Skip the auto shop - Our mechanics make house calls

Q: Truck idled, ran rough, fluid streaming from motor

asked by on

A very bad knocking noise has developed in my dad’s truck recently. It has that sound as if something is loose. A couple of days ago when I was driving his truck and I got to his house, the truck idled, was running rough, and then the engine almost shut down. There was a stream of fluid pouring from the motor and so I opened the hood and saw that the master brake cylinder lid was loose and the brake fluid was spilling everywhere. Now, the truck has a muted knocking noise when I start it. My dad thinks he changed the oil and put synthetic oil instead of regular 10w-30. So I'm thinking that he did not change the oil and kept the same oil that was in it and just added the synthetic oil. I don't know if this happened or not. He’s a bit forgetful these days. I don't know if that is what would make the knocking noise, or not. Perhaps it is the brake fluid that has gotten inside the cylinder. The oil pressure lights read a bit high and my dad also told me that the truck has stalled coming up their road. Now he has no transportation and I want to fix this for him; he needs my help. We are hoping that it is a simple fix so he won't have to scrap this truck. In your experience, what will fix my dad’s truck?

Hello there, thank you for asking about your car. It’s highly unlikely that brake fluid entered the combustion chamber. The noise also would not be caused by using synthetic oil instead of conventional oil. As for the oil pressure, I’m not sure what your dad considers too high. With the engine fully warmed up, oil pressure should be about 24 psi at 3,000 RPM. To know for certain what’s going on, a professional will need to listen to your vehicle firsthand. A certified technician from YourMechanic can come to your home or office to inspect why your truck is idling roughly and make any necessary repairs.

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

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: Car runs but knocks

Hello. It sounds like there may be something inside the engine that is worn out or broken. This will cause a knocking noise and could also cause the truck to shut off. A compression test checks the compression of each...

Q: What can cause the RPMs to go super high while driving at one constant speed?

Hi There, It sounds like you are describing the symptoms of a failing throttle position sensor. The throttle position sensor monitors the throttle position of the throttle plate inside the throttle body in relation to your foot position on the...

Q: Car died and clear, greenish substance on top of engine

The only fluid I know that has a green tint is coolant. You may have leaked out all the coolant or the coolant shorted out the ignition system. Check the coolant level after the engine has cooled down. If it...

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...
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.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.