Existential cold start question - PeachParts Mercedes-Benz Forum

BenCohen-300TD · #1 01-13-2015, 11:07 AM

Hello all,

I love my 1979 300TD. I've put a lot of work into it and right now it runs great. It's got 160K miles. Unfortunately it has some pretty rusty spots and because it's a 79, I know one day soon I'll have to replace the climate servo. Also, it only starts cold down to about 20 degrees.

This is pretty good most of the time, but I live in the city and I never have the opportunity to plug in the block heater. So, when it's coldest and you need to drive the most, the car won't start. It has a new starter and 5W oil and strong glow plugs and okay compression, I doubt I'd be able to get the cold start temp much lower.

GF would like the AC to work, and it's a little too loud on the highway.

Existential Question: If I wanted to upgrade to a newer MB diesel, say a nice w124, would I have better luck with the cold starts and constant upkeep? Am I better off just fighting the good fight with my '79 and getting a good paint job for the rust, dynamat the ***** out of it and fix the AC?

Would this end up costing around the same anyway? Has anyone else had this dilemma?

It would be hard to give up my good old wagon...

leathermang · #2 01-13-2015, 11:32 AM

You have the York AC compressor ?
There are water heaters you can install in a radiator hose...for tractors for sure.....
Perhaps you can find a 12 volt one...
You have room to carry a spare battery... ...
the speed of cranking is very important to starting a diesel..
as is the condition and type of glow plug.. have you upgraded the glow plugs yet ? and reamed the glow plug holes so you know carbon is not interfering with the operation of the glow plugs...
these are little things which if all are optimized could erase your cold weather start worries......
I do worry about a straight 5 wt oil... what brand is it ?
Would be sad to wear out the engine while worrying about other stuff...

BenCohen-300TD · #3 01-13-2015, 11:47 AM

I'm not sure which compressor I have, I can check this evening when I'm closer to the car. You think this has some bearing on the decision?

Whoops didn't see your other comments:

That is an interesting idea about using a spare battery to heat the coolant. Thought about doing that to heat up the battery as well with a little heating pad. Has anyone tried this sort of thing?

The glowplugs are a year old and pencil type. I reamed the holes this summer. I'm replacing the valve stem seals this weekend to see if that helps at all. I'm not sure it's reasonable to expect starting much below 15F though. Do you?

The oil is Rotella synthetic 5W-40.

leathermang · #4 01-13-2015, 12:06 PM

Thank you for using a correct oil....
a little heating pad can be of help with the battery...........
The valve stem seals will not help the cold weather starting... but encourage you to replace them and the springs and rotators since you are considering keeping the car....and those are cheap things to do which pay off in the long run....
You have done so many of the correct things to address the situation I think only the block heating situation will pretty much get you to summer...
What ac refrigerant is in the car ? Have you done any tests as to why the ac is not working... did it ever work while you owned the car...
I am only asking about the ac since you mentioned your gf wanting it... which is good enough reason...

Zacharias · #5 01-13-2015, 12:46 PM

- When you replaced the starter, I assume you were sold the later version, for the turbodiesels? I hope so. It turns noticably faster than the old version for the NA cars.

- try adding kerosene to your fuel in the colder weather. I am in the northeast and am running a gallon of kero to a tankful. It makes a huge difference to how my car starts.

- use only Bosch or Beru glowplugs. Other makes are known to fail prematurely in these cars.

- ensure that your battery cables (connector clamps) and battery posts are shiny clean and the same for where the negative cable attaches to the fender.

- how do you preglow the car? Do you let the relay do its full 30-sec cycle, or are you trying to start the car when the dash light goes off? It is permissible to use two or even three cycles, to really heat the prechambers up.

JB3 · #6 01-13-2015, 12:54 PM

There is definitely a problem if it wont start below 20F.

You should be able to start off glow plugs well below zero with a few cycles

Zacharias · #7 01-13-2015, 02:31 PM

I just went back to your original post and I realized you did not mention valve adjustment.

If you haven't got the valves adjusted properly, you won't be able to start it in cold weather.

BenCohen-300TD · #8 01-13-2015, 02:44 PM

Thank you guys. This is very helpful. Quick answers:

- Starter is the fast one (I've actually been told they do not make the slower one anymore...). It is much faster than the one I had before.

- Glowplugs are Bosch.

- Valves adjusted in the fall. I think I did a good job. Runs great.

- Battery cables and starter cables got replaced with the new starter.

