Slow leak from car's A/C system

[ezzra]

My W204 MB has developed this small leak from the A/C system that was found to be under the dashboard and needed topping gas every a month or so, and to fix it will cost 17,000-20,000 baht, so I'm thinking of using the Air Conditioning MRL-3 Super Seal A/C Stop Leak Sealer STP AC PRO Air Con Fix that cost 26 GBP to try to stop the leak and save on taking the dash board apart and the cost, Thailand doesn't have that item for sale so i got it from the UK, did anyone used this remedy and did it work or have an idea how to go about fixing this issue?...

 

https://www.ebay.com/itm/273353771607

Edited November 8, 2022 by ezzra

[degrub]

Has a tech positively identified the actual leak location with fluorescent dye to make sure it is not a mis-seated connection or o-ring or vibration induced crack ?

The filling valves are a very common weep point, especially if uncapped or  missing cap o-ring.

 

They do state that if the dye is visible, the hole is too large (q&a on the Amazon listing) for the product to work. 
 

I have had rubber hoses that turned fluorescent after a few days when i could not otherwise sniff a leak. 
 

My grandfather was a commercial A/C tech and hated the stuff . Clearly, it works for some. I suspect that if you have to open the system in the future, it would have to be flushed clean to remove the residual unreacted additive in addition to the usual vacuum pump out drying and leak test. And pulling a full vacuum may dislodge the plug.

 

just a few thoughts.

 

 

[seedy]

In my experience most evaporator leaks require dash dismemberment.

PITA. Big job.

When had the CR-V in the shop they had a Lexus SUV in for the same job.

Was amazing what needed to be removed ! Nothing left from the firewall to the rear seats !

[Lacessit]

Probably easier to sell the Benz if the sealing gunk does not work, Mercedes dealerships here charge 3-4 times in servicing what one would pay for something like a Toyota.

MB has acquired an unenviable reputation for throwing their car buyers under a bus. I owned one once, never again.

[Tropposurfer]

Sorry you've got this annoying ongoing aircon problem ????

 

Is your quote from MB?

You say it was definitely found under the dash.

If this is the definitive leak point then ...

... There are some good MB independents around BKK who can help you at maybe at less cost. Sorry I can't offer a referral as I'm in Phuket.

 

My caution about any independent touching a complex, fine tolerance vehicle like a Benz is something I would not personally conscience unless you have really good long experience with that particular mob.

 

As an MB owner here myself I would say that under 1000 AUD for this dash removal fix is quite reasonable (especially if its being done by MB as you get a rock solid warranty on the work and genuine parts and MB grade gas).

 

Given the fix requires removing the entire complex dash and components to access, repair, and reassemble I wouldn't use anyone but someone with long experience, a solid well-known independent OR similar good rep Benz dealership to touch it. 

Peace of mind is also one thing I wouldn't trade off for a few hundred dollars.

 

 

[Tropposurfer]

21 minutes ago, Lacessit said:

Probably easier to sell the Benz if the sealing gunk does not work, Mercedes dealerships here charge 3-4 times in servicing what one would pay for something like a Toyota.

MB has acquired an unenviable reputation for throwing their car buyers under a bus. I owned one once, never again.

Sorry you had a bu.mer of an experience with MB Lacessit. There are lemons (even in Benz's) and bad faith dealers for sure.

I've owned them for decades (in OZ, USA, Europe and now LOS) and never had a bad car, nor a bad experience with either the parent company or dealerships. In fact the exact opposite. Bend over backwards to be helpful and service oriented. I was savvy enough though to not pay the insane prices for servicing but used AAA quality independents for my services and parts.

My new Benz is simply another glorious progression in a long line of superb automobiles.

[HauptmannUK]

Our family business in the UK specialises in repair and servicing of MB and BMW (although we do work on other brands too...) so I have some knowledge of your problem.

 

First of all, if you are keeping this car then DO NOT use a sealer additive. A/C sealant reacts with water molecules at the site of a pinhole leak to form a 'plug'. They do not work effectively with O ring leaks or shaft seal leaks.  More importantly they will react with any moisture in your system and block the expansion valve. And worse still, if you have gas extracted in the future the additive may damage the recovery machine!!

