Hoses for 2006 M35 engine (VQ35DE)

[EniGmA1987]

So I was replacing my valve cover gaskets (again) and when taking off two of the hoses I saw one was craked on the side where it goes over the barb (I believe it is the PCV hose going to the engine), and another one snapped off completely at one of the barbs that connects between the two valve covers. It was extremely brittle According to my googling, it loks like this second hose of also PCV related, and is the PCV crossover. I am trying to buy some hose for replacement, but not really sure what specifications these hoses need to be. Unfortunately my infiniti dealer just closed down I see replacement on Z1 Motorsports, but they are silicone hoses that they say stay soft "forever". I know silicone has a very low PSI rating, and from looking at hoses it looks like most silicone in this range is only 5-10psi rated. So I am wondering, how much pressure is in the valve covers? I would assume more than 5psi, as I keep blowing gaskest over the years. I know compression fromthe cylinders is much higher than 5psi as well, but I dont know enough about engines to know if that pressure is the same up under the valve covers or not. I know the actual engine "air" isnt in the valve cover area as oil and such goes up there, but IDK if it has similarly high pressure or not or even what is normal pressure for them. For anyone wondering, I just drive hard when I drive this car, and hit high RPMs. So my valve covers keep blowing, usually in winter time.

So should I get the Z1 Motorsport hoses with 250 degree temp rating and risk blowing the hoses from pressure and having to do this all again? Or buy some other hoses rated for 95psi, but only 270 degrees? I think 270 *should* be high enough temperature...



https://www.z1motorsports.com/z1-produc ... -4284.html

[macgiver]

mac, I believe Positive Crankcase Ventilation (PCV) systems utilizing PCV valves in virtually all vehicles attemps to actually create a NEGATIVE pressure in the crankcase (yes-inside valve covers) to suck out "fumes" and routing them to burn in the combustion chambers on out the exhaust- for Emissions primarily and "basically" to help keep crankcase interior "cleaner" of blowby and deposits.We're talking a slight VACUUM here even - on average existing inside valve covers ,& lower case etc.

[ae7456t]

As luck (or lack thereof) would have it, I went through this exact problem 3 weeks ago when I was replacing valve cover gaskets on my '06 M35X.

I was able to reuse the PCV hose, but the hose between the 2 valve covers had turned to what felt like brittle plastic, and cracked when I was trying to get it off the barb.

Dejected, I went to my local Pep Boys to find a solution and stumbled upon "Dayco Fuel Hose, 7/16" x 2'".

https://www.pepboys.com/product/details/1127010/00830

I cut it to length, and carefully wiggled it on, and, so far, so good.

I don't recall if that is the same diameter for the PCV valve hose, and people smarter than me can probably tell me a better solution, but that length of hose did the trick to replace the connector between the two valve covers.

Good luck!

[EniGmA1987]

Thank you both for the replies.
Mac, that is good info to know. I started reading more on valve covers and PCV systems and all that since I made this thread and you are right they should have a negative vacuum for proper operation. I assumed positive pressure due to the name: positive crankcase ventilation. It would seem the only "poisitive" part of this is because it actively evacuates the pressure buildup.
That does have me wondering though, if I keep getting gasket leaks and oil is leaking out through the gasket, and I know this happens when I go too high on RPMs, is the PCV system simply innadequate for the stock engine when going above 6000 rpm? It would seem so to me given that I keep blowing gaskets ever since I have owned the car 9 years ago. Or is the reason for gasket failure not due to a positive pressure buildup from high RPM?




ae7456t, thank you for the link and sharing your experience on this. It has helped put me at ease quite a bit. I brought some hoses in to work today to measure on calipurs and the PCV crossover hose between valve covers is 7/8" OD x 5/8" ID. The Other hose sizes for the car are either 5/8" x 1/2", or 1/2" x 3/8". The PCV crossover looks to be the largest hose in the whole engine area and the only one of its size.

Since I needed both PCV hoses, I just went ahead and bought the Z1 kit for $32 since it gives me all 3 PCV hoses in all the different sizes. This way I dont have to buy multiple types of hose from another place for fitting on.


Thank you again to both of you.

[macgiver]

mac, righton enigma - I'll tell you a story about the original owner of my J30 ,rich businessman and didn't put a dime into the car , he had it till about 43kmi (2nd had it to 73k, I now got 260kmi).The crankcase actually blew out the dipstick , he coudn't keep it down , like "bad take-out" I knew the mechanics at INFINITI 's shop &they told me he only changed oil once or twice , and clogged some passages & hoses in addition to the TWO PCV valves - so yes a serious DISRUPTION , just the right(wrong) way ,can blow-out gaskets et all! Or the dipstick even ! PCV systems not all routed/designed the same at all - they just "attempt" to do what you say you recently read/learned . Good luck cleaning out or upgrading IS sometimes possible ,depending on your cars design.

[macgiver]

mac,enigma , rereading your original post(OP) , blowing the cover gaskets in COLDER weather , I have to caution you a blown head gasket can "route" combustion pressures either into coolant passages , OR into the CRANKCASE via oil drainback (head to block passages) ,more rarely BOTH situations . For I had powerful bubbles of exhaust forcing into my coolant overflow bottle whereas H-gasket failed on ONE cylinder - don't know if forced into pressurizing the crankcase. The KEY was weather , when colder the heads (aluminum alloy) SHRINK and thats when Head gaskets leak the most AND when they will fail "blown" before PROPER WARMUP! I warm-up fully ,my case being the NOTORIOUS 3.1L GM code M V6 in Cutlass'