Best way to prep engine bay for paint

[lalojamesliz 56]

I'm just about done welding in the engine bay and now I need to clean it up so I can paint it. 

It has surface rust in a few tight areas especially around the master cylinder.   I've been using a wire wheel but the flying bristles is getting old. 

I seriously considered buying one of those dustless blasters but even for what looks like the one that looks like a 50 gallon air compressor is like $8k and you still need a air compressor on a trailer. Another 4k for a used one.  Yeah it would be very nice but then I would have to start blasting cars to get me money back.... I don't know anyone that builds cars besides you guys :(

[aslanefe 333]

I put a face shield, thick welding gloves and a thick coat to wire brush it, then put "Ospho".

[lalojamesliz 56]

The first time I used a wire wheel on my mustang after I took off the fenders I didn't know the bristles fly off. I just plowed thought but in the end I had multiple bristles in my legs and arms 

Later that night I found one in my inner bicep area.  Good times ha ha ha

 

[lalojamesliz 56]

1 hour ago, aslanefe said:

I put a face shield, thick welding gloves and a thick coat to wire brush it, then put "Ospho".

I never knew of Ospho. Thank you

I just ordered a gallon. 

[aslanefe 333]

52 minutes ago, lalojamesliz said:

I never knew of Ospho. Thank you

I just ordered a gallon. 

Ospho is cheaper at Ace hardware.

[lalojamesliz 56]

Ah crap. I'll try to cancel my order 

[lalojamesliz 56]

Ah crap. I'll try to cancel my order

Well for the paint I'll look for some high temp paint and for under the fenders I'm thinking of a raptor bed liner my son used on his truck. It's holding up great. Underneath I'll probably just clean the buildup then degrease a few times and pressure wash. I'm lucky the rust is minimal on my mustang.  

[Midlife 814]

Have you tried 3M Roloc discs?  They cut through rust easily and are useful for grinding down welds as well. 

https://www.amazon.com/Coceca-Inches-Surface-Conditioning-Sanding/dp/B07T1M9KC1/ref=sr_1_2?dchild=1&keywords=roloc+discs&qid=1624843103&sr=8-2

[lalojamesliz 56]

9 hours ago, Midlife said:

Have you tried 3M Roloc discs?  They cut through rust easily and are useful for grinding down welds as well. 

https://www.amazon.com/Coceca-Inches-Surface-Conditioning-Sanding/dp/B07T1M9KC1/ref=sr_1_2?dchild=1&keywords=roloc+discs&qid=1624843103&sr=8-2

I have some but the 3m brand. 

They are a little pricey and don't last long so I try to be careful on how I use them but these are much cheaper.  I'll try these for the tight areas.  

Thanks for the link!

[JayEstes 172]

Here is something you can try.  I found the near final prep phase that worked great for me was a small pan of lacquer thinner and a scotch bite pad and a cloth rag.  From the pics I see, you are close to or at the stage I would revert to the scotchbrite pad with lacquer thinner technique.  Once you have most of the big crud removed (I would say you are definitely there).  I would get a 1 qt disposable tupperware and fill it halfway with lacquer thinner.  I get the best and thickest pair of gloves I can find (PVC gloves are the only thing that ever provided much protection from the strong lacquer thinner).  Nitrile will melt instantly so don't use that, and other rubber gloves may work for awhile.  Even the PVC gets hard and crunchy after several uses, but for the most part it protected my hands.

Just dip the pad in lacquer thinner and gently rub the surface with it.  After you have scrubbed an area briefly, a lot of crud and grease and oil will be released.  dip the rag in the same stuff and wipe away the crud.  examine the surface and feel of it with a bare hand after the lacquer thinner has evaporated.  The goal is NOT to remove everything (it will do that if you keep rubbing!) but to leave the surface with 1 or 3 things: 1) a very clean and smooth original paint layer, 2) a very clean and smooth original primer layer, or 3) bare metal.  For myself the goal is to get to stage 1 or 2, but avoid 3 where you can.  As long as the metal is good and the primer and paint are original, and you have all the dirt and crud off - you are good to coat with the base layer of your new primer.  Where everything is stripped down to bare metal, just make sure the surface feels smooth with areas that have primer or primer & paint on them.

