Hi All, I have replaced my old leaky radiator with a new Behr (by the way, it's amazing how much lower the operating temperature now is... it never gets over about 140 F!). I am also in the process of doing the De-Oiling/De-Rusting procedure. So far, after replacing the radiator, I've first flushed the cooling system with tap water (replaced the fluid after driving at operating temperature for 20 minutes) twice. Then I've done the DAWN (22 oz) degreasing flush with distilled water. Then flushed three more times. Then the Citric Acid (2 lbs. in 2 gallons of distilled water) flush.

NOW, after using the citric acid, I noticed that hose connections started leaking water - the fluid pressure inside the cooling system, after driving, was ENORMOUS, causing the fluid to burst out with incredible force when I finally opened the radiator drain plug!!! WHAT THE F@#K?!?

After that, I've done three more flushes, and on the third one I've added 1 lb. of baking soda to the water. (I still have three regular tap water flushes to go, before I finally add 50/50 Zerex G-05 and distilled water.) BUT, EVEN NOW, each time after driving the car even a few miles, pressure still build up in the cooling system, leading to the point where hose connections start leaking water... (Now that I know, I slowly open the radiator cap to let pressure out right after driving at the end of a flush).

WHAT THE HECK IS GOING ON??? Can it be the dish detergent I used when degreasing that might be still in the system? (Water still comes out slightly foamy, even after all these flushes....)

THANKS.

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

Citric acid + mineral scale = CO2 + water + salt
Kinda like the baking soda + vinegar volcano.

I just did this this weekend and noticed that for the 1st 2 flushes (with distilled water) after the citric acid I was still getting some bubbling when the draining fluid hit the puddle of previously drained fluid.
Not like soap bubbles, more like a light simmer.

I also noticed that I had quite a bit of pressure after the 1st flush. It went away by the third flush, and I haven't had any other problems since filling with coolant.

Maybe try a few more flushes?

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

... what radiator cap do you have on? it should vent any pressure above 140Kps (approx 22Psi)
but yeah, more flushes for sure!

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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!

Even a few psi will seem like a lot when you are having the drain plug blown off into your face.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Do you have pressure when cold? Try opening the cap to remove any pressure, replace it. Start the car and feel the pressure in the hose. If its hard, it sounds like combustion gases are finding their way into your cooling system (head gasket or worse).

__________________
For Sale: 1982 MB 300TD
1995 Chevrolet Suburban 6.5TD

Sold: 1980 IH Scout Traveler- Nissan SD33T Diesel

By the way, you wanted to use (non-sudsing) detergent, not soap.
Like dishwasher machine detergent.

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1982 300CD Petrol/Black Leather

The high pressure started right after the first flush with citric acid (the baking soda came in only after three additional flushes. So it has nothing to do with the baking soda itself). Besides, I used distilled water when doing the citric acid flush.

Hi John. The one you suggested a few weeks ago: a made-in-germany, brand-new 120Kps...

Yea, but not only that... After driving, if I don't take S-L-O-W-L-Y the cap off to release pressure, after an hour or two it starts leaking profusely at the two radiator hose connections... the pressure inside must build to extremely high...

Hi, I just did as you suggested. After removing the cap to relieve pressure, then putting it on and starting the car, the hardness in both radiator hoses is exactly the same (both with radiator cap off/engine off and with it on/engine running)... THANK GOD!!! And yes, the pressure stays up even when the engine gets cold: two days ago I had done the citric flush, then went back to the car three hours later, after the engine cooled off, and that's when I noticed the hoses leaking, and the fluid splashed on my face when I opened the radiator drain plug (good thing I didn't get any in the eye).

Yes, that's what I used, 22 oz of Dawn dishwashing detergent, properly diluted in two gallons of hot distilled water.

So, guys, I will keep doing additional flushes. Any other ideas?
By the way, when I drain, the fluid still comes out with bubbles, as if some of the dishwashing detergent is still in...

__________________
1979 240D, W123, 105K miles, stick, white w/ tan interior.

I meant the mineral scale in your system that you are using citric acid to dissolve....that reaction produces gas.

