the plastic valve cover.

So, 2 questions. One, my crankcase pressure is obviously too high - something is up with that...any suggestions?

And question 2, could this be the source of my cat code? Could that high pressure somehow be affecting the exhaust system so that my o2 sensors are being tricked into thinking the cat is bad?

I don't want to drop $1k on a cat, only to find out the code remains. I have a hunch the two are related...

Love to hear any comments,

dave

 

Make sure all hoses for the Vent system are Clear. Make sure the Vent box is also clear.
I would make sure all routine maintance is all up to date and Vent system cleaned out and take it from there.

 

Thanks for the reply...you are talking about the pvc system - the box located under the intake manifold? I've read some ideas about cleaning the system out...wondering what your thoughts are vs. simply replacing the whole system. Groton sells it for just over $100 plus the intake manifold gasket. It looks like a pretty straightforward job. Interestingly, i've also noticed an intermittent lifter noise - which is new. A few posts seem to associate this with high crank pressures.

Do you have any comment on whether this might be causing my cat code faults? I'm praying that fixing the crank overpressure will turn off the cel and I can return the $850 cat.

Dave

 

Yes I am talking about the PCV system.
Yes the Box is under the Intake.
If you remove the Dipstick and blow compressed air into it and it comes out of the oil Cap then the system is for the most part working.
One of the small elbows or the Vaccum tree on the intake might be clogged.

Are all the O2 sensors within specs?

 

i've had it scanned at least six times...never pulled any o2 sensor codes. i'm taking it in to the volvo dealer tomorrow to have them work out the oil trap issue...i'm just too busy to tackle it right now. I'm keeping my fingers crossed that for some odd reason, this is causing the cat code.

thanks so much for your help!

dave

 

No problem it might be causing I have seen funnier things happen.

 

I am having a similar issue with false catalytic coverter message code 4801 coming on my 2001 V70. Checked for exhaust leaks and found nothing.
I also am other leaks though. Power steering reservoir leaking, replaced 2 hose clamps and added power steering stop leak but looked under car today and leaks remain. Any ideas?

 

Yours could also be bad injectors.

 

Im just a newbie in automech but heres my idea.

The catalytic converter is a part of your exhaust system.As for the oil leak that relates to a mechanical or sealing problem with your engine. If it is an internal leak it would make your cat. go bad. To many hydrocarbons in the cat. cover all the chemical plates in the cat and cause it to heat up and possibly do more damage.otherwise check out parts.com they have a good auto parts information and see how much it really cost if your changing damage parts.

 

Sorry to bump this thread but did you ever get to the bottom of this? As I'm having the exact same problem but a bit more as the pressure has blown a blanking plate out of the engine at the back

 

It is very well known that clogged Volvo PCV systems will cause cat failure codes. Replace the PCV system including all hoses (do not waste you time trying to clean things).

Most of the time this will solve that issue.

However, EVAP system leaks will also cause cat failure codes, as well as vacuum leaks.

And "Drifter28" over thought it.