Advice on rusty exhaust hanger

[Oro_O]

I picked up a very clean, relatively low mile Volvo XC70 (2004) for my recent relapse of my life-long skiing addiction.

Going under it, it was very clean with all bushings, etc. in good shape, no issues to be found. It's a PNW car so not surprising. I did find the exhaust hanger on the muffler rusting badly. I was thinking to scrape/brush it as best I could, then use some Permatex Rust converter on it. After that, exhaust or grill paint? Ideas? The exhaust is all otherwise excellent so I need to arrest this asap to avoid a bigger hassle later.

The lug bolts were also rusty. I vinegar soaked them and then took away most of it with emery cloth. Then I gave two coats each of rust converter, Zinc coating (cold galvanizing spray), then a top coat of aluminum paint. They look good now but I know this won't work on exhaust as the zinc and paint layers won't take that heat.

 

[Racecarfan2]

Wire brush and converter is a sound plan.

 

[Trav]

I picked up a very clean, relatively low mile Volvo XC70 (2004) for my recent relapse of my life-long skiing addiction.

Going under it, it was very clean with all bushings, etc. in good shape, no issues to be found. It's a PNW car so not surprising. I did find the exhaust hanger on the muffler rusting badly. I was thinking to scrape/brush it as best I could, then use some Permatex Rust converter on it. After that, exhaust or grill paint? Ideas? The exhaust is all otherwise excellent so I need to arrest this asap to avoid a bigger hassle later.

The lug bolts were also rusty. I vinegar soaked them and then took away most of it with emery cloth. Then I gave two coats each of rust converter, Zinc coating (cold galvanizing spray), then a top coat of aluminum paint. They look good now but I know this won't work on exhaust as the zinc and paint layers won't take that heat.

There is not much life left in that hanger no matter what you do to it. I would shape one out of SS rod, cut the old one off and weld the new piece on.
It looks otherwise okay and should weld up without any trouble. McMaster-Carr has SS rod for about $15 a ft, if you cant do it have someone weld it for you.

 

[ABN_CBT_ENGR]

beat me to the draw on that one

 

[Redright9]

Have you checked what an exhaust show would cost to weld a new rod on? Probably not too much.. I bet more than a DIY project, but may be cheap enough to not have to spend your time doing it..

 

[Oro_O]

I was worried replacing the rod would be involved. I do pretty much everything but mount tires and weld.

I think I am going to get away ok. I was doing nothing hugely constructive this afternoon besides waiting on the last batch of lug bolts to dry/cure, and marinating a London Broil. I put on side on a ramp and went under to start cleaning it up. It's got more steel there and 75% of the weld in place. This pic may show better. I brushed a while longer and soaped/degreased it; when it's dry I'll apply converter, let that cure and paint.

I un-hung it and actually nothing bad happens. There's two stout hangers either side of the back pipe and they hold the muffler in place well even w/o that. I'll do this one, the un-hang those and treat them. They are a little nasty but not as bad.

 

[Trav]

I was worried replacing the rod would be involved. I do pretty much everything but mount tires and weld.

I think I am going to get away ok. I was doing nothing hugely constructive this afternoon besides waiting on the last batch of lug bolts to dry/cure, and marinating a London Broil. I put on side on a ramp and went under to start cleaning it up. It's got more steel there and 75% of the weld in place. This pic may show better. I brushed a while longer and soaped/degreased it; when it's dry I'll apply converter, let that cure and paint.

I un-hung it and actually nothing bad happens. There's two stout hangers either side of the back pipe and they hold the muffler in place well even w/o that. I'll do this one, the un-hang those and treat them. They are a little nasty but not as bad.

View attachment 27057

How much is left just off the pipe? The picture may be deceiving but I would guess that is where it will break when it does.

 

[eljefino]

If you aren't eager to weld that exhaust you might be able to get some allthread, a clamp and a coupling to extend one of the "legs". Cut the allthread to fit, orient the clamp juuuust right, and jam the all thread through the hanger where the old part used to live.

 

[Oro_O]

How much is left just off the pipe? The picture may be deceiving but I would guess that is where it will break when it does.

That's a very good point you make, as per usual. It's got wastage more than the rest of the rod, but about the same as the welded bit. I scraped in there particularly vigorously, and I have liquid converter, not spray, so I can get it all covered.

I would MUCH rather go through the hassle of cutting off the old, bending new rod and getting it welded than have it fail. I *think* I'm ok but I'm going to check it after we have had a fair amount of rain. if it's good then I'll check again in the spring. It will snow and salted roads regularly this winter though we don't live in it. Also, after a bad salted-road run, I have a hose near the parking spot and I spray my underside a bit. I did that when I lived in New England it kept my cars rust-free despite a lot of hard winter use.

 

[Oro_O]

OK, it's not the finest painting/refinishing I've ever done, but it should work. I'll check it later and make sure it's holding up. Tomorrow I'll unhang the back pipe rods and treat them.

 

[doitmyself]

Keep us posted. Nothing ventured, nothing gained. You can always go to plan B (welding) when you choose. Although, the materials cost to attempt rust abatement might surpass the weld repair.

Those milky type rust converters have an acrylic latex resin base that leaves a paint-like film after the conversion is completed. I'm curious if it will withstand the heat. I might be more tempted to use one of the non film forming liquid phosphoric acid type converters (OSPHO, etc.) and then just cover the rod in oil or grease. Silicone grease is good to about 400degrees F. Or maybe drench it in high heat paint. It's an experiment for sure.

Thanks for sharing.

 

[Oro_O]

Those milky type rust converters have an acrylic latex resin base that leaves a paint-like film after the conversion is completed. I'm curious if it will withstand the heat.

Smart comment.

I wasn't aware of that, but I realized it yesterday when I went to paint it over after the converter had cure time. I did the repair on a gravelled area to avoid messing up a paved surface. A spot where I spilled a small amount of the liquid converter (permatex from NAPA) had formed a "plate" of gravel - one chunk of gravel made up of 8 or 10 smallish pieces, bound up in a clear resin. It looked remarkably like peanut brittle. I realized right away that might not be as heat resistant as I thought, as I could tell it had some binding agent/resin/polymer in it I had not known about. There were no heat warnings on the label.

In the past I have used phosphoric acid, etc. for etching before finishing items. I think I'll wait to do other hangers in order to do a few drive cycles to see if I see signs of the converter not holding up beneath the paint. If so, I'll just use acid on the cleaned-up steel, and then trust the paint and check periodically.