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Old 07-23-2021, 04:41 PM   #1
greatestntm
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Default Too much cranckcase pressure even with a catchcan?

Hi everyone,
In January, I did some work on my car and some of the modifications I did were a set of redblockpowered chips and a Yoshifab catch can.
I used the car mostly for city driving for a while like this with no real problem.
But a couple of days ago I was on a going on vaccation with my car which is a 1996 940 with a B230FK. The drive was about 8 hours of highway and in the middle of my journey I noticed that the engine was puking oil from the oil cap.
At this point my PCV setup was a yoshifab catchcan only routed with the stock block vent and return and the top port that goes to the air intake right before the turbo.
About 2 hours before I was supposed to arrive, the oil filler cap popped eventough it was tight and all of my engine oil leaked everywhere in my engine bay.
I found some oil and filled it back up and also installed my yoshifab vented oil cap that was actually in my trunk.
Even with the new cap, oil still found it's way trough the seal.

After I arrived to my destination, I did a proper oil change and cleaned everything up but the oil cap still leaks eventhough I tried with 2 different gaskets.

Do you guys have any idea of what might be the source of my problem?

Also, is it normal that even turned all the way closed the Yoshifab oil cap feels way loser than the stock cap?
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Old 07-24-2021, 12:53 PM   #2
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The oil drain hose under the oil trap box can clog with crap and cause high crankcase pressure. You can clean it out with a very stiff bristle brush like a rifle brush. Also be sure the port for the small hose on the intake is clear. Also check that the hose that goes to the intake pipe by the throttle body isn't filled with crap.

The tabs on the oil filler cap may need to be very slightly bent so they pull the cap tighter to the valve cover. At least that works with the stock cap. Not sure if that would work on the yoshifab cap. Try getting an oem gasket for the cap as it may be thicker than the aftermarket ones.
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Old 07-24-2021, 03:11 PM   #3
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Originally Posted by dl242gt View Post
The oil drain hose under the oil trap box can clog with crap and cause high crankcase pressure. You can clean it out with a very stiff bristle brush like a rifle brush. Also be sure the port for the small hose on the intake is clear. Also check that the hose that goes to the intake pipe by the throttle body isn't filled with crap.

The tabs on the oil filler cap may need to be very slightly bent so they pull the cap tighter to the valve cover. At least that works with the stock cap. Not sure if that would work on the yoshifab cap. Try getting an oem gasket for the cap as it may be thicker than the aftermarket ones.
Thank you for your answer!

I will clean the return and the block vent tomorrow.
The 10 AN hose that goes from the catch can to the intake between the MAF and the turbo is brand new.
As for the small vacuum hose that was going from the flame trap to the intake manifold, I thought it wasn't used anymore since it is not mentioned anywhere on yoshifab's website or on Dave Barton's installation of the catchcan.

I will also try to bend the tabs on the oil cap. I already have an OEM gasket which is indeed thicker than the one that was provided with the Yoshifab cap.
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Old 07-24-2021, 04:14 PM   #4
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The small hose on the intake manifold is used to provide vacuum at idle to improve the pcv flow. It's not totally necessary as the 240 turbos didn't use it. But every bit helps and it's stock on the B230 turbo engines.
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Old 07-25-2021, 11:18 AM   #5
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Quote:
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The small hose on the intake manifold is used to provide vacuum at idle to improve the pcv flow. It's not totally necessary as the 240 turbos didn't use it. But every bit helps and it's stock on the B230 turbo engines.
That hose was deleted on 240 Turbos by Volvo. I assume the same for the 700-900 Turbos. If you're going to add this hose, consider adding a one-way valve so boost cannot flow into your crankcase when you have boost.

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Old 07-25-2021, 11:24 AM   #6
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And if by chance you're using the brass filter thing, try removing it.

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Old 07-25-2021, 11:41 AM   #7
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Thank you for the information Dave.

I had a vacuum line like this going to the intake manifold with the stock PCV system but I deleted it when I installed the catch can.

This morning I cleaned the return plastic tube that goes in the block and it seemed like it was in fact clogged.
After that I bent the metal tabs on the Yoshifab filler cap and now when it goes on it's much snugger.
I then went for a test ride of about an hour and when I opened my hood, it was way better than before. One or two tiny little drops of oil had leaked out of the filler cap but that was all.
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Old 07-25-2021, 12:15 PM   #8
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Crankcase needs enough vacuum to keep the oil cap in place.
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Old 07-25-2021, 01:17 PM   #9
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The 940 turbos have the vacuum line.

I'm having the same problem, but I have a Holset HE351CW and I'm running 25PSI. I'm in the process of building a serious PCV system with a McNally catch can, Yoshifab block adapter and a Ford Evap pump which will be boost referenced to turn on and off.
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Old 07-25-2021, 02:49 PM   #10
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I added a another catch can so I have the factory oil trap going to one catch can and a B20 vented cap going to another one, I also put some black gasket maker on both sides of the valve cover gasket. This has cut down considerably on my oil leaks.
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Old 07-25-2021, 04:39 PM   #11
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Quote:
Originally Posted by Jack leg View Post
The 940 turbos have the vacuum line.
Do they use a one-way valve?

