citric acid and the heater core. - PeachParts Mercedes-Benz Forum

300DPETE · #1 11-06-2005, 11:38 PM

Does anyone know how well flushing with citric acid cleans out the heater core? I was thinking of replacing mine as a preventative measure (still works), but didn't know if a citric acid would clean this sufficiently. I figure after 24 years, it's probably not super clean inside.

Also, how hard is it to replace? (other than having to shill out $300).

Brian Carlton · #2 11-06-2005, 11:49 PM

Citric acid will clean the entire system and remove the accumulated rust.

However, the heat offered by the heater core is usually sufficient despite the condition of the cooling system. It doesn't make a lot of sense to do a citric acid flush for the benefit of the heater core. If you have overheating problems and suspect accumulated rust in the block and corrosion inside the radiator, then the procedure makes some sense.

It's not a panacea, however. Sometimes the components need replacement and the citric acid simply won't cure the problem.

300DPETE · #3 11-07-2005, 12:04 AM

Quote:

Originally Posted by Brian Carlton

Citric acid will clean the entire system and remove the accumulated rust.

However, the heat offered by the heater core is usually sufficient despite the condition of the cooling system. It doesn't make a lot of sense to do a citric acid flush for the benefit of the heater core. If you have overheating problems and suspect accumulated rust in the block and corrosion inside the radiator, then the procedure makes some sense.

It's not a panacea, however. Sometimes the components need replacement and the citric acid simply won't cure the problem.

Ahhhh. I'm clueless enough that I thought that the engine coolant circulated throught the heater core and that inturn, you'd be reconditioning the heater core with a citric acid flush of the coolant system.

Thanks.

P.S. No known problems with the heater core so far, and the cooling system works fine. I'm just thinking of replacing it as a preventative measure so I don't have to think about it for as long as I own the car.

Brian Carlton · #4 11-07-2005, 12:28 AM

Quote:

Originally Posted by 300DPETE

Ahhhh. I'm clueless enough that I thought that the engine coolant circulated throught the heater core and that inturn, you'd be reconditioning the heater core with a citric acid flush of the coolant system.

Maybe I've misled you.

You are definitely correct in your analysis. If you perform a citric flush, the acid will have a beneficial effect on the internal passages of the heater core.

However, my comments are that the heater core can function well even when it is not in perfect condition. If the remainder of the system is marginal then it makes sense to perform the flush, which will also serve to flush the heater core.

But, if the system is working well, it does not make sense to go through the effort of a citric acid flush and/or replace the heater core.

Would you make the effort to replace the evaporator just because it is old? Now here is a component that could use a good cleaning. But the cost and time is very high.

300DPETE · #5 11-07-2005, 12:36 AM

Quote:

Originally Posted by Brian Carlton

Maybe I've misled you.

You are definitely correct in your analysis. If you perform a citric flush, the acid will have a beneficial effect on the internal passages of the heater core.

However, my comments are that the heater core can function well even when it is not in perfect condition. If the remainder of the system is marginal then it makes sense to perform the flush, which will also serve to flush the heater core.

But, if the system is working well, it does not make sense to go through the effort of a citric acid flush and/or replace the heater core.

Would you make the effort to replace the evaporator just because it is old? Now here is a component that could use a good cleaning. But the cost and time is very high.

Agreed, but luckily that's been replaced (the evaporator and other AC components by the previous owner). If I replace the heater core, I essentially have a new climate system, both hot and cold.

As for the engine coolant system needing a citric acid flush, when I recently installed an inline block heater (in the hose running from the bottom of the radiator to the thermostat housing), I noticed a substantial amount of rust in the old hose, so I thought a citric acid flush was in order. I'll also be changing out the water pump, monovalve, and thermostat while I'm at it.

Brian Carlton · #6 11-07-2005, 12:40 AM

Quote:

Originally Posted by 300DPETE

As for the engine coolant system needing a citric acid flush, when I recently installed an inline block heater (in the hose running from the bottom of the radiator to the thermostat housing), I noticed a substantial amount of rust in the old hose, so I thought a citric acid flush was in order. I'll also be changing out the water pump, monovalve, and thermostat while I'm at it.

I had a decent amout of rust on the top hose for the SD. But, the coolant that exited the block had no rust in it, so I'm not too worried about it. I think the citric acid flush should be reserved for those cases where the system has been neglected for many years. There is quite a bit of effort involved in eliminating all the acid after introducing it into the system. Furthermore, I understand that a degreaser is required before the introduction of the citric acid. It's quite an involved process.

