First road trip observations... - PeachParts Mercedes-Benz Forum

pizzachef · #1 01-29-2007, 11:38 PM

We took the wagon out on the road for the first time since buying it a few weeks ago. It was just a 5 hour trip each way between Harrisburg, PA and Albany, NY, but much longer than the around-town driving that we've done so far.

So the first thing that I noticed is that the speedo is about 12% faster than what the gps says. The car's got 195/70R14's, is that the right size tire?

Next, the temp sits right at about 85*C up until 60mph (gps speed), then at 65-75 it increases up to ~95*C. And hovers somewhere between those temperatures as we went up and down hills, sped up to pass, slowed down, etc. The outside temp was below freezing, around 20*F. So I was wondering what it would be like when the summer months came. I plan on doing a citric acid flush when the weather warms up, but are these operating temps about normal?

Next, the mileage I got, averaging 65-70 mph, was around 27mpg, but adjusted for the 12% offset in the speedo, that brings it down below 24mpg. Are others getting better? I had the tires inflated to their recommended max of 44psi...it was a bumpy ride in some places.

Lastly, and this is more of is sob story, heading back through PA, we hit some heavy snow around Scranton and had to slow down quite a bit. The car handled surprisingly well with the all season tires...I wasn't expecting snow on the trip, the weather said flurries

. Anyway, its arount 10pm and we're moving along at a cautious pace of 40mph on the snow-covered interstate, and out of nowhere someone in an Acura sedan rams us in the rear. There were no other cars around me. We pull over, the old guy barely speaks english, and I call the cops, try to get the guy's insurance info, he doesn't cooperate and leaves. Now I'm on the side of the road in the snow with a liscence plate number, a smashed tail light, dented hatch door, and bent up bumper. The police show up I tell them what happened, they get my info and go looking for the guy. They called today to say they know where he lives and they'll be visiting him soon. Great. I've only got liability on this because I just added it to the policy and don't drive it too much yet. So hopefully he has insurance and I can get a new hatch door aith a wiper that works, and a new, prettier bumper. And maybe we can swing a paint job into the deal as well.

All in all, a sucky end to a great weekend. Its not really all that bad...the guy hit me hard and we barely budged, I was impressed. So, anyone know where I can get a used rear hatch door for an '85 300TD? The guy at the body shop is having trouble locating one.

Thanks for reading, if you made it this far!
-Geoff

TWeatherford · #2 01-29-2007, 11:43 PM

The best I logged in my CD was 28 mpg, and its lighter than your wagon so I guess thats right on. Problem is, now my driving habits have gotten really bad and I have to work to keep it under 90, I'm lucky to get 22. I too have 44 psi max tires but have always kept them at the MB recommended pressure, 28 on the front and 32 on the back.

pawoSD · #3 01-30-2007, 12:05 AM

Those engine temps are too high, I'd say you probably need a new radiator or thermostat. In my case it was the radiator...temps dropped down significantly. In those same conditions as you were in, my car barely hits 80C, with my old filthy radiator it'd have been around 88-90C.

Sorry to hear what happened

I am always afraid to think of what I might do to someone if they hit my car like that...

At least I don't carry any weapons....

barry123400 · #4 01-30-2007, 11:15 AM

Sad ending to an nice trip. It would be nice if he had insurance but I would not hold my breath. To drive away like that is not too promising. Perhaps he owns his own house. If so and being older the house might be paid down and you may still come out okay.
You might ultimatly have to have him convicted for leaving the scene of an accident to stand a chance though. Hope the police are helpful. Retain a sample of paint from his car if you have one. One source for the rear door might be one of the larger mercedes parters. Also check to see if a member is parting one at present by posting in parts wanted. I seem to remember something.....

winmutt · #5 01-30-2007, 11:26 AM

95C is about what i get on my '80 wagon.

Ether · #6 01-30-2007, 11:29 AM

Quote:

Originally Posted by pizzachef

Next, the mileage I got, averaging 65-70 mph, was around 27mpg, but adjusted for the 12% offset in the speedo, that brings it down below 24mpg. Are others getting better? I had the tires inflated to their recommended max of 44psi...it was a bumpy ride in some places.

Just because your speedo is off does not necessarily mean that the odometer is inaccuarate as well. Did you check your odod against a known distance?

vstech · #7 01-30-2007, 11:42 AM

Quote:

Originally Posted by pizzachef

So the first thing that I noticed is that the speedo is about 12% faster than what the gps says. The car's got 195/70R14's, is that the right size tire?

no, the correct tire is impossible to find, that size is close enough. I think 185 70/14 is closer, but that size would lower the speedo, not raise it. you must have a changed speedo from either a gasser, or your rear dif was changed from one in a 240... very odd.
John

SwampYankee · #8 01-30-2007, 11:44 AM

That sucks, chef. I can't really offer much as I haven't been able to log any highway trip more than 50 miles so far, but wanted to send our best wishes to a fellow wagoner. Mine does hover right around 80C all of the time, though.

