I have a 1990 240DL with about 227K miles. The brakes work fine in the city. On the highway, if I haven't tapped the brake pedal for 15-20 minutes, the next time I use it there is a slight delay before the brakes kick in. I'm thinking it is a question of having the brake lines bled, but I would appreciate any other suggestions.

 

does the pedal feel mushy when this happens ? thats the number one sign of brakes that need bleeding.

 

No, the pedals depress about the same as always. The only difference in feel is that when you depress the pedal and nothing happens for half a second, you get a sinking feeling in your gut.

 

if you feel the hard resistance in the pedal, the brake pads should be firmly against the rotors. there's no mechanism there that can introduce a delay in braking.

if you're not familiar with servicing brakes, you should bring it to a reliable mechanic ASAP to have the brakes inspected.

Question: does a 1990 240 have ABS? under the hood you'd see a fairly complex box clearly marked ABS with a bunch of gold brake lines going to, they are on one side or the other (on my 740 it was on the left/drivers side of the engine compartment, forward of the spring/shock tower). a defective ABS unit can do funny things to braking, but usually you feel it 'throbbing' when pressing down on the pedal.

a *non* ABS 240 has dual circuits to each front wheel, they both have to be bled, if one circuit isn't working correctly, you're supposed to get a red BRAKE warning light on your instrument panel, and you'd have half your normal braking power.

 

Most likely a master cylinder issue.