Once I have a whole section ready using the lacquer thinner + scotch brite pad followed by lacquer thinner + rag , I would rattle can engine primer over the surface I had just prepared.  Do it early because the laquer thinner softens the paint/primer and scratches the surfaces and you get a great bond with that new primer base.  And you want to do it before it can get dirty again or rust starts setting back in (this can happen literally overnight).

When I did my engine compartment, I followed this work by going back in and caulking up the metal seams with a hard/firm long-lasting caulk that would accept paint (be sure not to caulk lower edges so if water comes in from the other side it can drain back out).  When that dried, I put a full coat of primer over the top of that, and then the paint.  I got really exceptional results doing this and it was not a ton of work.

One caution is that this method will put a TON of black paint/oil/dirt sludge on the ground under where you are working.  Your shoes and pants will get coated, and if you don't put down a drop cloth or large cardboard, it will blacken your floor good.  Do the prepwork by covering the ground under you well before you do this work.   I wound up wearing tyvek overalls for this work.  It's messy but satisfying.

For RUST:  I have used Ospho a lot.  I have found another good solution - perhaps even better - but it works a little slower.  That is Evaporust.  The instructions call for you to soak a paper towel or something with it and soak it through, then lay the towel over the rusted metal.  I find that it needs to sit overnight, and if the rust is bad, the next day I brush and clean it as much as possible and do it again.  One benefit over ospho is that it doesn't leave behind the white powder when it dries.  One downside maybe expense.  However, a friend told be he got a gallon of it for $17 on amazon.  I use this mostly for nuts and bolts - the fluid can be reused many times if you are using it as a dipping fluid.

 

[JayEstes 172]

22 hours ago, lalojamesliz said:

Ah crap. I'll try to cancel my order

Well for the paint I'll look for some high temp paint and for under the fenders I'm thinking of a raptor bed liner my son used on his truck. It's holding up great. Underneath I'll probably just clean the buildup then degrease a few times and pressure wash. I'm lucky the rust is minimal on my mustang.  

Under the fenders, (after I cleaned them well with a wire brush on a 4in grinder wheel), I wiped it down with lacquer thinner to clean, and put a good coat of rattle can primer on.  Immediately thereafter I applied some rattle can truck bed liner - I am SUPER happy with the rattle can truck bed liner under the fenders... It's tough as a boot and cleans off really easily!  I'm 4-5 yrs hence now and I have zero complaints with that stuff! 

[Mach1 Driver 560]

13 hours ago, JayEstes said:

... and put a good coat of rattle can primer on.  Immediately thereafter I applied some rattle can truck bed liner 

Jay, what products did you use; engine primer, caulk, and bed liner? Doesn't bed liner have a rough texture?

[JayEstes 172]

I prefer Duplicor's engine paint primer.  

 

And I use Duplicolors' ford semi-gloss black engine paint everywhere too.   If you're careful with this sprayer, you can get a very nice finish with the semi-gloss black:

 

 

And for the truckbed liner, I use Rustoleum.  I find it is not anywhere near as rough as what you would see in a truckbed, in fact, the surface is not even very orange peely, but it is in some sense "rough" as compared to paint.  Good thing is, if you put it down on a good primer or primer or bare metal... it is not coming off, and it is hard a nails! 

I've had mine in the wheel wells for about 15Kmi now.  I just went and wiped the road dirt off with a damp towel, and this is what it looks like behind the drivers wheel:

Now, for caulk?  I am struggling to remember..  I wanted something that dried pretty hard and would accept paint.  I didn't want it too silicon-ized because even cured that stuff is very rubbery.  I found something at the HW store, but damn if I can recall what it was....  It needs to be something a little more flexible that JB weld, but significantly less than silicone (if JB weld is a 1, and 100% silicone is 10, you want to get something in the 3 to 4 range.  This is so the paint or bed liner wont chip off the caulked surface easily.  And you don't want it too hard because as the body panels move relative to one another (pot holes on teh road or whatever, it needs to give some).  and when you put it in and it's cured, I cover with primer paint or truckbed liner immediately, so it has a fresh surface to bond to.

