I had to refill my coolant tank every other day with about 3/4 gallon of coolant. I couldn't tell where it was leaking and there was no coolant in the oil. I also didn't smell coolant or have white smoke.

I just want to confirm that my engine is not a rod bender. ANyway to confirm?

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1994 S350D
1995 E300D
1997 E300D

Auto parts stores often have pressure testers in their line-up of loaner tools. Leaks don't hide well in the face of 15-20 psi.

yup.
pump that sucker up to 22 and watch where the coolant goes...

if it's not leaking on the ground after repeated pumps, drain your oil, and leave the plug out...
see if water seeps out the drain...
it could also be going into the trans cooler, so keep an eye on that level as well.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

There's no connection between bending rods and coolant loss/consumption.

When you pressure test the system, pressure test the cap as well. For the relatively low cost, buy a new 1.4 bar cap and see if that sorts the coolant loss.

Sixto
87 300D

Cooling System Pressure Tester Kit

.

The three auto parts stores didn't have a cap that would fit on my system. Im going to bring the radiator to a shop and see if they can pressure test it off the car.

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1994 S350D
1995 E300D
1997 E300D

I'd hold off having the radiator tested independently. You want to test the entire system and it's impractical to test the rest of the system without the radiator. If you're in the US, Call Phil for a pressure cap if you can't find one locally.

Do you smell coolant in the cabin?

Sixto
87 300D

I already brought it to a local guy. There was a crack at the top right of whereb the upper hose connects. He is going to replace the side tank and boil out the radiator. The tank costs $46 and the labor is $75,

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1994 S350D
1995 E300D
1997 E300D

Keep an eye on the radiator. There general sense around here is that the radiator core doesn't take kindly to crimping onto a plastic end tank a second time.

Sixto
87 300D

Hey sixto, I wanted to let you know you were right on here regarding fixing the radiator. The rad split within 2 hours of running time. I shouldn't have felt like I owed the local guy my business to repair it and should have just purchased a new one!

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1994 S350D
1995 E300D
1997 E300D

+1 on the pump up the pressure test

John and I had just got the 300TD system together, we put the tester on it and it was slowly bleeding down.

Looked under car saw a steady drip looks like from the evap drain. Oh no.

upon closer inspection it turned out to be the aux water pump (it's on the driver side under the washer tank on a 87 300TD).

We had just replaced the aux pump with one from a p-n-p. We took the housing off to check the condition of the impeller. When we put it together the o ring was not in the right spot.

Put it back together right and she is all good now. I was sweating it thinking I would be tearing out the dash again.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech