block heater usage, how is too long?

[rickjordan]

Here in NJ it has started to get cold in the mornings, so I have started using the block heater. I was wondering if there was a maximum amount of time you should have theses plugged in. Is there any danger in plugging it in at 11 pm, and let her warm up all night. Someone told me to get a timer and set it for 2 hours or so prior to starting the car. I have already once plugged it in overnight and in the morning the valve cover was nice and warm, and she crank right over and idled smooth. Just looking for everyones opinions on this. This is my first car with a block heater.

------------------
1980 MB 300SD
1999 VW Passat Wagon

I HAVE LEFT MINE ON FOR DAYS. I HAVE 2 300'S, I FIND THAT WHEN IT IS BELOW 10 DEG. F, I HAD BETTER USE THE BLOCK HEATERS. MY OLDER ONE WILL NOT START WELL IF IT IS BELOW FREEZING (POOR COMPRESSION OVER 350k MILES). I FIND THAT TURNING THE GLOW PLUGS ON MORE THAN ONCE WHEN IT IS REAL COLD HELPS. IF IT DOES NOT START RIGHT OFF, TRY ONCE MORE & THEN FORGET IT, YOU WILL JUST RUN THE BATTERY DOWN. YOU HAVE BATTERY OR OTHER PROBLEMS. I HAVE BEEN TOLD TO START THEM UNPLUGGED TO AVOID THERMAL SHOCK TO THE HEATERS, BUT I HAVE NEVER BROKE ONE YET.

[Benzmac]

The drawback that I am aware of is the power consumption. I think that they are 400-500watts. This is like 8.5 60watt bulbs burning over night.

------------------
Benzmac:
Donnie Drummonds
300E
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM
OWNER OF MB AUTOWERKS .COM

[Chris Haney]

I have heard some use a lamp timer to start warming about two hours before anticipated starting.

------------------
1991 350 SDL
125,000 miles

[rickjordan]

Thank you for the replies. I plugged it in last night at about 11:30 pm. At 7:30 this morning she cranked right over, idled smoothly and the eng. temp. gauge read 40c. which works out to be about 110 deg. F. It got down to about 27 degs. last night. Had I not plugged her in, she would of idled real rough. It's like a gas eng. not firing in one of the cylinders. This only happens when she's cold.

------------------
1980 MB 300SD
1999 VW Passat Wagon

You should feel comfortable and not worry about leaving your benz plugged in all night. I did so with my 300D last night for the first time, and it helped. Running the glow plug cycle 2 or 3 times seems to help a lot as well. I used to do exactly the same with my first car, a 1980 Bonneville 5.7 Diesel. Except when one day i pulled out the plug to plug it in, the whole cord came out, Oil leaked so badly around that engine it melted the cord! Remember to keep the cord away from the fan as well! Just my $0.02.


------------------
83 300D-T

Out here in the mountains of eastern Washington we have been below freezing for three weeks now, sometimes as low as -3F. This is my third year with my 300D and it gets plugged in when I get home from work and stays on until I leave the next day, or all weekend if I don't drive it. No problem with the block heater to date. Just bought a 300SDL today and hope it provides the same results.

I've used my block heater overnight several times and I think it's ok to do it once in a while. Unfortunately, block heaters can get so hot that they'll burn the additives in the coolant. Eventually enough crap will crust and harden on the block heater that it will seriously diminish the heater transfer ability of the heater. Therefore it's probably not a good idea to make a habit of keeping it plugged overnight everynight, especially when 1.5 hours is usually enough.