GERALD´S CADILLACS


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DRY ICE CLEANING THE ENGINE AND ENGINE BAY OF MY 1974 COUPE DEVILLE. (VIDEO).

During my ongoing engine compartment clean up project, it was time to remove all the dirt, grime and oils which can be found inside an engine bay after 45 years - even in a low mileage car.
A conventional engine cleaning with a strong degreaser, steam or a pressure washer was not successful when I tried, because the main issue I had was overspray, which you cant remove with traditional cleaning methods.

During the undercarriage project last winter - the paint shop did not cover the engine bay good enough, and a lot of overspray settled down on the entire engine bay. It looked terrible!
This overspray is extremely difficult to remove, and this is why I thought of dry ice cleaning for the remains which I could not remove with clay and polishing.

I had some very good results with dry ice blasting during my undercarriage project for removing the undercoating.

Dry ice-blasting is a form of carbon dioxide cleaning, where dry ice, the solid form of carbon dioxide, is accelerated in a pressurized air stream and directed at a surface in order to clean it. An alternative media for non-abrasive blasting is water-ice, known as ice blasting.
The method is similar to other forms of abrasive blasting such as sand blasting, plastic bead blasting, or soda blasting but substitutes dry ice as the blasting medium. Dry-ice blasting leaves no chemical residue as dry ice sublimates at room temperature.
Dry-ice blasting involves propelling pellets at extremely high speeds. The actual dry-ice pellets are quite soft, and much less dense than other media used in blast-cleaning (i.e., sand or plastic pellets). Upon impact, the pellet sublimates almost immediately, transferring minimal kinetic energy to the surface on impact and producing minimal abrasion. The sublimation process absorbs a large volume of heat from the surface, producing shear stresses due to thermal shock. This is assumed to improve cleaning as the top layer of dirt or contaminant is expected to transfer more heat than the underlying substrate and flake off more easily. The efficiency and effectiveness of this process depends on the thermal conductivity of the substrate and contaminant. The rapid change in state from solid to gas also causes microscopic shock waves, which are also thought to assist in removing the contaminant.

Unlike abrasive media blasting you cannot remove rust with dry ice blasting.

With this cleaning process I could remove 99,99% of the overspray and the engine is now extremely clean. I will have to remove all of the remaining surface rust with rust remover, and then re-paint the areas which will then be bare metal. Some of the original paint had flaked off over the last 45 years, but I´m trying to keep as much in original paint as possible and only repaint where it is absolutely necessary. Areas of the block will get some fresh Bill Hirsch engine enamel and I had to repaint some brackets, pulleys and the power steering pump.

Below I have put together a short video to show how dry ice cleaning was done in my engine bay. Enjoy and make sure to watch in HD to be able to view all the details!


Here is a short video I shot during dry ice cleaning - it shows the process and explains it a little.
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You need a very strong compressor for dry ice cleaning - even a very good shop compressor is not strong enough and cant supply the necessary capacity of air.edge
Christoph with his dry ice blasting machine.edge
Loose paint will come off easily
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You can also clean weatherstripping and rubber hoses very well.edge
After cleaning - the overspray is gone :-)edge
After cleaning - the overspray is gone :-) All the hoses and wires are clean again.edge
After cleaning - the overspray is gone :-) All the hoses and wires are clean again.edge
You can also clean the carburetor with dry ice.edge
This is the area underneath the radiator. The surface rust will come off pretty easily with rust removing gel. Afterwards I will re- paint it.edge
As you can see its clean, but there is some surface rust remaining which I will have to remove before applying some fresh paint.edge
As you can see its clean, but there is some surface rust remaining which I will have to remove before applying some fresh paint. I will remove the fuel pump for painting.edge
As you can see its clean, but there is some surface rust remaining which I will have to remove before applying some fresh paint.

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SANDBLASTING AND DRY ICE BLASTING/CLEANING THE UNDERCARRIAGE OF THE 74 CADILLAC

The work on the undercarriage continues now after the problems I had last fall. As the new paint did not stick to the undercarriage at all, I have to redo the entire project I started in the fall of 2015 once again. The car already looked fantastic when I found out that I have a problem.
The paint shop wanted to have the undercarriage media blasted this time, to make sure that everything is 100% clean, and that the paint can stick to the metal much better due to a rough surface.

Personally I´m not a big fan of media blasting a non disassembled car, as so many things could go wrong and I do not recommend to do it to anybody else.
The paint shop really wanted to go this route though, and they said that they have a very experienced media blaster to perform the work.
They did tape the car for hours to make sure that the blasting media would not go close to any mechanical or fragile parts.
The blaster worked with very low pressure (1bar - 14psi) to get the old paint off and it really came off within minutes. He did not want to risk anything and so there were some areas with the old paint left after he was finished.