Good luck with everything!

SwampYankee · #9 01-30-2007, 11:50 AM

Quote:

Originally Posted by pizzachef

So the first thing that I noticed is that the speedo is about 12% faster than what the gps says. The car's got 195/70R14's, is that the right size tire?

FWIW-one of my salesman bought a brand new '07 VW Jetta and noticed that the speedo was about 10% off from what his GPS logged, which he 'confirmed' with one of those radar trailers that show you your speed in construction zones. He contacted his dealer who told him that seemed about right?

I told him to check some VW forums to see if that was common but he hasn't gotten around to it yet.

vstech · #10 01-30-2007, 11:56 AM

if you visit NC much, I will have several TD's parted out soon. maybe by this time next year...
I work fast.

John

Brian Carlton · #11 01-30-2007, 11:57 AM

Quote:

Originally Posted by pawoSD

Those engine temps are too high, I'd say you probably need a new radiator or thermostat. In my case it was the radiator...temps dropped down significantly. In those same conditions as you were in, my car barely hits 80C, with my old filthy radiator it'd have been around 88-90C.

The variable that you're missing is the ambient temperature. At temperatures below freezing, the old radiator will do perfectly fine to get rid of any heat asked of it. A brand new radiator will run the identical engine temperature.

Now, if the ambient temperature is 80F., you've got a completely different set of variables. You can condemn the radiator if you wish under these circumstances if the engine runs hot.

In this case, the only possibility is an error in the dash gauge or a thermostat that needs replacement. I'd place my bet on the former due to personal experience with the SD.

lkchris · #12 01-30-2007, 01:00 PM

195/70-14 is the correct tire size.

It is INCORRECT to assume that if the speedo provides an erroneous speed reading that the odometer is off as well.

Germans intentionally build in error to ensure the speedo does not read a lower speed than you are actually running. They call it speedometer "advance."

Here's what BMW states in a motorcycle service information bulletin:

Quote:

Speedometer advance is necessary to compensate for the negative tolerances in tire sizes between tire manufacturers, electric speedometer indication, and other factors. This advance reduces the risk of the speedometer displaying a speed that is less than the vehicle’s actual speed. The maximum amount of speedometer advance is 10% of the vehicle’s actual speed plus 2.4 mph.

dmorrison · #13 01-30-2007, 01:21 PM

Sorry to hear about the accident. Get copies of all police reports and if the guy hesitates to pay up, press charges and get a lawyer.

Iv'e owned my 82 300TD since 1990. I average about 24 MPG so your not completely off.

Test your speedo with either one of the radar speed detectors on the side of the road. Here in Texas they are putting the speed readouts just as you enter school zones here. Texas is VERY serious about school speed zones. Everyone will slow to 20MPH BEFORE entering the zone. Fines are very very heavy.
Or get on the highway. Do exactly 60MPH and time yourself between 2 mile markers. It shoudl take exactly 60 seconds between the 2.

44PSI is high based on Mercedes info. I run ar 32psi on all 4 tires. Which is still high.

The engine temp is a little high. Based on the outside temp, the cooling system should be able to maintain the 80C area. Try a IR temp gauge and see what the radiato is doing temp wise. If the radiator is clogging up. The IR temp sensor will be able to determine that. If its OK test the thermostat in a pan of water on the store with a thermometer. It should be fully open at
80C. If bad replace it.

Dave

pizzachef · #14 01-30-2007, 01:59 PM

Quote:

Originally Posted by lkchris

It is INCORRECT to assume that if the speedo provides an erroneous speed reading that the odometer is off as well...

O, I made a bad assumption. I figured since they are both driven by the same cable, they would both be off about the same. I've never heard of speedometer "advance". I will definitely do a distance check between mile markers on the interstate to verify the odometer reading.

As for the thermostat, I just replaced it, and after a flush of the cooling system in the spring, if the temps are getting high, I'll plan on replacing the radiator.

The tire pressure I will probably lower because it seemed to be putting a lot of vibrations into the suspension that I assume wasn't intended in the original design, besides, the mileage didn't go up that much anyway.

VSTECH,
I may be contacting you if my mechanic can't find a rear hatch door, i'm hoping this all gets covered by the nimrod's insurance, so we ought to be able to pay for shipping charges. But I'll post in the parts wanted section first, see if I get any leads there.

Thanks everyone for the advice, I really appreciate the help.
-Geoff

captainmonk · #15 01-30-2007, 02:33 PM

dont wait on vstech those carolina boys move slow and besides like me he is always here unless he has a laptop on his fender.......... well you know