View Full Version : Rust in cylinders...bad?

Josh Q
06-05-2004, 07:11 PM
So I went to take the intake out of the engine bay because I'm going to paint it before putting it back on the head. And I see surface rust in the cylinders. Is this bad? I have a pic of it but no place to host it if anyone wants to host it somewhere for me. Should I just oil it up with motor oil and get as much off as possible and let it take the rest off when I fire it up?

06-05-2004, 07:18 PM
Can you give us some info on the engine's history. How many miles, when it was last run, etc.

Josh Q
06-05-2004, 07:50 PM
It has 140k on it, has had the head off for 3 months. The hood has been on the car so no rain has gotten in there.

06-05-2004, 09:25 PM
It has 140k on it, has had the head off for 3 months. The hood has been on the car so no rain has gotten in there.

Was it very damp???

06-05-2004, 10:06 PM
If the head was off, you'll get some rust. Is it on the cylinder walls or just the pistons? Either way, if you're going to be rebuilding it, have it machined and balanced. Nothing worse than putting a lot of money into a new engine only to have it die on you because it wasn't rebuilt the right way.

Josh Q
06-05-2004, 11:34 PM
Now I'm not rebuilding it right now. It's kind of damp as I live in the Seattle area. It's on the cylinder walls. Most of it came off by wiping it with a rag and I think I can get the rest off with oil and a rag.

06-05-2004, 11:43 PM
Josh, at this point, I think it should be OK. After the engine goes back into use, I'd imagine what rust is left won't last very long.

Josh Q
06-05-2004, 11:47 PM
Yeah, like I said...after I wiped it off it started to really come of and only very little stayed on. I'll just take some 80 grit sandpaper to the walls and it should come off.

06-06-2004, 02:30 AM
sanding cylnder walls ? :?

06-06-2004, 03:18 AM
yeah, I dunno how that could be a good idea....

06-06-2004, 10:43 AM
If you got most of the rust of i wouldn't worry about it. If there a little still on the walls it will probably pretty much come off instanly once you start your car. If you were gonna sand it don't use an 80 grit paper thats way to harsh. Get a pretty fine grit like 400+, and just go easy not much pressure. But i think it should be fine if you wiped most of it off.

Josh Q
06-06-2004, 11:11 AM
yeah, I dunno how that could be a good idea....
:lol: :lol: :lol: Hahahaha...I got you guys! I was gonna see if anyone caught that. No, I know that doing anything to the cylinder walls is a bad thing, just wanted to see if anyone was paying attention. :D

06-06-2004, 12:42 PM
should we believe him?

06-06-2004, 01:03 PM
I dunno...when I saw that...my eyebrow went up...and I thought "That's not something I'd do, but if he thinks that's a good idea..."

Josh Q
06-06-2004, 05:02 PM
No I have heard of other people talking about doing that and I was like "NO! You don't even want to take anything to the walls that will scare/gouge it" But seriously, with 80 grit you could almost bore the cylinders out with that stuff!

Jay Stock E30
06-08-2004, 10:54 AM
first off....WOW

secondly the only thing I would take to my cyl walls would be a hone

thirdly rust on the cyl. walls would act like sand paper once they start going up and down, I'm sure thatd be awsome for the piston rings.

Josh does your block still have the factory hone marks? when I rebuilt my i engine in prep for the twin turbo project my block still had the factory hone marks at 230k miles. I thought that was pretty sweet.

06-08-2004, 11:30 AM
as long as you dont have rust on the cylnder walls it should be fine. bring each pistion to TDC and use a small fine wire brush to knock off as much of the rust on the tops of the pistions. spray with wd40 and wipd

if you have rust on the cylnder walls the only safe thing to do is take it to a machinest and have him bore the cylnder walls. it is very difficul;t to determine how far the rust goes into the cylnder wall, so simply scuffing with 80 grit wont do anything but make huge scratches in the cylnder wall. it needs to be bored, honed and cross hatched if you have ANY rust on the cylnder walls. otherwise ythe rings will not seat, or become unseated, can cause ringlands to brake,. can contanminate the oil with rust oxides and make premature wear on the barrings, and could make compression numbers eratic.

Josh Q
06-08-2004, 12:37 PM
I got all of the rust off the walls (it was very mild surface rust) by wiping it with a rag. I can still see the hone marks from the factory. And btw, I really wasn't serious about taking sandpaper to the walls. I'm nervous about working anywhere around the block with the head off in case I drop something and gouge the walls, let alone purposely taking sandpaper to it.