VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Honeycomb Expert Wanted......

Looking forward to your next post on the radiator cleaning exercise. You would think that having it boiled out by "professionals" would have gotten out what you have with chemical cleaners. The fumes from muratic acid are corrosive. Be careful how and where you store it. If kept in an enclosed garage the acid fumes can cause your tools and other metal components to rust. I don't even trust it being in a sealed container.

I'm with barry22 on the acid part. Trying to save an old radiator that will probably only be marginal at best, is not worth the effort or the risk you are taking with corrosive materials. Bite the bullet and get a new radiator and then you will have way more time for golf.....and your old car will be happy too.

:( :( :(

While true that Muriatic Acid (aka Concentrated Hydrochloric Acid) is hazardous it can and has saved many old radiators that were clogged with hard water deposits. Nearly every swimming pool or hot tub owner is familiar with it and can be used and stored safely. The critical information is on the label. Read it completely and adhere to the directions for use and it is safe to use. FYI, your stomach contains a fairly strong concentration of hydrochloric acid.

Update: As I stated before I gained a little time each flush. This time after flushing it out the 2nd time with Prestone radiator cleaner the water came out almost as dirty as the first time and I gained another 3 minutes or so. Each time I flushed it out and filled with clean water I felt the top of the radiator at 180 degrees and then the bottom and each time it felt a little cooler so I knew I was gaining. One thing about the Prestone radiator cleaner is that after it ran so long it would heat up faster because the water got so dirty it wasn't cooling through the radiator. I started the 3rd flushing with Prestone and will let you know how much I gain this time as the water once again is getting dirty. Hope to get up to 15 minutes before it hits 200 degrees.
Chipper, does the muratic acid work better when it's hot or doesn't it make any difference?

It needs to be hot to work best. Best to read the long version posted a while back just to be safe. But if you are comfortable handling hazardous chemicals, the short version of the process is to put in 2-3% solution (about qt. per cooling system that has been rinced with clean water). Run until really warm, shut off, let soak and cool, run again, repeat a few times for a total of 1/2 to 1 hour. Drain, flush with clean water several times. Neutralize with small box of baking soda mixed in water. Make sure to mix the muriatic acid into water slowly in bucket and then add to cooling system. May need to repeat until the drained acid is nearly colorless and not bubbling (or foam) is noted in the radiator when engine is off.

Update: Well, I ran the 3rd solution of Prestone Radiator Cleaner and it came out around 60% as dirty as the 1st. I then flushed twice and filled with water. I was going to let it run untill it hit 200 degrees but when it got to 198 degrees it then went down to 195 then back 199 and stayed there for 30 minutes so I shut it off. Then with the temperature around a nice comfortable 62 degrees out side I ran it for a 1/2 hour and it stayed at 185 degrees. The bottom of the radiator does feel much cooler than the top now. The last time I ran it, it was 80 degrees out and it got up to 199 degrees and stayed there. Now I have to decide if I should once again clean with muratic acid and another shot of Prestone Cleaner or go with just the Prestone cleaner. One question, when I drive it down the road once I get it ready will it get hotter than running in the shop or can I expect it to run cooler or about the same? Oh yes, when I just drained it, the water came out reddish with rust so I know there is still more in there.
Will have another experiment going in Electrical section.

One other thing may help on flushing. I back flushed a radiator by reversing the hoses and ran the car with 2 Gano filters in and out of the line of the radiator to catch the particles from the radiator and block. I was surprised how many particles came out of what I thought was a fairly clean radator. I drove this way a few times and then reinstalled the hoses the proper way. It has been OK for about 7 years. I had a little seepage in a spot and put in a teaspoon of pepper in the radiator which stopped this.
Naturally it would have been better to buy a new core but I don't drive long distances. I have bought new cores for 2 other cars from the filling Station but not installed them yet.

Jerry,
You will continue to get red rusty water until you passivate the metal. Best way is to add coolant with corrosion inhibitors. If there is any remaining acid then the inhibitors can be rapidly neutralized so flushing after cleaning is critical. Alternate is separate corrosion inhibitor. I do not recommend the 'soluable oils' that some use.

Thanks Doug & Chipper. I learn something new every day. I did stop by the Feed Store and they have the coolant with corrosion inhibitors so will get some.

I enjoyed all the comments on radiators and thought I'd throw in a couple of comments.
I put a NOS honeycomb core with my tanks fitted into my 28 and it works exactly how it was supposed to, and remember that it is a lot hotter here in Australia than most of US.
Another way if your car is a driver rather than a show car is to fit a modern core and very carefully saw off a 1/4" vertical section of your old honeycomb and use it as a grill. Because the new core is a lot thinner (and more efficient) than the original, the honeycomb veneer can be soldered to the tanks in it's original position. Looks original from the outside but performs better. A lot of the blokes out here have done this with great success and price is about $400 US (based on $600 AU)
I recently put a new core in my 34 Master and we did a trip where the temperature was well over 100 degrees in the sun and the old 34 ran under 190 all day, can't same the driver and passenger did though
Chris