Hi Guys, It seems my 300 is starting to fall apart.
Which is surprising as I try to really stay on top of maintance. Right now it dosent want to cold start and idles rough while in gear.
History,
Everything was running great until it overheated one day, I began changing parts (the radiator was changed about months before), anyways I changed out the thermostat, hoses, waterpump, heater valve/pump. Its still using water possibly from a crack in the plasitc water tank (thats the least of the problems).
Soon after it began idling rough (for no particular reason). Oil and water are all clean and clear.
I figured 60,000 miles since rotor and cap hopeing for an easy fix. After new cap, rotor, plugs no change.
Injectors were changed new 60,000 miles (still hav originals in boxes that ran like new).
Question where do i start?
I changed out the start relay (little black box by battery) and OVP relay about 2 months ago as preventative maintance. Should I put the old ones back in??
Could an accumulator cause rough Idle?
I'm open to reccomendations,
Thanks,
Alex
89 300E 197,000

Sorry Alex, but this is the wrong forum. You want to post this in Tech Help. We don't do caps and rotors over here.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

Alex, welcome aboard!

Rick, you're taling about injector return line caps and disc brake rotors, right? I can't think of any other rotors or caps on an automotive application... I also don't know how a set of glow plugs would affect a warm rough idle...

Seriously, Alex, I hate to say it, but have you thought about the possibility of a bad head gasket? I don't know beans about M-B gas engines, but if you severely overheated the engine (ESPECIALLY if it's an aluminum head/iron block assembly), there's a very real possibility of tha thaving happened. I'm sure that others wil have a better idea, but you might check the tailpipe for white sweet smelling smoke and also try a compression leak-down test. If you're getting coolant into a cylinder, that would explain the coolant loss as well as the rough idle.

Hope that helps a little bit...and, as Rick said, you may want to re-post this in the Tech Help forum. Good luck!

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2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
Spark-free since 1999

Alex:

Coolant loss it a bad sign, especially if accompanied by cold pressure in the coolant tank. Check tomorrow morning -- if there is pressure in the cooling system (hard hoses relieved by opening the coolant tank), chances are you cracked the head.

However, before you panic, check the idle control valve hoses (it's under the air filter housing) for cracks or leaks -- they get hard and loose on the fittings, so they leak air and you don't get enough through the fuel distributor to get it to deliver any fuel to the injectors when cranking. The cold start valve plugs into one of them, too, so a leak there will cause trouble.

You probably roasted the temp sensors in the head, too -- replace them (or at least check them), that may solve the problem.

Rought idle can also be bad engine mounts, too, unrelated to running problems. If the vibration is significantly less in reverse than in forward gears as idle, replace the engine mounts, you will be amazed.

I'd also check all the wiring on the engine, too -- heat as high as you got tends to make the insulation brittle, so you may have a short or ground somewhere.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

First Let me apologize for posting this message on the wrong board (no wonder i couldnt find a reply). I guess I was just drifting thru your diesel page dreaming of one not having to worry about caps and rotors when I posted in the wrong place (or is it fate?). To u smart A's yah yah yah, I know what yer sayin! Ya otta be ashamed of yourselves kicking the guy just cuz he's down with that gas engine!
Finally Yip I guess I gotta start thinking about the water disappearing into the cylinders.....sad but true. But wouldn't I be seeing it in the oil??
Now a leakdown test does that push pressure thru the radiator tank and create bubbles??
Thanks,
Alex

If you get white smoke that smells of glycol, you have a cracked head.

A leak down may or may not show pressure in the rad -- but a leaking head gasket will.

Get a compression check and leakdown done -- if you have a badly warped head, the head gasket will leak out somewhere, and this will usually show up on a leakdown in the rad -- but then, it will also "boil" on a cold engine. My sister's Volvo blew coolant up in the air after she fried hers on the interstate (actually, my nephew was driving at the time).

That one was bad enough I could rotate the engine by hand, so I suspected a blow gasket to start with (they ran it til it stalled.....).

If the gasket is leaking, expect a warped head, which will probably mean a new one if you overheated it greatly.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!