Are you draining both the radiator and the engine block after each flush?

so the bubbles linger and float on top of the water? FSM recommends a 5% detergent solution - that is about 12 ounces, so maybe you just put a bit too much in and it is taking longer to wash out. All the soap bubbles in my system were gone by the 3rd flush after de-oiling (before citric acid)

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

Thermostat is stuck open or missing. Replace it. Operating coolant temp should be 175F+ for the engine to seal.

I second that. 140F = 60C and is well below the 80C min recommended operating temp. You will appreciate driving in the winter with a properly working thermostat so will your rings wear the cylinder walls less when they are hot.
Are you filling the head when you add water/glycol or do you fill thru the radiator cap?
I always fill 617's thru the heater hose, the one the goes into the head to the firewall. Fill until it bubbles out of the expansion tank (if you have one, I believe the '79 does not use one by design. hint: I added an expansion tank to my '79 300TD when I upgraded to the larger radiator)
Back filling in this way will prevent air bubbles forming in the head and possible steam pockets.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

I don't think Dawn makes a "dishwasher" detergent. You need the soap for electric dishwashers, usually sold as powder or the encapsulated "pill" that is low or no sudsing.

John

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Certified Registered Nurse Anesthetist (CRNA)
2002 F250 powerstroke with Plantdrive WVO conversion
1983 300SD 190K miles ,sold
2006 E320 CDI

Blue Liquid (Same old Dawn you've used at the kitchen sink)in the opaque plastic bottle.

Not Automatic Dish-Washing Powder (Many,Too Many,Harsh chemicals)

You want to De-Oil the innards of the Cooling system...Not Acid Etch it.

Hello,Now that I mention it...How does the inside of the Cooling system get
oily ('Don't know about you,I never put a drop of lubricant in there)?

__________________
'84 300SD sold
124.128

OK, I see...

Yes, I am draining both after each flush.

That's correct. As you say, I likely used too much detergent. I'll keep flushing until the soapy bubbles are gone. I'm getting to it again later tonight.

Oh, so that's what it is... I had removed the thermostat before the de-oiling procedure as per FSM instructions (job 20-015 - Cleaning the Cooling System)... I will put back the thermostat after the flushes and before refilling with Zerox G-05/distilled water.

Could the missing thermostat have anything to do with that pressure build-up? I don't think so, because there was none when doing the flushes after de-oiling and before the citric acid flush.

See above reply in re thermostat.

When I fill, I first disconnect the upper radiator hose and top it with liquid. Then reconnect it, unscrew the vent plug and fill through radiator cap until liquid flows out of the vent hole. Then replace plug & cap. It works wonderfully - no air bubbles. (I have a 79 240D first version and it does not have an expansion tank.)

So maybe I f@#ked up... My understanding from the posts was to use Dawn dishwashing detergent in the sense of the one used to wash dishes by hand. That's what I used (not the one for electric dishwashers). What's sudsing? Did I screw up big way here?

Thank GOD! That's what I've used (Dawn blue liquid in the plastic bottle).
As to your question, I think perhaps coolant fluid has some components in it that causes oiling.

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

It could be that the operating pressure is well within normal limits and your very subjective assessment of the situation is resulting in an improper diagnosis.

When you flush the engine do this:

Goto the hardware store and buy a few 1/4 inch galvanized pipe nipples and elbows. I used a two inch nipple attached to a 90 degree elbow attached to a four inch nipple that I attached to a ball valve and finally another three inch nipple that I clamped a piece of garden hose to (with the female connector attached) to the other end of the hose.

Remove the block drain and install your galvanized gadget. Remove the radiator cap and if you still have the thermostat out, leave it out.
Hook the hose up to your garden hose and run water through the block and out through the radiator.

Start the car and run the heat on full. If you have a monovalve, unplug it so that it stays open

Run the car for 20 minutes with the water flushing.

close the valve and remove the garden hose (not the one clamped, but the one attached to your faucet).

Run the car for an additional five minutes

shut down and open the block drain valve and radiator drain.

Repeat until the water no longer feels 'slippery' or it tests neutral with a litmus strip.

completely drain the system and remove the galvanized pipes replacing them with the drain plug

run 100% distilled water for a week

drain completely

add 50% Zerex G05/50% distilled water mix

__________________
"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy"

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