- When the pencil glowplugs were put in, I did not change the relay. Now the light doesn't turn off. Sometimes I just let it preglow for 2 minutes straight, sometimes I pretend that it turns off and run the GPs for 30 seconds, shut off, preglow again, etc. Leathermang mentioned in a PM that just because the light stays on doesn't mean the glow plugs are still on. Good Point! and worth checking on.

My last failed starts were at 12F and 15F and I have some anti gel stuff in the tank but not much. I'm going to throw some kerosene in there tonight and run it for a bit. It'll be 15F at 6am and I'll give it a go with the kerosene.

Anybody with experience in the w124? Can they do even better than 0F?

vstech · #9 01-13-2015, 02:45 PM

while getting this going and starting in cold weather is a good thing...

I LOVE my 201 and 124 diesels... they have more power, more comfort, airbags, and antilock brakes, modern a/c and did I mention the more power?

I mean, the 87 turbo 190D is amazing... the 87turbo 124's are equally so... the later 124 diesels are fuel sippers, and still have plenty of get up and go... and all of them have modern a/c... nice powerful blowers, and QUIET!!!

forget attempting to quiet the 79 with dynamat... there is an inch of it under your feet... the car is just LOUD!@!!!

leathermang · #10 01-13-2015, 02:50 PM

Vstech is correct in what he just said...
but no other car is as good looking and practical as a 123 MB wagon.

JamesDean · #11 01-13-2015, 03:14 PM

FWIW, I was able to start my 91 124 300D 2.5 at -14F with just a normal type of start up. I just waited until the glow plug light was off and then cranked. No longer than a normal cranking duration.

My dad's 300SD is a bit less easy to start up. It does take a few glow cycles to convince it.

dieselbenz1 · #12 01-13-2015, 05:52 PM

The 124 does start easier in the cold and is much more pleasant to drive than the 123. Looks of the 123 are better on my eyes though

JB3 · #13 01-13-2015, 06:07 PM

Quote:

Originally Posted by BenCohen-300TD

Thank you guys. This is very helpful. Quick answers:

- Starter is the fast one (I've actually been told they do not make the slower one anymore...). It is much faster than the one I had before.

- Glowplugs are Bosch.

- Valves adjusted in the fall. I think I did a good job. Runs great.

- Battery cables and starter cables got replaced with the new starter.

- When the pencil glowplugs were put in, I did not change the relay. Now the light doesn't turn off. Sometimes I just let it preglow for 2 minutes straight, sometimes I pretend that it turns off and run the GPs for 30 seconds, shut off, preglow again, etc. Leathermang mentioned in a PM that just because the light stays on doesn't mean the glow plugs are still on. Good Point! and worth checking on.

My last failed starts were at 12F and 15F and I have some anti gel stuff in the tank but not much. I'm going to throw some kerosene in there tonight and run it for a bit. It'll be 15F at 6am and I'll give it a go with the kerosene.

Anybody with experience in the w124? Can they do even better than 0F?

Somethings up, because a 123 can start below zero reliably if everything is in working order. Its not that 124s might start easier, but theres an issue going on with your car. Id start with getting the later relay.

My 240 would start first try down to -5 to -10 when i triple cycled the plugs and with 5w40 oil.

With a later relay, try letting the whole glow cycle happen. The light goes out like 15 seconds before the glow plugs are out. I would cycle the key and wait until i heard the relay turn off, not just the light

BenCohen-300TD · #14 01-13-2015, 06:10 PM

Thanks again guys this is great. Thanks Vstech, I'm glad to hear people love thier 124s. I feel like I don't see as much posts around here about the 124s as the 123s. I was hoping that's because they are more reliable, not because they're all gone

I'm going try the kerosene thing tonight and test a really cold start tomorrow. -14 is going to be hard to beat, but you almost never see those temps here in NY.

Leatherman is right, the 123 wagon is a thing of beauty. I didn't realize the 124s had Airbags and ABS. I'm going to have to drive one this weekend and see for myself (not the airbags part).

I'll put up a pic of my wagon later on and see if anyone is interested. Would love for it to stay "in the family" if I do decide to let it go.

Thanks!

JB3 · #15 01-13-2015, 06:14 PM

The 124s do ride really nice. Locally there are several cheap wagons. Ive been considering jumping into a gas one for the wife

One thing you will like coming from a 123 is you can see the 123 in the 124. Everything is just a bit more modern and a bit different shape, but its like an old friend who had some plastic surgery and looks younger