 

First of all add some dye to the system and after a few days look for traces at the outlet of the evaporator condensate drain tube under the car. This will confirm a leak in the HVAC box (evap or evap connections).

 

Getting to the evaporator is a big job and books at around 10-12 hours, depending on variant.  Basically MB's mission is to make things overly complex and the W204 is no different..  Give me a Toyota or Honda any day of the week - the Japanese know how to build A/C !

 

MB evaporators suffer from pinholes due to the fact that the supplier (Behr) use dissimilar metals in their construction - which is a pretty stupid thing to do. Later production will have an anti-corrosion coating - don't know if yours will.  The W204s also suffered with mold growth on the evaps and were fitted with an auto-drying system, which I'll describe below.

 

When the dash is apart replace the evaporator (Behr are OE, VEMO are also good - do not fit a Chinese copy), replace O rings, expansion valve and receiver. I also suggest replacing heater matrix whilst you are in there.

 

Ensure the drain tubes are clear (there are two on most variants).

 

To combat corrosion and mould growth MB fitted an auto-drying feature which works as follows...

After driving with the A/C on full AUTO for the entire trip and parking the car with doors closed then after about one hour the A/C controller will activate the blower on slow speed for 15-30 minutes to dry the evaporator.  If during driving you switch the A/C out of AUTO, even for a moment, then this feature is deactivated so always leave the system in full auto for the entire trip.

 

If you can get the job done for ฿20k then that's an incredible bargain!

 

Edited November 9, 2022 by HauptmannUK

[itsari]

3 minutes ago, HauptmannUK said:

Our family business in the UK specialises in repair and servicing of MB and BMW (although we do work on other brands too...) so I have some knowledge of your problem.

 

First of all, if you are keeping this car then DO NOT use a sealer additive. A/C sealant reacts with water molecules at the site of a pinhole leak to form a 'plug'. They do not work effectively with O ring leaks or shaft seal leaks.  More importantly they will react with any moisture in your system and block the expansion valve. And worse still, if you have gas extracted in the future the additive may damage the recovery machine!!

 

First of all add some dye to the system and after a few days look for traces at the outlet of the evaporator condensate drain tube under the car. This will confirm a leak in the HVAC box (evap or evap connections).

 

Getting to the evaporator is a big job and books at around 10-12 hours, depending on variant.  Basically MB's mission is to make things overly complex and the W204 is no different..

 

MB evaporators suffer from pinholes due to the fact that the supplier (Behr) use dissimilar metals in their construction - which is a pretty stupid thing to do. Later production will have an anti-corrosion coating - don't know if yours will.  The W204s also suffered with mold growth on the evaps and were fitted with an auto-drying system, which I'll describe below.

 

When the dash is apart replace the evaporator (Behr are OE, VEMO are also good - do not fit a Chinese copy), replace O rings, expansion valve and receiver. I also suggest replacing heater matrix whilst you are in there.

 

Ensure the drain tubes are clear (there are two on most variants).

 

To combat corrosion and mould growth MB fitted an auto-drying feature which works as follows...

After driving with the A/C on full AUTO for the entire trip and parking the car with doors closed then after about one hour the A/C controller will activate the blower on slow speed for 15-30 minutes to dry the evaporator.  If during driving you switch the A/C out of AUTO, even for a moment, then this feature is deactivated so always leave the system in full auto for the entire trip.

 

Some knowledge is an understatement .

[Lacessit]

3 hours ago, Tropposurfer said:

Sorry you had a bu.mer of an experience with MB Lacessit. There are lemons (even in Benz's) and bad faith dealers for sure.

I've owned them for decades (in OZ, USA, Europe and now LOS) and never had a bad car, nor a bad experience with either the parent company or dealerships. In fact the exact opposite. Bend over backwards to be helpful and service oriented. I was savvy enough though to not pay the insane prices for servicing but used AAA quality independents for my services and parts.

