Engine Degreasing


Engine Degreasing

You can damage the engine spraying cold water on a hot engine in some cases! It's not bunk. The old OM61x iron-head engines seem pretty impervious to damage and I've not heard of one acting up after a cold wash on a hot engine. HOWEVER, the OM60x engines with aluminum heads are a different story! Even after letting it cool so the dash gauge was down to 50-60C, I got frightening cracking and popping noises when using the high-pressure rinse at a coin-op car wash. Sure enough, I ended up with a few drops of oil in the coolant, which really really pissed me off (NEW head and gasket less than 10kmi earlier). The oil amount was tiny, so I torqued the head bolts in sequence another 1/8 turn each, and so far that has seemed to cure it. Had a similar problem with the old head & gasket as well. Don't screw around with aluminum head engines. My trick is to drive the car to the car wash, put the heater on MAX, then kill the engine but leave the key on. The electric auxiliary coolant pump will force coolant through the heater core and the fan on MAX will cool the engine significantly inside 15-20 minutes. Leave it like that while you're jacking up one corner of the car (for better access to the underside), and spraying Engine Brite on everything. Then rinse it.

Side note: The 3-prong temp switch on OM603 engines, that triggers the electric radiator fan in front of the condenser, DOES NOT like to get wet. If you spray it with water, IT WILL switch on and may not ever switch off. This has happened to two of my switches personally, plus at least 2-3 other people I know of - in all cases a new switch cured the problem. Simply placing the plastic cap from the Engine Brite can over the switch, to prevent *direct* spray on it, prevents the problem. But don't think everything electrical in the engine compartment is impervious to water spray - that just ain't true!

Dave Meimann







Ref: Frank Mallory's database and https://mercedes-benz-publicarchive.com