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Painting a BJ8 Radiator - any advice?

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SteveHall64Healey

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Last year, I stripped the radiator of my BJ8 down to bare metal (brass tanks) and then painted it using Dupli-Color Engine enamel. Last week, a significant crack in the paint appeared, and then pieces (size of a quarter) came cleanly off, exposing the clean brass below. Clearly, the paint did not adequately adhere, despite my having taken great pains to strip and then thoroughly clean the surface before painting.

Had anyone had success painting their rad? What prep and products did you use?

I looked at Radiator Paint on the Eastwood site and asked about prep. They recommended a ā€˜misting of self-etching primer firstā€™, however the product spec for self-etching primer states that it is only stable to 170F....

thanks
Steve
 
Hi Steve,

Before I would have painted the tank, I would have applied a primer to get grater adherence to the cleaned metal. Also, CaptRandy had a good question, as if stripper sediment is not eliminated, it could cause those areas not to adhere to the metal. At this point, I would remove the present coating, wash the clean metal with water and allow to thoroughly dry, apply a primer and then apply the finishing coats.

Yes, a great deal of work but I expect it will last longer then your present application.

Just my thoughts,
Ray(64BJ8P1)
 
Hi, the entire top of the tank was stripped with a methylene chloride paint stripper, then cleaned with Varsol then acetone. I roughed the metal up with 1000 grit before a final wipe down with acetone followed by compressed air. Only half of the top tank has had paint loss.
 
I think a primer is a good idea, but I canā€™t seem to find one that tolerates higher temperatures. Iā€™d particularly like to use a primer that someone in this forum has used successfully rather than just find one on the Internet....
 
Hi-Temp header/exhaust manifold paint at Autozone, they have the primer too. I wouldn't do much sanding,
just an etch with Ospho or even Naval Jelly
 
I think the 1000 grit is too fine to promote good bonding.
 
dancrim said:
Hi-Temp header/exhaust manifold paint at Autozone, they have the primer too. I wouldn't do much sanding,
just an etch with Ospho or even Naval Jelly
Click to expand...


This is similar to what I have done for years.
, except ,do not etch or sand.

Additionally": send radiator to shop and have it stripped with instructions "DO NOT PAINT".

Then follow dancrims advice on paint type or as I use Hi Temp Engine paint


OH: immediately after spray painting the fan shroud red, have a brush handy to add the brush lines.
​
 
prep cleaned brass tank , sanding with 600 is better, use PPG DX 330 wax and grease remover,( Usually after I chemically strip tank I wash with warm water, scrub the crap out of it with scotch brite pads and tooth brush in crevises)
then after compressed air drying , tack down and I use PPG DP epoxy primer(black) thinned out as a sealer, ( its really thin ,you do not want too much material such as a sanding primer or etching primer, this stuff sticks to glass ! )
then I use PPG DCC 9300 ( black) with flattening agent to make it just under semi gloss , at this point you can also use your spray can of choice. The DP epoxy is what does the trick for adhesion. FOr the core part If radiator is out of car I would just use a spray can and keep it thin . The top is seen and regularly cleaned. If you do it right you cannot notice any color or sheen differences between the two and urethane will provide some protection paintwise to some abuse. Bottom of tank same way top is done. FWIW .
 
I painted the rad in the spring of 2018 and the finish was fine until 3 weeks ago when we hit a major cold snap. The car resides in my garage, which is attached to the house, but it was probably subjected to temperatures as low as -15F.
 
Just a thought...brass sheet metal expands /contracts with heating/cooling...just wondering if the engine paint you used is made to flex that much? There are paints (in spray cans) specifically for automotive radiators.
 
I think you could be right. That said, I think an appropriate primer is essential too, since the paint came off in fairly large shards, despite surface prep being meticulous.

My inclination would be to use the radiator paint from Eastwood but use an etching primer with a broad temperature stability range.
 
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Hi Steve,

In your first attempt, I think you did a job more appropriate for painting a fender. However, as you have indicated, the radiator does expand and contract so the paint needs something more to grab and your 1000 grit sanding made the surface to smooth to provide sufficient grip. I agree with Steveg as the radiator gets hot but within the limits of standard
Rustoleum or Krylon spray paints (I used a satin black Rustoleum last painted around 15 years ago). I roughed up the tanks with a medium grit paper for the primer to grab. The primer filled in any roughness and provided a good adhesive surface for the final paint to grip.

Considering the red fan guard originally had brush marks in the paint from the factory, I would suggest you not overdo the finish on the tank.

All the best,
Ray(64BJ8P1)
​
 
This system has work for many years on all my radiators, including my vintage racer

- Stripe & Scruff sand with 320 grit

- Solvent wipe with Xylol (acetone too fast)

- Apply one light even coat .5 dry mils. https://www.tcpglobal.com/SEM-39673_5.html?sc=115&category=3837722#.XGSm71VKjIU

- Apply two coat medium coats 2 dry mils. sanding between coats with 400 https://www.tcpglobal.com/SEM-42003_6.html?sc=115&category=3837720#.XGSoU1VKjIU

- Apply two medium finish coats 2 dry mils. no sanding between https://www.eastwood.com/2k-aero-spray-rat-rod-satin-black-47968.html
 
Update:

I removed the radiator and found the paint on the lower tank came off quite readily too. The parts of the rad made of steel held the paint quite well, while brass areas had little/no adhesion.

I took a piece of brass sheet metal and did the following:

1) sanded smooth with 325 grit sandpaper.
2) washed with warm soapy water. Dried thoroughly.
3) cleaned with Eastwood prep (contains xylenol as main ingredient). Allows 30 minutes to dry.
4) gave two coats of Eastwood self etching black primer, leaving 15 minutes between coats.
5) waited 4 hours, then gave two coats Eastwood radiator black paint in satin, waiting 30 minutes between coats. (note: primer and finish coat applied per instructions on label).
6) allowed to dry for 24 hours.
7) baked at 220F for one hour. Paint finish appears to be unaffected. Allowed to cool to room temperature.
8) placed piece outside at 20F for two hours, then allowed to return to room temperature. Paint finish unaffected.
9) attempted to scratch surface with my finger nail - paint did not come loose.
10) bent piece - again paint unaffected.

Looks like this process results in a temperature-stable finish, so will repeat the process on the radiator itself.

Note: the satin finish is quite nice but it is actually quite low gloss - too close to flat to look factory correct, so will use the Eastwood radiator paint gloss on the radiator.
 
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