Did citric acid flush with extra care, now leaking ... braze or replace? - PeachParts Mercedes-Benz Forum

samboyellowsub · #1 07-06-2010, 08:00 PM

I decided that it was time to do a coolant system flush on the 82' 240D. I've driven the car for about 5 or 6 years and the more I learn about the car, the more it became important to me to flush the system which I have not seen done in the 7 years its been in the family. A couple months ago I did just a simple water flush initially and ignorantly filled up on the green stuff/water and this past week I brought out the big guns.

I removed the thermostat last thursday (thats how long I've been doing it to make sure it is thorough) before I started anything and then cleaned out everything with hose water until it ran clear. Then did a Prestone flush because I got an unopened bottle for $1 at a flea market. That loosened a lot up then I ran it clear. Then I used about 20 ounces of original Dawn mixed with water and ran it for an evening of errands and then some the next morning. It also loosened a lot of stuff. I ran it clear and flushed for about 15 minutes. And did several errands on just water and stuff was still coming out when I drained/flushed the system. Did a few flushes like that - don't remember how many. Every other flush, I drained the block too.

Then I used a kilo of food grade citric acid dissolved in water and ran it for about 25 minutes. Some on idle and some running up and down the street. That was Saturday, I think. I drained and flushed the whole system (block plug too) like crazy, back and forth, then immediately I started a series of water fill ups, run for half a day, and then drain and flush. Last night on after about the umpteenth flush with a garden hose, the radiator developed a pinhole leak. I drove around all day Monday with absolutely no leaks whatsoever. In fact ever, since I've driven the car, it has not once leaked a single visible drop of coolant. I'm not mad at myself really for doing it, but I'd like some input if there is anything that I obviously forgot to do?

Mainly I'd like input on whether I should replace that radiator or take it to a shop and have it repaired - I guess they'd braze it. I don't want to put a StopLeak in it - that would negate all the effort I just put into it.

As far as I can tell, neither the driver or passenger heater cores are leaking.

What to do ...

samboyellowsub · #2 07-06-2010, 08:10 PM

I almost forgot the weirdest part ... it only leaks after the water has cooled back down in the radiator. The thermostat is still out.

Chas H · #3 07-06-2010, 08:24 PM

Running without the t-stat can cause the engine to overheat because the radiator by-pass is not closed as the engine warms. The 28 yo radiator is likely done for if citric acid flush is gonna cause leaks.

samboyellowsub · #4 07-06-2010, 08:33 PM

Quote:

Originally Posted by Chas H

Running without the t-stat can cause the engine to overheat because the radiator by-pass is not closed as the engine warms. The 28 yo radiator is likely done for if citric acid flush is gonna cause leaks.

explain.

Do you mean, that it does not allow the engine to warm up quickly since water is being immediately circulated to the radiator?

Chas H · #5 07-06-2010, 08:43 PM

Quote:

Originally Posted by samboyellowsub

explain.

Do you mean, that it does not allow the engine to warm up quickly since water is being immediately circulated to the radiator?

The t-stat has a valve on its base that closes a radiator bypass as the engine warms and the t-stat opens. With the t-stat absent, coolant can bypass the radiator and cause overheating. Look at your t-stat and the housing it lives in. I don't have a diagram at hand to post for a better explanation, maybe another reader can do it.

vstech · #6 07-06-2010, 08:43 PM

with the thermostat out, the water does not go to the radiator at all. thus you can overheat very quickly. the thermostat forces water into the radiator when it opens.
yes, the citric will find any weak spots that exist in the radiator. if it leaks after a citric flush, then it was due to fail anyway.

samboyellowsub · #7 07-06-2010, 09:16 PM

Quote:

Originally Posted by Chas H

The t-stat has a valve on its base that closes a radiator bypass as the engine warms and the t-stat opens. With the t-stat absent, coolant can bypass the radiator and cause overheating. Look at your t-stat and the housing it lives in. I don't have a diagram at hand to post for a better explanation, maybe another reader can do it.

I didn't know that.
Thats weird. Since I've been running without it, the temp has pretty much settled at 80 once it warms up.

Even more strange is that it only leaks when it cools back down. Can anyone explain that?

tangofox007 · #8 07-06-2010, 09:41 PM

Quote:

Originally Posted by vstech

with the thermostat out, the water does not go to the radiator at all.

With the paths to the radiator and the bypass completely unobstructed, it does not stand to reason that all the coolant would take the bypass route.

samboyellowsub · #9 07-06-2010, 09:59 PM

Quote:

Originally Posted by tangofox007

With the paths to the radiator and the bypass completely unobstructed, it does not stand to reason that all the coolant would take the bypass route.

That's exactly what I thought. From what they were saying it sounded like the radiator would be blocked somehow without the t-stat.

vstech · #10 07-06-2010, 10:06 PM

true, but if there is no door forcing one or the other, the system never pulls correctly from the radiator, and the bypass is the path of least resistance, and can cause an overheat from improper flow.

samboyellowsub · #11 07-07-2010, 11:03 PM

Update:
I took the radiator out to find the leak and was hoping to braze it. I took it to a shop where the guy happened to be there while he was on vacation. While he was unsuccessfully trying to braze it and burning holes in it, he asked me what I could get a new one for. I told him $180 shipped. He told me he'd sell a new one for $150 cash right there. It was for someone who ordered it and never picked it up. It was a few inches longer on the passenger side, but everything else looked like it lined up up just right. luckily i don't have a transmission cooler so the extra length wasn't a problem besides needing to modify the fan shroud slightly. It actually was about a centimeter longer on the oil cooler side so it was a tighter fit there but it worked and doesn't rub on the body.

So, about this radiator ... besides the width being longer. The core is black, it is definitely a copper or cuprous core because its about 3x heavier, made in holland, and it seemed to just drop right into my engine bay all the hoses were in the same spot too. It had two covered metal threaded ports on the bottom plastic portion. Does anyone know what this actually was made for?

Just curious.

BTW running air through my radiator in a bath revealed that it was like swiss cheese, holes everywhere. Before Monday, it never leaked one drop in seven years. wow.

vstech · #12 07-07-2010, 11:27 PM

well, for comparison, when I did the flush in my aluminum radiator equipped 82SD after the block flush, and system flush with garden hose for 30 minutes, draining, tide detergent flush, and then rinsing that well, I put in the citric flush, 2.2 lbs (1KG) dissolved in distilled water, and filled with distilled water, then drove around for 2 days... then flushed again, and flushed and flushed, got all gunk out of the block and the radiator. 2 years later, system still no leaks.
it's all about the condition of the system prior to the fllush. the flush will find flaws it will not create them unless you leave it in too long.

samboyellowsub · #13 07-07-2010, 11:36 PM

Quote:

Originally Posted by vstech

the flush will find flaws it will not create them unless you leave it in too long.

Yeah, i figured that the only reason all those leaks came up was because the flush move what was blocking them before, even more because it only leaked when it cooled down, which told me the leaks were all so small that they were being blocked by rust and sludge.

... but does anyone know what kind of radiator I was decribing?