I have a M model. I’ve owned it for 19 years. I’m also the A&P. I’m not an IA, just an A&P. I like using an IA for a second set of eyes. I’ve been through a lot with this airplane and feel that I know it pretty well. I’ve dealt with every issue that everyone has mentioned so far. Recently we updated the avionics with a 650xi, G5’s, and a GI275 MFD. The ”M” is possibly the best 172 every made. Maybe not for fitting avionics, the N is better for that
If it’s been in a hanger you could really have yourself a sweetheart there. Not a dealbreaker if it hasn’t, just more issues to workout.
Here’s a few questions for you, along with some items to consider.
-Damage history? Check the log books carefully.
-Hangered or not? Sun and corrosion does more damage than anything in my opinion. I’m in a hanger now but mine has been outside (covered) a lot over the years. I’ve worked my ass off staying on top of this and my plane is unbelievably clean because of this hard work. Someone mentioned that corrosion might be a dealbreaker. I wouldn’t go that far. It’s got corrosion. You can bet your ass is has some corrosion! Even if it has been treated with corrosion x or whatever. That stuff is great but it can’t get everywhere. We’ve treated inside the wings, tail, everything. I still find corrosion occasionally. I’ve always been able to take care of it and spot treat as needed. Recently found corrosion on the underneath side of the glareshield and under on the inside of the firewall. It all cleaned up and was painted during avionics installation.
What state you getting it from? Or where has it spent most of it’s life? Hopefully a dry climate.
Engine. Do you know which one. I’m guessing its an 0320-ETD. If so, it’s one of the best ever. The H model had some issues, not a big deal but it got a bad reputation which hurt it’s value. Someone mentioned exhaust/intake leaks. Of course this should be looked at but it’s generally not a big deal. I just put new intake gaskets and hoses on mine this week. Parts were only maybe $40 bucks. Obviously my labor was free but it only took an hour or two.
Engine hours: You said it has 900hrs. That’s doesn’t really matter much. Recommended TBO is 2000 but even that is not a requirement for most. A lot of people think that hours are the main concern. It’s not. Time (years SMOH) is probably the biggest deal in my opinion.
How many years has it been SMOH? The lycoming letter states 2000 hrs or 12 years I think. Most people never consider the second part. Neither is regulatory in most situations but it’s definitely something to consider. This Lycoming letter saved me a ton of money when I went through my divorce. The appraisal got slashed due to considerable years SMOH
If it’s been 15-20 years SMOH I would be check next to see if a top overhaul has been completed. If so, did they go with new or serviceable cylinders? Big difference price, and quality based on my experience.
Mags are another expensive item. They have really gone up in price. I put a brand new set with harnesses on not long ago. Check to see when the magnetos were overhauled or replaced. This has gotten to be a big deal recently. There’s a new service bulletin that’s pretty important to comply with. Not required, but important.
Seat rails: Someone mentioned this. Yeah, it’s always been a problem but it’s really not that big of a problem for a private owner. I put a new set in but if yours pass inspection you’ll probably be good for a long time. Flight schools are always wearing them out because the seats get moved about a lot. Once it becomes your personal airplane you won’t be moving the seats around that much, and when you do you’ll be careful not to drag the pins, you’ll place them in the holes instead
Nose strut: Yes this is a bit issue in my opinion. It doesn’t matter if it has been rebuilt. It’s still a freaking issue. Actually, I would prefer it not to have been rebuilt. At least then I know it’s hasn’t been leaking down in the first place.
What is a strut rebuild anyway? Depends on who you ask. Most mechanics just put the majority of a seal kit in. Most pilots consider that a rebuild. I can assure you that most mechanics only replace the seals that they think are bad (the easy ones) and usually they are right. I’ve “rebuilt” mine this way 3 times over the years. It wasn’t until recently that I got determined and really took this thing down to the bone. Actually, I’m just finishing up a full rebuild on mine now. This includes the upper o’ring, and lower 2 o’rings, that nobody ever replaces. I asked a mechanic bud of mine if he’s ever replaced the lowes. He said absolutely not, because it’s a pain, and they hardly ever leak there anyway. Not only do I have a full rebuild now, I located some more corrosion that I would never have caught otherwise.
The one item that never gets looked at is the outer steering collar. I talked with an ex-engineer from Cessna last week. He said it’s probably the most overlooked item on the nose gear. I believe it! It’s a total PIA to get it apart because of the huge snap ring. Mine was full of rust. About a hundred needle bearing in there. It has a grease fitting, but Cessna didn’t put internal groves to carry the grease in a number of the 172s. Even if it has internal tracks, all it takes is for it to become clogged and the rust forms. Thankfully, I was able to clean them up ok with gas. Then I let them soak in oil. Finally got them repacked properly with grease. So nice now!
Have it check for shimmy or play in the nose gear. People say that Cessnas are supposed to shake. That’s a bunch of BS. Get it right up front. If it’s shaking, you have work to do or it will get worse. I’m kinda anal about the nose gear being right
I wish I'd taken a better picture to show how terrible the condition of the rollers were.
Much more betta!
. Despite the FAA instructions which are confusing, every hole must be spot-faced (McFarlane has the bit) regardless of the actual screw/nut combo used. 
Also, the Cessna seat rail stop bars do not fit out of the box, even if you buy new ones. Before you install the rails, be sure to file the proper locations in the rails to allow them to fit. I called McFarlane and talked to Support. I was told this is the correct method, do not attempt to grind the stop bars to fit, there's not enough material.