Hope that helps.

Jay

[Mach1 Driver 560]

Thanks, that was very helpful.

[JayEstes 172]

I might add that you don't really need a primer under that truckbed liner..  It'll go right onto bare metal (as long as it is really clean and dry I always wipe with laquer thinner or IPA right before applying) and it sticks hard.  Great stuff - even if a little expensive - IMO.

 

[JayEstes 172]

And this has all made me realize, that given how much trouble I have had regarding brake system, and leaks onto the interior firewall etc, I would paint the entire area shown within the black highlight with the truckbed liner. 

My impression is that the bed liner is going to be more tolerant of having brake fluid dripped on it.  There's sometimes some dripped when I refill, and then I had my rear brake prop valve fail and leak fluid all down the side engine compartment wall.  I didn't notice at first, so a lot of the paint I had applies there either came off or softened.  Perhaps run a test of the liner.  Spray some of that truckbed liner on a surface and let it dry, then apply brake fluid to it, and see if it can withstand the brake fluid better than the paint.  This is not an area of the car that is easy to see and the black semi-gloss will be a close match in color.  It is an area that gets a fair bit of brake fluid on it, and having something that can take that will be better overall.

Do a good job while you have it in this state... you won't have a chance to work it like this maybe ever again - it's worth the time to get this stuff correct!

 

[lalojamesliz 56]

Got a bag full to try..... Tomorrow morning when it's not 104 degrees in my garage

Thanks Midlife

[RPM 1,190]

This is the type of wire drum I was talking about yesterday. 

[Mach1 Driver 560]

16 minutes ago, RPM said:

This is the type of wire drum I was talking about yesterday. 

?? Yeah I remember reading that somewhere, but I don't see your post in this thread. Have you been using your magical powers again?

[Midlife 814]

That wire brush is the one that sheds metal slivers like nobody's business.  Huh...that explains a lot about RPM!

[RPM 1,190]

12 hours ago, Mach1 Driver said:

?? Yeah I remember reading that somewhere, but I don't see your post in this thread. Have you been using your magical powers again?

Ha ha ha! No magic involved, I was talking to Lalojames in person, at his house. 

[RPM 1,190]

3 hours ago, Midlife said:

That wire brush is the one that sheds metal slivers like nobody's business.  Huh...that explains a lot about RPM!

They don't shed too bad when used on the pneumatic angled die grinder at not max speed. 

[Mach1 Driver 560]

On 6/30/2021 at 11:48 AM, JayEstes said:

And for the truckbed liner, I use Rustoleum.  I find it is not anywhere near as rough as what you would see in a truckbed, in fact, the surface is not even very orange peely, but it is in some sense "rough" as compared to paint.  Good thing is, if you put it down on a good primer or primer or bare metal... it is not coming off, and it is hard a nails! 

I see the Rust-Oleum even has a professional grade of this stuff that is a 2k epoxy, but it appears to be very textured.

[lalojamesliz 56]

On 7/1/2021 at 11:04 AM, RPM said:

This is the type of wire drum I was talking about yesterday. 

 

I thought you were talking about the twisted ones..... I might have one of these that I'll need to try out.  I tried out the pads Midlife sent me a link to and damn those things grind down everything fast.

Progress is slow right now since my days off are gone but I'll continue on my next days off. 

Yesterday I found out my suspension kit already shipped out and will be here in a few days so I need to work double time on this.  So much to do and so little time.  My goal is to start and drive it this year!!!!

[JayEstes 172]

16 hours ago, Mach1 Driver said:

I see the Rust-Oleum even has a professional grade of this stuff that is a 2k epoxy, but it appears to be very textured.

Thats interesting.  I really like the stuff I have without the texturing.  I'm amazed at how hard the stuff is.  even behind the wheels, rocks don't affect it much.  Minor nics there are 15kmi is good enough for me.