Citric Flushes in Older Cars. - PeachParts Mercedes-Benz Forum

jt20 · #1 05-08-2008, 01:21 PM

By reading the post below:
http://www.peachparts.com/shopforum/showthread.php?t=204502&highlight=citric+acid

-it seems that the Citric Acid Flush (caf) is more dangerous than necessary for engnes with unknown maintenance histories due to potential leaks and failures.
"...it is like putting acid in your engine", - it is putting acid in your enigne.

What are the REAL benefits of this flush (besides at proper intervals) - how much can cooling capacity really change? I doubt many are racing these cars.

once a system is well burped, how can corrosion be aggravated?

Can frequent successive flushes replace an immediate sequence of harsh flushes?

ps-- I have a car w/ unknown history which has probably been drained for over year and now has green stuff in it.

vstech · #2 05-08-2008, 01:42 PM

...
properly done, citric flush should not affect a decent vehicle.
that said, if the car was not maintained, and there are weakness in the system, citric will find them.
I prefer to find problems in my garage, not on the road. citric flush is not a regular maintenance item, it's a repair solution.
it takes several days for citric acid to substantially affect base metal. and it attacks scale and loosens rust sediment quickly. it must be done properly, not left in the system, and complete and total rinsing is important.

... green coolant does not bode well for the proper maintenance history of your vehicle.

jt20 · #3 05-08-2008, 01:46 PM

There should be no reason to 'repair' slight surface corrosion in the coolant passageways - correct?

better yet - what is there to 'repair' by CAF?

Alastair · #4 05-08-2008, 02:07 PM

Quote:

Originally Posted by jt20

There should be no reason to 'repair' slight surface corrosion in the coolant passageways - correct?

better yet - what is there to 'repair' by CAF?

It'll clean the scale out of the smaller passages especially in the rad and the small pipe from head to block etc on the 617....

What is it with 'Green Coolant' that worries you...?

Most if not all coolant/antifreeze here in the UK is 'green' in colour...

jt20 · #5 05-08-2008, 02:15 PM

I was just using that as a generic reference (green stuff) to the degree I wish to clean, since I will put in the G-05 - I am not terribly concerned, as I have let it sit for quite some time.. but I would like to set it up so that I can leave it alone for the recommended interval, however.

I ma putting in a new radiator (used - but fair enough inside) When people refer to 'scale' is that another term for corrosion?
Is there is a reasonable means of determining the severity of corrosion / scale (ie.. "it looks clean enough to me")

vstech · #6 05-08-2008, 02:20 PM

scale is sediment from the liquid poured into the cooling system. not corrosion. usually lime from the tap water most use... which is why most recommend distilled water use in the mix.

LUVMBDiesels · #7 05-08-2008, 07:52 PM

On the 300SD I did a full citric acid cycle last spring. The car had been running at 100+ degrees even in the winter so I wanted to flush the system. It worked real well. In fact it cleaned up gunk that had been blocking a couple pin holes in the radiator! $200 for a new radiator later the tems were at 85. I do not regret doing it as it revealed a problem that would have gotten worse in the end anyway.

I would not do one every year, but I am planning on doing the SDL before summer.

PS anybody want a brand new SD rad?

anghrist · #8 05-08-2008, 08:29 PM

Okay, it's not that urgent, but this is still the best way to flush a system.

Here's what to do:
1) Order Food Grade Citric Acid
2) Buy several gallons of Distilled Water (Don't use tap water to mix the Citric as it will not go well for you. Look up chalk)
3) Get a couple of Clean 5 to 8 gallon buckets to mix your Citric Acid in
4) Buy some de-oil/degreaser flush at your auto parts store.
5) Obtain some MB-Spec Coolant
6) Break out your garden hose, drain pan, and get ready to get dirty.

The proceedure should go as follows:

1) Drain Coolant (Please make sure you know where your fill/drain plugs are first)
2) Into a Cool engine, fill with tap water.
3) Drive (get the temp up and keep it there for 20 mins, this proceedure will be refered to as flush from here on)
4) Let cool (unless you really like to scald yourself)
5) Drain
6) Tap water flush/cool/drain
7) Fill with de-oil/degreaser & distilled water, flush/cool/drain
8) Tap water flush/cool/drain
9) Tap water flush/cool/drain
10) Fill with citric/distilled water flush/cool/drain
11) Tap water flush/cool drain
12) Tap water flush/cool drain
13) Fill with citric/distilled water flush/cool/drain
14) Tap water flush/cool drain
15) Tap water flush/cool drain
16) Fill with proper mix of MB-Spec coolant and distilled water.
17) Take a shower, you're filthy and you smell funny
18) Properly dispose of all fluids. (Varies according to local laws)

It takes a while so I recommend insertining a step #) Enjoy a beer only when safe and appropriate *Don't drive if # Beer steps exceeds legal/personal limits*

If the flush reveals any leaks or other issues, then you were going to have to fix those sooner or later. It's better to have the car running cool and correctly than to avoid the repairs.

jt20 · #9 05-08-2008, 08:38 PM

Despite the wonderful directions - thank you - it still seems incredibly pointless unless I know there is an issue.

I would like to know why I am going to drain and fill and warm and dump 6 %^&& times to 'clean' the block and radiator.

if scale and corrosion are not obvious by inspection, and my engine does not overheat - why wast my time and potentially destroy the finer components of the heating/ cooling system?

anghrist · #10 05-08-2008, 10:16 PM

Sorry, but I live in the desert, so even a properly functioning cooling system can barely keep a W123 in proper temp out here. I'm just a bit proactive in keeping them running.

lietuviai · #11 05-08-2008, 11:27 PM

It's very difficult to flush the block without removing the block drain plug.
I certainly wouldn't try that on a hot engine because of the location of that damn plug.

#12 05-08-2008, 11:40 PM

After plenty of messing around, I happened to break my plastic radiator connection and bought a new radiator; cooling problems solved, my operating temperatures dropped by about 5-10C.

jt20 · #13 05-09-2008, 10:33 AM

appears that the consensus here is to PRE-emptively fail the failings on my car so that happen at a time when when I can cuss, and no one gets hurt.

I found some citric acid - only a pound. We'll see what happens. And I have a rusty head from a 240d that I am going to do a an explicative w/ pictures about this on.

LUVMBDiesels · #14 05-09-2008, 10:52 AM

Quote:

Originally Posted by lietuviai

It's very difficult to flush the block without removing the block drain plug.
I certainly wouldn't try that on a hot engine because of the location of that damn plug.

That is why I rigged up the following

I took a 1/4 inch galvanized nipple 1/4 x 2 inches. I screwed that into the block drain hole. Then I took a 1/4 90 degree elbow and put that on the end of the nipple. I then ran a four inch nipple 1/4 x 4 inches from the elbow. I screwed in a 1/4 inch ball valve then a 1 inch nipple. This way I could simply open and close the valve to drain the block. Just watch the front suspension -- on the W126 this worked great, I am not sure about clearences on a W123. When I took the car out for a spin, I also capped the nipple with a 1/4 inch end cap.

When I wanted to back flush, I would attach a piece of garden hose to the end nipple with a hose clamp. Attach the other end of the hose to the garden hose and flush away.

When I was ready for the final fill, I removed the rig and put the drain plug back.

Hope this helps!

BillA · #15 05-09-2008, 11:02 AM

I did a flush @ 150k, and 2 days later replaced the rad. Temps did not drop until I replaced the temp sender (still covered with scale despite the treatment).