Q: Car leaking oil, oil blows out of dip stick tube

asked by on

My car has these problems: broken speedometer, replaced motor mounts, windshield wiper that doesn't hit the window, light out on the dashboard, etc. But my question isn’t about those (just listing for your info). For a while, my car has been leaking oil (no burning). I was told that it’s a valve cover gasket. But I looked and the oil is coming out from underneath the oil filler cap on top of the engine. Almost like a blowback.

When I stop to fill up the gas tank and check the oil, if I have been driving for a while, there is pressure build up and blows a little oil out of the dip stick tube. The other day while it was running, when I opened the oil cap, it hissed with pressure like a radiator cap. There’s supposed to be oil pressure, but I’m wondering if this is normal. In your professional experience, is something blocked or clogged that causes a build up of pressure that spews oil out of the filler cap? Thank you.

If you had excessive blowby from worn rings and all, then you would have excessive smoking and oil consumption through the engine. It almost sounds like your PCV (positive crankcase ventilation) system is not feeding blowby gasses back to the intake so crankcase pressure is building up in the engine.

The Volvo 850 has a breather box located under the intake manifold. Make sure the vacuum lines to the box are not deteriorated or damaged, and if the box has never been replaced, then it might be a good idea to do so. Failure of the crankcase ventilation system can cause gaskets and seals to fail which can be very costly to repair if the system is not corrected immediately. You may want to enlist the help of a mechanic, such as one from YourMechanic, who will be able to give your car a comprehensive inspection and address all the issues that you’ve listed.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Car leaking oil, oil blows out of dip stick tube

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Q: Electrical problems

Hello, thank you for writing in. The fuse box will have a fuse/relay that will pertain to these systems. Before taking the car in for potentially costly diagnostics, check under the hood and replace this fuse. Your fuse box lid...

Q: I have p0203 dtc injector circuit malfunction

Hello. If this occurred right after the replacement then I would look for a pinched wire. It is common for there to be a wire that is pinched or loose or a bad connection. If everything is fine it may...

Q: I smashed into a curb,crackd my radiator,now the car won't stay in gear,what did I break?

The failure of the transmission to stay in gear could be due to physical damage to the shift linkage. That would be apparent on inspection and testing. If the radiator is damaged, you can request radiator replacement and that replacement...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.