On the W124s I've owned, including one with 606 engine, I've never had any trouble filling the entire cooling system through the expansion tank. Coolant eventually made it to the upper radiator hose and then I would proceed to get the coolant into the heater core.

On my 98 E300 (W210 chassis, 606 engine), I drained out seven quarts or so. Then, after putting in approx. four quarts, the level in the expansion tank doesn't seem to be going down. The car is on level ground....the same spot where I've successfully filled other systems.

I don't mind taking a long time...that's why I didn't disconnect upper radiator hose and first fill from there.

Am I doing something wrong? Why do I do next? Is it safe BRIEFLY to start the engine?

Thanks.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Go ahead and start the engine, and once the thermostat opens, things will speed-up......

What is your fear of backfilling the upper radiator hose?

No fear… But I thought why disturb something that doesn't need to be disturbed? I'm not in any rush.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

No.
There is nothing wrong with how you do this.

IMO: It is the slow/hard way = you trap more air in the system, and require more effort/time burping = if time does not matter, that is OK.

As a professional mechanic, the customer is charged for every moment = I save them on average half an hour = less money by bleeding the cooling system faster.

**********************

Back filling through the engine is easier/faster...

When the repair is done:
Disconnect the upper hose from the radiator, use it to reverse fill = coolant in through the engine block and out the upper radiator fitting.

There will still be minor burping in the first thirty miles of driving, typically between one pint - quart.

.

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Plus I've always had a perfectly easy time of it filling through the expansion tank.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Well, go ahead and start the engine and fill as the engine's cooling system draws down on the expansion tank.

I had more of a fear of something gettiing blown-out in the system somewhere with the excess air being pressurized. Water doesn't compress as air does, so, the common sense approach to filling my cooling system to avoid creating problems is what I went by.

On my '97 there is a air bleed bolt located between the fuel filters and the valve cover. It is a large hex head bolt that can be unscrewed to bleed air when filling with coolant. I assume your '98 would be the same.

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'97 E 300 D

These cars are a little more slower to fill versus the w124 606 model. As already stated either be patient or crank it up and fill it as level drops if you are in a hurry.

__________________
Jim

Here is the bleeder, in the centre of the picture. Mine is a 98 as well.

Attached Thumbnails

 

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

I went through this same thing not too long ago. Long story short... Injustbtook a long time for it to get up to thermostat opening temp just Idleing in the garage. After it did it was just like normal filling through the expansion tank.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

That fill hole was dropped before 99 MY production and I believe part way through the 98 MY.

Owning a 99, I always filled the block though the upper rad hose first. Then the fill tank/radiator and finally topping off after the thermo opened and it had burped a few times.

Pays to check it a few days later just to be sure.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

After letting engine idle for 5-10 minutes, temp got up to 65 or so but no drop in level. So I cut to the chase, filled through upper rad hose, and things progressed pretty quickly after that. So, at least with this car, that's how I'll have to do it.

Thanks for the help.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife