Hi All,
I recently purchased a 1992 RH drive RX-7. The car is in great condition, but I want to spruce up the engine bay. I'm dealing with what seems to be years of hard water buildup in a section where water may have pooled and dried repeatedly. I've tried using CLR, vinegar, soap, and a lot of elbow grease, but there's still a stubborn layer on top of the paint . It is for sure on top of the paint and not just loss of paint and seeing the bare metal. I've attached a photo to illustrate the issue. Has anyone successfully tackled this cleaning challenge?

 

When I got my car the engine bay was caked in grease and oil because the PO vented oil vapors directly into the bay. I had really good results with "Meguiar's super degreaser".

It looks like that might just be degraded paint in your third photo. I've seen stuff like that in a lot of fd engine bays that still have the original paint. Heck, mine looks like that too in some areas, but silver.

Hope that helps!

 

looks like remnants of cosmoline. this stuff works well: https://www.summitracing.com/parts/m...FunwuC8d4ZPswA

 

https://fb.watch/tI1vBxldef/

 

If you’re sure it’s ON the paint and nothing else works I’d remove the fender bolt and try some 2000 grit wet-sand paper and/or just compound…steering clear of those cloth patches.
I have fat fingers and in the tight corners I’ve used an eraser with compound or with a rag and compound.

 

before you try sandpaper, check to see if it is old cosmoline (anti corrosion coating).