Skip the auto shop - Our mechanics make house calls

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 1000 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: I thought I had a bad starter turns out that it was a bad battery I installed a new battery and I could not turn the lights off,

Hello. If the lights are staying on then you more than likely have a bad combination switch. The switch fails internally and causes this. It can also be a relay that is staying on, but that is not as common....

Q: Idle air control stuck closed and the car won't hold at idle

Generally, a little air will pass through. But the thing is, the idle air control valve controls your idle speed. If that is shut, you are not going to get enough air bypass and the car will idle low enough...

Q: '98 VW Bug endless oil leak

Hi there. The valve cover gaskets are probably worn and need replaced. If all of the gaskets are replaced and there is still oil coming out of the engine, then replace the positive crank case vent valve (PCV). If the...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
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...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...