It has been a while since I have posted on here but here is some data. For several months I was checking my mpg and getting 22-23 in town constantly and engine power was a hit or miss...in hindsight it did often feel like it was under a load constantly. Then one day I heard scraping from back right wheel well. The caliper had seized up and the outside wore the pad down and got into the rotor a bit! That same caliper was replaced one year prior.

I replaced the caliper and pads from local parts place which has lifetime warranty and now I have been getting 25-26.5 with the same kind of driving. Nice huh?

Next thing. I still have a coolant loss issue. No sign of cracked head...I have been paranoid but I have somehow convinced myself that it is okay. I am seeing no signs of leakage anywhere. Not seen any white smoke. During summer and A/C it would hit 105+ at times but not it is cooler out and it is at the 85 mark though after a quick acceleration it will rise a bit. I am thinking I have a loose hose or something.

Where else should I check?

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

The cap on the expansion tank may have weakened, and is causing a bit of evaporation. This would allow the level to go down but would likely not show-up as an actual leak. No puddle etc.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

If the coolant isn't leaking on the ground, the windshield isn't fogging up with a film when you use the defroster, and you don't smell that odd coolant smell around the engine or in the cabin ..... well the coolant isn't disappearing .... it must be going somewhere .... most likely into the engine past the head gasket or a crack in the head. You generally can't see small cracks in the head since they are on the underside of the head between coolant passages and cylinders. There is another remote possiblity .... the fuel heater. The fuel heater uses coolant under pressure to preheat the fuel before going into the injection pump .... if the heater is bad then coolant could be forced into the fuel and then ingested by the engine. My 1987 was slowly eating fuel at around 110,000 miles over about a year so I took it to a dealer to have the "professionals" figure out the problem. They said everything checked out fine .... so I took the car on a 2,000 mile road trip .... of course it only made it about halfway when it began overheating .... coolant was way down and I had to keep filling it up just to limp into a dealer .... who checked it out and cirmised it was a blown head gasket. They took off the head and unfortuantely for us found a very small crack on the underside of the head. We left the car with them and flew home. They ultimately found a used head and reassembled everything ... some three months later we flew back to pick up the car and take it for a mini roadtrip vacation home. That was about 15 years ago and the car has traveled almost 200,000 miles on that used head and hasn't lost a drop of coolant since. I suspect your problem is the same as mine was .... if you don't push it you can probably go for some time by just adding coolant every month or so .... but push the engine on a long trip or under heavy load and it could fail and leave you stranded. Sorry to add to your concerns about the issue .... but that's what happened to us. Good Luck.

Do you have the belly pan on Jon? You may not see a coolant leak with that on. VW coolant is neat cause it turns into a crusty white powder on outside of fitting when its leaking out. Easy to find small leaks at hose fittings. Can't say same for MB. But maybe there is an additive that will do that.

I've got a #14 head too. I'm in process of checking my mpg. I took my alda off and i think i am getting pretty low 20s around town when i used to get 25. But my alda was causing it to be real slow when it was first cold . Maybe not a bad thing in retrospect. But when your late you gotta go.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

I had the same problem, you just simply have to stay out of that go pedal in order for the mpg's to come back up. I know it's hard to do

OP: I have a random coolant leak that I finally tracked down to a crack in the top of the reservoir that only leaked when I parked on a slope with the nose high.

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

I swapped my coolant reservoir a few months ago when It developed a leak where the brass meets the plastic around the fill cap. I put the one in from my parts car and put a new radiator cap on it and all seems well there. The Fuel heater is bypass as far as the fuel goes and it is not leaking on the coolant side of it.

As I said, the engine runs very well but warmer than it should during the summer. At some points I must have gotten the cooling system completely sealed because the temps were tons cooler, but then something "gave" again and it became temperamental.

Also, what number head did the dealer replace yours with?

Another option I have heard of was having the CAT cut out from the exhaust system. I read one person checked and replaced everything and then cut that out and bam, everything was fine!

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

You have a minute head gasket problem, probably not cracked head. What you are experiencing is similar to my SDL which has the same engine and #14 head. The top radiator hose is rock hard in the morning when engine is cold, losing coolant about 1 quart or more per week, temperature is a tad high when climbing hill.

I put up with it and will try to fix it eventually. There should be NO loss in coolant as it is a close system. Coolant may go into the holding tank if the pressure is too high ( about 20psi ) but will be sucked back in when engine cools down ( a vacuum is created when cold ) so there should be no net loss of coolant.

Good luck.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

I have considered just that. However, my top hose is not rock hard in the morning and once I crank it up when cold, it does not become hard quickly (another sign of bad head gasket/head). Coolant loss is maybe a half gallon every month or two. When the summer was in full, I could not park my car too long with AC on idling, otherwise the temps would climb above 100.

I can hardly remember anymore all the steps I took but I had it pretty well sorted as it got cooler. Fan clutch, temp sensor, etc. From the start I replaced water pump, radiator, and later discovered a leak around water pump housing. So I yanked it all and replaced all of the gaskets again and that leak went away and temps were around 80 for a bit, then it came back and was at 85ish.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000