Dumb Question 603 diesel - PeachParts Mercedes-Benz Forum

brandlj · #1 01-31-2008, 05:57 PM

Hello everyone,
Here is a dumb question, but I am going to ask anyway. The battery in my 86 300sdl is getting up there in age. It is now 8 years old. I am noticing that in the morning, the glow plugs are not getting very warm. I am surmising this because my car misfires and blows blue smoke when cold. It smooths right out as soon as I start driving. If I plug in my block heater, it starts perfectly fine in the morning.
I checked voltage on the battery and it is 12.0 volts. If I double glow plug it, then it won't turn the starter very well. I know it is time for a new battery, but the question is, will the glow plugs not get as hot as needed when the battery is old or low? The timer in the glow plug relay turns the light off just as it did when the battery was new.
I guess what I am asking is, could the low battery make it harder to get a good glow, or should I also look at replacing the glow plugs.
This car is no longer my daily driver. I came across a fantastic deal on a 2007 530i with only 2000 miles on it.
I know this is blasphemy, but man oh man, do I enjoy driving a new 530i every day.
I am not selling the Benz, I plan on driving it at least two days per week until my 14 year old gets his license and then I will let him drive the tank to school.
I can't think of a safer car for a 16 year old to drive.

John
86 300sdl 105,000 miles
85 380 se 160,000 miles
67 VW Beetle restored with A/C
07 BMW 530i
00 Toyota Camry ( daughter's car )
03 Honda Odyssey ( family vehicle )

( you should see my car insurance bill every month )

TX76513 · #2 01-31-2008, 06:06 PM

John - great cars for new drivers.

Stop in your local box auto parts franchise and have them check your battery. After load testing they can pretty much tell you where the battery is. 8 years on a battery probably due. On the outside you might have a bad or week glow plug. Your weathers probably close to ours so we won't talk about our cold 30F mornings and freak out our northern forum members. My SDL will choke and sputter a little, but smooths right out.

brandlj · #3 01-31-2008, 06:13 PM

I have noticed my dome light is also dimmer in the mornings. I'll bet it is the Battery. Yes we are in the same area for winter weather. When it gets down to 24 degrees, we are FREEZING!!!
I drive through Brandon on the way to Tuscaloosa quite a bit. My daughter is a freshman at the Univerity of Alabama. The McDonalds across from Gray-Daniels Ford is our first stopping point for bathroom breaks. It is the halfway point from West Monroe to Tuscaloosa.

The 300sdl loves that 300 mile trip. I blow out a lot of city driving junk on that trip. It is a true Interstate cruiser.

John

pawoSD · #4 01-31-2008, 06:15 PM

I am 100% sure your battery is toast....I'd change it out before it leaves you stranded.

TX76513 · #5 01-31-2008, 06:15 PM

Mickey Dees, that where I get off of I 20 to head to the house. I get over to Monroe every other month, but stop at "The World" in Delta (on the way back)

One thing about the diesel if you can get it started you can drive it - alternator went out in NOLA once and drove back after I jumped it.

Thanks for the rain today

bustedbenz · #6 01-31-2008, 07:14 PM

12.0 is too low.

A charged battery that is in good condition reads 12.6 volts with no load.

brandlj · #7 01-31-2008, 09:01 PM

I thought 12.0 volts was too low. The Battery that I have is a Bosch and the repair facility that this was purchased from 8 years ago is out of business. Any input on Autozone or O'Reilly batteries. There is no MB dealer within 100 miles. Oh, what about an Interstate Battery? or WALMART brand?

Thanks for the replies and the info.

John

rcushman · #8 01-31-2008, 09:33 PM

Interstate actually OEMs the replacement battery for Mercedes... the model is the MTP93... I have one that's 7 years old that's still starting my 300SDL in below zero Maine winter weather. Price is only slightly more than a walmart battery.

brandlj · #9 01-31-2008, 09:52 PM

EXCELLENT!!!

Thanks for the info.

John

bustedbenz · #10 01-31-2008, 10:40 PM

Just personally, I refuse to buy anything at wal-mart that I can possibly get somewhere else.

brandlj · #11 02-04-2008, 03:55 PM

UPDATE:

I removed old Bosch battery and removed the caps that say NO MAINTENANCE needed, and lo and behold, the cells were half empty. I filled the battery with distilled water and performed a 48 hour trickle charge and now the battery is showing 12.4 volts. I put the battery back in and it is like it is a new car again. Glow plugs are heating well, and the car is starting like a champ.

I hope it lasts, if not, then a new battery is in order.

John