300DPETE · #7 11-07-2005, 12:44 AM

Quote:

Originally Posted by Brian Carlton

I had a decent amout of rust on the top hose for the SD. But, the coolant that exited the block had no rust in it, so I'm not too worried about it. I think the citric acid flush should be reserved for those cases where the system has been neglected for many years. There is quite a bit of effort involved in eliminating all the acid after introducing it into the system. Furthermore, I understand that a degreaser is required before the introduction of the citric acid. It's quite an involved process.

Good food for thought, thanks Brian.

I have the Palmolive and citric acid powder ready to go, but maybe I'll wait and see what the condition of the water pump is before I do it (the pump probably being a good indicator of the coolant system condition, no?). Is there any harm that can be done with the citric acid flush, as long as you flush the acid four or five times with tap water after doing the flush?

Thanks,

Pete.

Brian Carlton · #8 11-07-2005, 12:57 AM

Quote:

Originally Posted by 300DPETE

Good food for thought, thanks Brian.

I have the Palmolive and citric acid powder ready to go, but maybe I'll wait and see what the condition of the water pump is before I do it (the pump probably being a good indicator of the coolant system condition, no?). Is there any harm that can be done with the citric acid flush, as long as you flush the acid four or five times with tap water after doing the flush?

I just replaced the pump on the SD as a preventative measure. The original pump was an OE pump, so, I presume it was original. Didn't appear to have any corrosion issues and the bearings were OK, so it probably could have went a few more miles. But, the SD got the full treatment over the last few months, so, the pump was on the block.

Nope, no harm in doing the flush if you don't mind spending the entire day at it. I would drive it for a few hours with the acid in the system. The heat must be set on high. When you flush out the acid, you will need to drive it and get the coolant flowing through the heater core, on every flush, so it's a long tedious process.

I don't believe that you can properly flush the acid without actually driving the vehicle with the heat wide open.

300DPETE · #9 11-07-2005, 01:29 AM

When you finish the acid flush, and are ready to clean it out with water four or five times, how long do you need to run it on plain water each time (for each of the four or five times) before you fill up with 55/45 coolant? I was set to drive a few hours on the citric acid, but thought that after, all I had to do was run the car at operating temperature for 10 minutes or so for each of the 4-5 water flushes to get the acid out. Am I wrong?

Pete.

Brian Carlton · #10 11-07-2005, 09:21 AM

Quote:

Originally Posted by 300DPETE

When you finish the acid flush, and are ready to clean it out with water four or five times, how long do you need to run it on plain water each time (for each of the four or five times) before you fill up with 55/45 coolant? I was set to drive a few hours on the citric acid, but thought that after, all I had to do was run the car at operating temperature for 10 minutes or so for each of the 4-5 water flushes to get the acid out. Am I wrong?

Pete.

It's just my opinion, but I would think that 10 minutes at full operating temperature would allow the water to mix with whatever remaining liquid is in the system.

BTW, you can become much more efficient with the flushes if you utilize the block plug. It's a PITA to get to, but the entire lower block, below the thermostat, is filled with coolant, even when you drain the radiator.

300DPETE · #11 11-07-2005, 09:42 AM

Quote:

Originally Posted by Brian Carlton

It's just my opinion, but I would think that 10 minutes at full operating temperature would allow the water to mix with whatever remaining liquid is in the system.

BTW, you can become much more efficient with the flushes if you utilize the block plug. It's a PITA to get to, but the entire lower block, below the thermostat, is filled with coolant, even when you drain the radiator.

Anybody have a picture of where the block plug is on a 617?

Brian Carlton · #12 11-07-2005, 10:08 AM

Quote:

Originally Posted by 300DPETE

Anybody have a picture of where the block plug is on a 617?

There is one floating around here somewhere.

But, if you go underneath, find the forward end of the starter, go forward about three inches and up about 1 inch there will be a bright hex plug that sticks out from the block. That's the plug. It appears to be quite high on the block. Don't be confused by that.

boneheaddoctor · #13 11-07-2005, 10:55 AM

Quote:

Originally Posted by 300DPETE

Anybody have a picture of where the block plug is on a 617?

Its just behind the passenger side engine mount....easier to reach on some models than others...forget its size but is likely a 13 ir 14 mm hex head plug.

funola · #14 11-07-2005, 11:00 AM

What's a good source for this citric acid? Is this concoction sold as a coolant rust removal agent? What about Prestone collant system flush? What's the active ingredient?

boneheaddoctor · #15 11-07-2005, 11:06 AM

Quote:

Originally Posted by funola

What's a good source for this citric acid? Is this concoction sold as a coolant rust removal agent? What about Prestone collant system flush? What's the active ingredient?

DO what I do...look on ebay.....find a few guys who need to do the same thing and split the costs with them....you need 2.2 lbs per car...

Citirc acid is eviromentaly safe...is used in food and soap.....