I have a 71 Coupe that I am planning on having painted in the next few weeks.
There is an area in the paint on the hood right above the AC compressor that has small bubbles in it. The same pattern is also on the under side of the hood, so I am assuming that it is from the AC compressor slinging oil on the hood and making its way through the fibreglass.
I have searched for this topic on the forum and it seems like the only answer for the long term is to replace the hood.

Some posts have mentioned a sealer that can be put on the hood before painting,or a cleaner to help pull the oil out of the glass, but there is nothing mentioned about what sealer or cleaner in particular to use.

I really dont want to replace the hood as the car is a 40,000 original survivor.

Is there a way to remove, or seal this spot before painting?

 

I had the exact same problem on my 79 hood.

Before getting the car painted, I did the following:

1) fixed the leaky AC compressor so it doesn't happen again.
2) entire hood top (indeed whole car exterior as was repainting car) was taken down to the fiberglass using sandpaper, razor blade method,sanding board and DA orbal sander.
3) Removed hood,placed on my lawn in summer (heat lamp in garage in winter might also help), underside up (with old pad and plastic underneath). Used a putty knife to remove all the junk, cleaned with solution*, used putty knife / razor blade to get down to glass, put cloth soaked with solution on spot/area, covered with plastic(weights around edges sealing somewhat), let sit in sun most of the day wiping off and adding more solution a few times. I angled the hood inside towards the sun with props underneat - also served to allow air underneath.
4) when hood reinstalled,also did the rag w/solution, covered in plastic, soaked it that way for a few days (in garage in summer).

Car was repainted over a year ago, no signs of reappearance yet (crossed fingers).

The *solution I used - if I remember correct was the PPG cleaner for fiberglass (remove wax before sanding exterior). Might not hurt to also use household dish soap for initial cleanings as they also remove oils/waxs. The cleaner solution w/rag helps get into the pores of the glass. Found the solution/rag/plastic in sun trick when I was searching on the web myself back then (~ 2yrs ago).

I discussed this with the guy (great guy -now a friend) that painted my car - so he knew about it (I did 99% of prep work, sanding,removing windows, bumpers, door handles, etc.). They repainted my hood underside with the correct flat/mat black paint. I am not sure if they used any special sealers - I doubt it. I think the best bet is trying to do a good job of getting the oils out of the glass....time will tell how well this method works....

Good luck

 

My 71 is doing this also....After about 4 different AC compressors, all of which start to sling oil, I am going to a Vintage Air kit with a Sanden compressor. I will be switching to an L88 hood BUT I will have my stock SB hood repainted also...I am hoping the painter can get in there and "kill" the oil. My guess is he will have to go in there deep then re-gel coat it or something. There has to be a way...

I know my dad had a 67 coupe that got brake fluid on the top of the left fender by the MC....He had that thing painted like 3 times and the bubbles kept coming out after a few months...

 

I also fashioned a shield from aluminum that I bolted over the top of my R4 compressor so when (not if) it leaks again - it might help reduce how much gets on the hood. Here is the only pic I could find of the 'AC spatter shield' - note how the ends are bent downward on both sides.

 

BTW Ecklers sells a shield that can be bolted on the A6 compressor to catch the oil sling.

 

What?? You don't want your car to look factory original? That's how lots of them (with A/C) looked until they put the "blanket" under the hood in '73 or '74. {Mine looks the same.}

 

Hi Corvettetodd,

It appears from your descritpion you have oil saturated into your fiber glass hood.

This can be a problem for any refinishing process. Glad to see comments on how to stop the loss before attempting a repair.

The fiberglass has had absorbed the oil and now it has permeatted to the topside, hence bubbles in the paint.

The solution has been touched on by 'martinsw'. Treat the underside first. The oil needs to be removed from the affected area. The whole underside should be initially cleaned up to stop any further contamination to the underside of the hood. Once cleaned to your satisfaction apply quality wax and grease remover.

As a side note we personally used Anti Static degreaser from Sikkens, Akzo Nobel. The benefits of this anti static was to prevent any flash fires from applying and wiping the solvent. For those of you out there who are 'washing' down any fiberglass panels with solvents beware of static electricity that will set off a blaze to remember.

Once we had applied the degreaser by a spray bottle we 'floated' off the oils and then started with the top side. This consisted of initial wash and then as suggested cut open the 'bubbles' by sliding a single edged razor blade underneath to remove the bubble. After floating off the oil, we feathered back with a reasonable grit and washed in between with wax and degreaser on regular intervals.

With out continuous application of the degreaser we would physically 'grind' the oil back into the hood which would only lead to failure. After sanding to satisfaction an epoxy primer was applied and then high build polyester primer to level.

Fiberglass as we know is very porous and susceptible to absorbtion. Clear understanding off what needs to be done will lead to a successful repair.

Dano,