Quote:
Originally Posted by Jack leg View Post
I'm in the process of building a serious PCV system with a McNally catch can, Yoshifab block adapter and a Ford Evap pump which will be boost referenced to turn on and off.
Can you point us to this Ford Evap Pump? Googling finds quite a variety.
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Old 07-25-2021, 10:58 PM   #12
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The boost pressure that does try to go down the small hose is sucked back to the intake of the turbo by the large amount of vacuum at the turbo intake when under boost level of flow. So there was not a one way valve used in the pcv small hose.

I like the method Stealthfti used to improve crank case ventilation. He added a fitting to the pcv breather box and then ran both large hoses to a catch can. From there a vacuum hose to the turbo intake hose. https://pbase.com/stealthfti/pcv
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Old 07-25-2021, 11:09 PM   #13
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Quote:
Originally Posted by dbarton View Post
Do they use a one-way valve?
The only valve in a 7/9 turbo vacuum system goes to the climate control hose.

This might be an obvious statement, but if you had a lot of engine wear it would manifest as a lot of smoke on acceleration. Like if you were pressurizing the interior of the engine, ask me how I know haha. Must be a gasket problem. Hope the oil cap thing fixed it.
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Old 07-25-2021, 11:14 PM   #14
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Quote:
Originally Posted by dbarton View Post
Do they use a one-way valve?


Can you point us to this Ford Evap Pump? Googling finds quite a variety.
They do not use a one-way valve or check valve.

Search secondary air pump in Amazon or Ebay. They're everywhere.

Here it is installed and with my hand for a reference.
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Old 07-26-2021, 03:10 AM   #15
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Quote:
Originally Posted by 2turbotoys View Post
This might be an obvious statement, but if you had a lot of engine wear it would manifest as a lot of smoke on acceleration. Like if you were pressurizing the interior of the engine, ask me how I know haha. Must be a gasket problem. Hope the oil cap thing fixed it.

Yeah with all this pressure, I was expecting to see smoke at the tailpipe but to my surprise, it didn't smoke at all.
The oil cap seems to be OK now I'll have to drive a bit more to confirm that.
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Old 07-26-2021, 07:35 AM   #16
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I haven't seen it mentioned, but how good is your ring seal? Have a recent compression test?
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Old 07-26-2021, 07:38 AM   #17
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I haven't seen it mentioned, but how good is your ring seal? Have a recent compression test?

No, no compression test.
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Old 07-26-2021, 01:32 PM   #18
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Nice engine Jack! looks like 25psi is a lot of fun.
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Old 07-26-2021, 02:49 PM   #19
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Are you certain it is not detonating?
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Old 07-26-2021, 03:42 PM   #20
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Are you certain it is not detonating?
I'm fairly sure it doesn't.
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Old 07-26-2021, 07:58 PM   #21
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Nice engine Jack! looks like 25psi is a lot of fun.
I appreciate it! Lot of work and I'm still ironing out kinks, like excessive crankcase pressure, fuel delivery and idle characteristics. My first rebuild and while I did some things right, I didn't do so well on others and this took me 3yrs to get to this point because I have a ton of kids. This thread made me want to chime in because I've been dealing with the same issue and have gone down the rabbit hole of PCV systems.

Here is my new catch can for the PCV and the pressure switch to enable the evap pump.
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Old 07-27-2021, 06:59 AM   #22
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I'm interested in how you plan to do the plumbing on that pump. Will there still be a hose going to the air intake before the turbo?
And will the catch can be draining oil back to the crankcase?
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Old 07-28-2021, 08:05 PM   #23
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I have problems with crankcase pressure on my 88 765 T with 343K miles. I have tried many things including mounting a Chrysler V8 breather cap on the valve cover. Never got it to run all that well. I now have a catch can installed with the block mounted oil trap outlet running into the catch can. I have two outlets from the catch can. One outlet run with a check valve with the arrow toward the intake manifold vacuum nipple and one outlet with a check valve with arrow toward the turbo inlet. I now have enough vacuum in the valve cover to hold the loosened oil cap in place.

Funny thing is my mpg have increased.
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Old 07-30-2021, 05:37 PM   #24
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Quote:
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I'm interested in how you plan to do the plumbing on that pump. Will there still be a hose going to the air intake before the turbo?
And will the catch can be draining oil back to the crankcase?
Dave
I'm in the middle of doing the plumbing and should be done with the install maybe tomorrow. I'll post pics then.

However, plumbing will be block to McNally catch can, then 1 hose will leave the McNally and go straight to intake pipe for
the turbo while the other hose leaving the McNally will go to the pump then leave the pump and go to the intake pipe for the turbo. Meanwhile, the secondary catch can will have a hose leaving one of its nipples and going to the oil cap and a breather filter on the other nipple.
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Old 07-30-2021, 07:47 PM   #25
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Progress
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