My new Benz is simply another glorious progression in a long line of superb automobiles.

Fair enough. Having driven both, I have to say in German cars, BMW would be my preference.

Have you ever been in a Kia Stinger? Comparing that with the Merc counterpart 200 SLK, it has about 35% more boost on the turbo, and is $20,000 cheaper in Australia. It is a seriously good vehicle.

[Mansell]

If you have the bucks to own a Mercedes’ 20,000 baht is chicken feed…..just pay it. My wife’s insurance on her Suzuki yesterday was 23,000 baht.

in the States anything on a regular car that costs a hundred bucks will be on a Mercedes’ a thousand dollars most of the time. Pay and look happy.

[HauptmannUK]

25 minutes ago, Mansell said:

If you have the bucks to own a Mercedes’ 20,000 baht is chicken feed…..just pay it. My wife’s insurance on her Suzuki yesterday was 23,000 baht.

in the States anything on a regular car that costs a hundred bucks will be on a Mercedes’ a thousand dollars most of the time. Pay and look happy.

You're confusing THB and USD....

[ezzra]

Thank to one and all for a very useful information, the 20K repair estimate is from an non MB garage who specialise in repairing MB's for many years now, but i hate to see my very clean and tidy car gutted out. a real MB outlet will probably ask twice the amount, i will however make sure that who ever fixes it will do a proprer investigation before starting to dismantle the car...

[DaRoadrunner]

Leaks are found using ultra violet light which shows up the gas as a green colour where the leak is.

 

This is one time where I would not use the genuine Benz part. Copy parts will do and cost less.

[itsari]

8 hours ago, ezzra said:

Thank to one and all for a very useful information, the 20K repair estimate is from an non MB garage who specialise in repairing MB's for many years now, but i hate to see my very clean and tidy car gutted out. a real MB outlet will probably ask twice the amount, i will however make sure that who ever fixes it will do a proprer investigation before starting to dismantle the car...

Buy a Toyota or Honda in the future.

Forget German technology 

[HauptmannUK]

7 hours ago, DaRoadrunner said:

Leaks are found using ultra violet light which shows up the gas as a green colour where the leak is.

 

This is one time where I would not use the genuine Benz part. Copy parts will do and cost less.

A/C gas doesn't show up under UV - an oil-based UV fluorescent dye must be added into the system, e.g. Spectroline.   If the leak is from the evaporator then the dye will show up in the condensate.

 

Where a job involves a huge amount of labour it is unwise to attempt to save money by fitting 'copy parts'.  'Genuine Mercedes' evaporators are supplied by Behr and not overly expensive on the UK/EU aftermarket.  Not sure what's available in Thailand - might need to buy from the dealer. Don't fit a secondhand or 'unbranded' item unless you want to repeat the job.

Edited November 9, 2022 by HauptmannUK

[seedy]

6 hours ago, HauptmannUK said:

A/C gas doesn't show up under UV - an oil-based UV fluorescent dye must be added into the system, e.g. Spectroline.   If the leak is from the evaporator then the dye will show up in the condensate.

 

Where a job involves a huge amount of labour it is unwise to attempt to save money by fitting 'copy parts'.  'Genuine Mercedes' evaporators are supplied by Behr and not overly expensive on the UK/EU aftermarket.  Not sure what's available in Thailand - might need to buy from the dealer. Don't fit a secondhand or 'unbranded' item unless you want to repeat the job.

Excellent advice

You Tube has a channel - Car Ninja - German Auto Centre.

Compares a Chinese $100 water pump with a $600 - 700 German made one for a BMW.

These pumps have a circuit board inside, and guess which one failed in less than a year ? With no warranty.

Take a guess at what the R and R costs and you will NOT buy knockoffs in that application again.

https://www.youtube.com/channel/UCtEVJt0r0akdubSmLZhqf7A

[DJ54]

OP good luck …. Found this on YouTube don’t know if helpful or .. Cheers

 

https://www.youtube.com/watch?v=r6WNazHU988