86 420sel Brake/engine Questions - PeachParts Mercedes-Benz Forum

82LANDYACHT · #1 11-28-2007, 06:08 AM

I have an 86 420sel and I have some brake problems. I replaced all 4 calipers and bled the system a couple of times but the brakes still fell mushy. When you get into the car the brakes feel fine but as soon as you start the motor the pedal goes almost to the floor. Also, it has a click coming from what I think is the left cylinder head. I pulled the valve cover and everything looked ok. Lastly, I have an oil leak coming from somewhere in the back of the motor. It only leaks when I run the car and comes out of the two holes on the bottom of the engine through which I think I can see the fly wheel. Any advice would be appreciated. Thanks.

wbain5280 · #2 11-28-2007, 08:06 AM

When you replaced the calipers, did you also replace the brake hoses? Why did you replace the calipers?

Did you check the master cylinder for leaks and brake booster for brake fluid?

The tickeing sound can be an exhaust leak. Check the manifold gaskets and EGR valve gasket and pipes. The EGR pipe that goes into the intake manifold can also get blocked with carbon buildup, assuming yours has an EGR vavle.

Your oil leak can be caused by a leaky rear seal. Also, the valley under the intake manifold has a drain hole at the rear left that drains onto the bellhousing.

A pressure buildup can also cause an oil leak past the rear seal. You have to check the crankcase venting system. Take off the air cleaner housing and check the small pipe under the passenger side for blockage, mine had it. Clean it our if it's blocked. Next, pull off the driver side hose from the valve cover to the cold start valve housing. There is a small hole that can become blocked. Push in a small pointed object, a small drill or the point of a test light, to make sure it's clear.

david s poole · #3 11-28-2007, 09:37 AM

when testing brakes remember that for pedal to go down fluid has to be displaced.if you put a pair of needle nose visegrips on each brake hose and repeat your test and the pedal still goes down you can blame the master cylinder.if it does not go down release the grips one at a time and which ever one causes the brake pedal to go down is the wheel where your problem is.

ctaylor738 · #4 11-28-2007, 11:03 AM

If the pedal was firm before, you probably still have some air in the system from your repair.

IMO, the only way to do this is with a power bleeder at 15-20 lbs psi. The sequence is RR, LR, RF, LF. You need a clear tube and a good light to see if there are any air bubbles coming out of the caliper fittings. Until you get rid of even the tiniest bubbles, you will have mushy brakes.

This can take a while, and a lot of brake fluid.