Steam coming form under the hood

MOBERG311

MEMBER
1998 OLDSMOBILE BRAVADA
196,500 MILES

Today I noticed steam coming from underneath my hood. I pulled into walmart parking lot thinking it was just running hot. I went shopping came back out checked my oil and coolant and levels were good. I looked underneath the truck no leaks on the ground. So I drove the 15 mins home. When I got home same thing steam coming out, the only thing different this time while driving home the brake light came on. I called my step father in law and he thought maybe since the roads were wet that the water was splashing up on the hot engine block. He suggested since I do not hear knocking noises, no smoke or fluid from the tail pipe or any fluid on the engine block to run it for 10 to 20 mins and see if I see the steam. I let it idle for 20 mins in my driveway and no steam. I drove to work and when I got to work the steam was back. The temp gauge stays under 210 so I do not think it is over heating. I also do not smell anything. I am so confused please help

1 Reply

CARADIODOC

MECHANIC
33,742 POSTS

I wish I could be there to see it, but since the coolant level is okay, it's obvious we have to look for something that's NOT obvious. The place to start is with the brake warning light. Is it red or yellow? If it's red, it could be a coincidence that it turned on right now, but my guess is there's a pinhole leak in a steel line and the brake fluid is spraying onto hot engine parts. You would feel the brake pedal slowly sink down as you hold steady pressure on it. Don't allow it to go more than halfway to the floor. Doing so will usually damage the master cylinder on older vehicles due to crud and corrosion that build up in the bores where the pistons and seals don't normally travel. Pushing the pedal to the floor runs those seals over that crud and that can rip them.

Start by checking the fluid level in the master cylinder reservoir. Usually you can see it through the plastic housing, otherwise just pop the cover off. You can add a little if necessary to get to a repair shop, but be absolutely certain to not get a single hint of a petroleum product in there like engine oil or power steering fluid. That contamination will result in a very expensive repair bill.

Transmission fluid could be spraying onto hot engine parts too. If you have an automatic transmission, there's two cooler lines that run to the radiator. Usually it's not the steel lines that leak. It's typically caused by a leaking snap-together quick connect fitting or a rubber connecting hose.

The transmission fluid may not leak when the transmission is in park. You would have to have a helper look under the hood while you hold the brakes on and put the transmission in drive with the engine running. The brake fluid likely won't leak through a pinhole leak unless you're pressing the brake pedal. Either of those would explain why there's no smoke / steam while the car isn't moving.