We then spent a whole day trying to get rid of the rest of the remaining paint, by hand. With 240 grit paper we worked on all the areas we could reach. After a whole day under the car it was clear that we could not reach all the areas and that the job would not be good enough.

I then contacted a dry ice blaster who took over to remove the rest of the remaining paint. Normally you cannot remove paint with dry ice blasting, but as the paint on my car´s undercarriage does not stick, it works. It took him a couple of hours to get everything off.
The undercarriage is now completely clean and back to bare metal once again. He even was able to remove some of the old undercoating in the rear wheel wells which the other dry ice blaster could not get off.

We will now degrease everything multiple times and then scuff all the metal. Then its time to mask all the necessary parts and repaint everything once again with 2k paint. I will keep you updated here on my website about the progress.

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The media blaster at work
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Media blasting the undercarriage.
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The bare metal wheel housing after blasting. The rest of the paint was removed later by hand and by dry ice cleaning.
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After blasting
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Ready for dry ice cleaning.
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The dry ice cleaner managed to get the last undercoating out of the rear wheel housings.
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Dry ice cleaning
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Everything is perfectly clean now.
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All the suspension parts were perfectly cleaned as well.

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DRY ICE BLASTING THE UNDERCARRIAGE OF THE 1974 CADILLAC

I´m restoring the undercarriage of my 1974 Cadillac Coupe DeVille. See below.
As I want to do it as perfectly as possible, I wanted to remove all the undercoating which was applied when the car was new.
I do not like rubberized undercoating, as you cannot see whats going on underneath. It can trap moisture and once it flakes off due to corrosion, there is already some major damage in the metal underneath.

There are different methods for removing the undercoating and most of the methods are a pain in the a**.
This stuff can be removed with a scraper and chemicals, or with heat and a scraper. Both methods will damage the metal underneath and scratch the paint on the underbody, and it takes forever…

As I did not want to use any of the methods mentioned above, I decided that I wanted to try dry ice blasting.

Dry ice-blasting is a form of carbon dioxide cleaning, where dry ice, the solid form of carbon dioxide, is accelerated in a pressurized air stream and directed at a surface in order to clean it. An alternative media for non-abrasive blasting is water-ice, known as ice blasting.
The method is similar to other forms of abrasive blasting such as sand blasting, plastic bead blasting, or soda blasting but substitutes dry ice as the blasting medium. Dry-ice blasting leaves no chemical residue as dry ice sublimates at room temperature.
Dry-ice blasting involves propelling pellets at extremely high speeds. The actual dry-ice pellets are quite soft, and much less dense than other media used in blast-cleaning (i.e. sand or plastic pellets). Upon impact, the pellet sublimates almost immediately, transferring minimal kinetic energy to the surface on impact and producing minimal abrasion. The sublimation process absorbs a large volume of heat from the surface, producing shear stresses due to thermal shock. This is assumed to improve cleaning as the top layer of dirt or contaminant is expected to transfer more heat than the underlying substrate and flake off more easily. The efficiency and effectiveness of this process depends on the thermal conductivity of the substrate and contaminant. The rapid change in state from solid to gas also causes microscopic shock waves, which are also thought to assist in removing the contaminant.

Unlike abrasive media blasting you cannot remove rust with dry ice blasting.

I found a company through the website of a classic car club, which is only a little over an hour away. I wanted to have it done before the first snow and as soon as possible, so that I could continue working on my car during the winter. The owner of the company did a great job. He is a very friendly and competent gentleman and it was a pleasure working with him.
Here is a short video how it was done: (make sure to watch in HD for proper image quality)

You can find all the pictures I took today in my restoration album.

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The car was lifted with a forklift and then covered in plastic.

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One of the rear wheel-housings before blasting - you can see the undercoating everywhere. edge
The same wheel housing after blasting - all the original paint was still very well preserved under the undercoating. As you can see originally the wheel housing was brown. During painting a lot of overspray from the body landed in the wheel housing. Then Cadillac added rubberized undercoating to protect the metal from stone chips and to keep the car more quiet. Luckily there is no rust to be found anywhere.
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During blasting.
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The original brown paint showed up underneath the undercoating. The paint is still in perfect condition.

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The original paint showed up underneath the undercoating in the wheel housings as well.
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After cleaning - it came out really nice! I will touch up some areas and conserve the others with a special transparent coating.
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I´m very happy with the result of the cleaning and will now have to protect everything and paint some areas.

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