Metal cap on engine top burst today after replacing my turbo boost pressure sensor.

2000 Volvo S80 T6 2.8L Twincharged

A while back my turbo boost pressure sensor started acting up and really messed with my RPMs. To the point that I could still drive it but I had to be careful when accelerating otherwise I would lose all acceleration and would have to restart the engine.

I drove it like this for about a month (I know) because I am a college student with **** for money. I drove it very lightly and was careful. Probably 2 or 3, 10 mile trips a week.
I finally got enough money to purchase the part from RockAuto (btw kudos to them for shipping it so quickly).

Today I put on the new turbo boost pressure sensor and went for a drive. It was absolutely beautiful and smooth sailing. I drove up to the freeway and back down the highway to my house. About 1 miles from my house I smelled oil and figured it was the big mechanics truck in front of me. I got to my house and ran inside to grab my wallet.

On my way out I noticed there was smoke coming from my engine so I ran over to my seat and checked the temperature gauge but it was completely normal.

I turned off the engine and lifted the hood to find that this cap (pictured below) was blown out of its hole and there was oil EVERYWHERE. I checked my oil and added about 2 quarts.

I've been looking everywhere for what this cap is called but I cant find anywhere that can clearly define it. I've seen it called a valve cover, a cam cover, and freeze cap. I just want to know what I need to order in order to fix this thing.

My assumption is that the newly fixed turbo air pressure created a lot of buildup and blew it off.

Also, if I buy a new piece wont the pressure just blow the new one off as well?

 

google "volvo 1361451" to see if that part number matches up. As far as being related to the turbo fix, I'd say its more likely related to the PCV system. Your turbo boost should be contained to the intake (ie turbo, through the tubing to the intercooler and up into the MAFand throttle body). The PCV system does plug into the path to produce a vacuum and pull the crankcase gasses into the intake. A failed oil separator (aka flame trap) or clogged PCV could create positive crankcase pressure which can cause oil leaks/push out seals etc. The quick test is to put a latex "surgeons" glove over the oil filler port and see if it inflates and stays inflated (bad). Normally it should suck in or puff in and out...

 

YES that is the piece.

So I tried the glove thing and nothing happened. It was not blown out and it was not sucked in. No change at all even slight.

Also I'm not so sure about it being a PCV issue yet. I just find it unlikely that coincidentally the thing blew its cam cap right after I changed the turbo boost pressure sensor. I hadn't had any other problems with anything mechanical until now.

I think maybe the newly restored boost might have punched too much pressure on the weak point that for a month had been getting weak pressure.

Anyways, what should I do? I am extremely broke atm and can barely afford to get to my classes via bus (45 min drive). And I just found out the piece alone (if it is the PCV) is $500 and tricky to get to.

like I said the glove doesn't suck in or inflate so?
Any other ideas?

Thank you

 

if the glove doesn't inflate or suck in, that indicates your PCV system has neutral pressure which is acceptable. The boost sensor controls the waste gate which in turn limits the maximum boost sent into the intake air path (hose comes up from the turbo into the intercooler then into the MAF/Throttle body. the only connection I know of between the valve cover is from the intake air path to the oil separator and then via the PCV tubing back into block and the air pressure could follow the oil passages up to the head. The oil separator's supposed to be a one way street, ie the intake vacuum is supposed to suck the air from the crank case not push air pressure into the crank case so that's why I'm thinking to look at the PCV system.

 

But if the PCV is acceptable why would it have blown the top?

 

normally PCVs fail when they get clogged with oil and sludge so the blow-by gasses have no place to go. I'm curious if its possible that the oil separator can fail by opening up and allowing the boosted air to push back into the crank case. I suppose if you put your hand over the oil fill port and revved the engine (enough to produce boost) and felt air push out, particularly when you let off the throttle (to close the plates) then that would say the boost is connected to pushing out the cap. Further I'm wondering what could cause such a failure - ie just a bad oil separator or if the turbo's blow off valve is not opening and giving all that pressure some place to go when the engine is deccelerating...

 

So I just had a friend rev the engine a few times and even hold the accelerator down while I hovered my hand over the oil fill port. While he accelerated I felt air flowing out of the oil fill port that stopped when he took his foot off of the accelerator. I didnt notice it get any faster when he stopped it just sort of stopped with him. I also put the glove back over the port and it inflated about half way and then deflated when he let off.

In other words when accelerating there was a steady flow of air (like a small fan) coming out of the oil fill port that stops when the engine idles.