The International Cessna^® 170 Association

Hello Everyone,

Started the annual today and early up was the compression test. last year - 90 hours ago all compressions were 74-78 range. This year #2 was at 51. Today the no-go limit was at 44, so we tested the cyl. obtained 51 on the gage and could hear lots of air bypassing the rings (ear to the oil fill tube).

Oil consumption is about 1 qt every 4-5 hours. Oil analysis is reading normal, and as a matter of fact gets slight improvements with each oil change. We did a bore scope inspection and did not see anything really bad - however two items to note.

1) more oil than normal in the lowest point of the cyl.
2) a defenative discoloration in the cyl wall about 3/4 the way up the barrel.

Cyl. has roughly 800 hours on it. According to the TCM service bul. we could have left the cyl. in place and rechecked after 100 hrs. I was not particularly comfortable with that and elected to pull the cyl. If after pulling the cyl. and all appeared fine, one possibility was to re-seal and run for a while longer and test again at say 25 or 50 hrs.

We pulled the cyl and discovered the top two rings to be frozen in the lands. So off it came and I sent it out to Aircraft Cyl. Repair in Whitmanville, MA for an overhaul. Inspection into the engine after the cyl was off revealed what looks like welding inside the case and then grinding with a die-grinder, but no mention of this in the logs. Also looking back to where the cam disapears into the accessory case their appears to have been more die grinding. Could it be that the overhaul shop was du-burring??

Since it's major overhaul in 91, only the #5 cyl. has been replaced (twice).

I'll keep you posted...

Kyle

Case repairs (welding/grinding) may be done under a CRS and no record will exist in the engine log other than perhaps mention of a "yellow tag" after inspection or case-ovhl. The "yellow tag" ...if found, likely would only refer to a Work Order, which no longer exists even.

Other ways a case can undergo such repairs without obvious notes in the records is if the engine was ever "remanufactured".

All that's not recorded....is not necessarily illegal. It may just be old news.

In any case (pardon the pun) if it's held together for so many years and hours, it's not likely a bad repair, whoever did it.

Well that makes sense. And the repairs seem to be holding up just fine. Turns out we had to take one more cylinder off - #5, and that was a new millenium cyl. installed in 2000. Only about 300 hrs + or - since. That cyl. was full of oil and had a section about 1 1/2" long of rust on the cyl. wall. Prior to our use of about 100 hrs per year for the last two years, the plane didn't get allot of use (about 10 to 20 hrs. per year) and that may explain the rust. None of the other cylinders have any rust - just #5.

While all of the exhoust and intake components are off the engine I took all the aluminum baffling parts to the parts cleaner and then sandblasted them for painting. Will re-install with new baffle seals.

Last night as I was looking at the remaining four cylinders - and their associated leaks I'm thinking, now is the time to re-seal the other 4 cylinders and stop the leaks as I'm hoping I won't have it stripped back this far for a long time to come... It does seem like all of you have had mixed results with seal kits.

Question - facing forward in the case are two threaded plugs, one each side just below the crank - what are they sealed with as both of mine are leaking?

The tail-pull handle kit came yesterday and I fabricated a plywood runway to lay down on as we work inside the empannage. It required two slits on the first section and one slit on the second for cables but should make working back there much easier.

Will update soon... Oh and I almost forgot, happy New Year to all

Kyle

According to Continentals SIL 99-2A on lubricants and sealants you would use Loctite 592 Teflon PS/T Pipe Sealant on those threads.

PERMATEX PST® PIPE SEALANT W/TEFLON®* – HIGH TEMPERATURE (59214) is the same product. Loctite owns Permatex and markets Loctite products to the consumer under the Permatex name. Products marketed for commercial use go under the Loctite name.

Those thru-bolts have O-rings at the case parting halves that are supposed to keep oil splash from penetrating thru at the nuts. This is also true of those thru bolts which are used for cylinder hold-downs.
Sometimes they leak. (Especially after cylinder changes, because the un-torqueing/re-torqueing disturbs that O-ring.) A fix that has worked well for me has been to thoroughly clean the shaft of the bolt as it exits the case with solvent or electric contact cleaner, etc., then to run a bead of Permatex Aviation #2 around it beneath the flat washer (ie at the case) and then reassemble.
In the case of the two thru bolts below the crank...do only one at a time... so that only ONE is un-torqued at any given moment. (Help prevent bearing-shift or loss of bearing-crush which in turn can lead to a spun bearing.)

George he said forward facing which is why I suspect Kyle is talking about the pipe plugs that plug the end of the oil galleys. These are the threads to which you would use Loctite 592 Teflon PS/T Pipe Sealant or equivalent.

You of course would be correct if we were talking about the through studs or bolts.

I must have focused on the cyl-base leaks he referred to and not noticed he was discussing pipe-plugs. Thanks.

Actually you are both on track - and thanks for the information. Before we install the cylinders I'll use that trick on the bolts. That tip on preventing the bearing from spinning was excellent - anything to prevent problems in the future is a huge help.

More to follow...

Kyle wrote:Actually you are both on track - and thanks for the information. Before we install the cylinders I'll use that trick on the bolts. That tip on preventing the bearing from spinning was excellent - anything to prevent problems in the future is a huge help.

More to follow...

Continental has a specific procedure for torquing cylinders. That information along with torque values for just about every fastener on every TCM engine is specified in Service Bulletin SB96-7C. Access to a partial collection of other Continental service info is at http://tcmlink.com/servicebulletins.cfm. Interesting reading if you have a little time.

Miles

I installed the BAS tail-pull handles yesterday. Although I fit OK back there it was still a bit of a challange. The instructions from BAS are fine. The steps were as follows:

1) Clean sprayed undercoating off inside skin area to receive parts.
2) Place handle tube in position and mark holes, reference points etc.
3) Drill from inside and cleco (used cleco's for the first time )
4) Once the 6 holes per side are done - mark center of the holes by
drawing intersecting lines between the holes on the outside and drill
3/8 hole in the center.
5) Use a die grinder to enlarge center hole for pull handle - hint, vacume
as you go so you can see the edges.
6) Once holes are set, remove unit and debur.
7) Sand unit flange faces and area on skins that flanges contact.
Prime flanges and skin
9) Re-install, cleco and drill final size #30 bit. exchanging clecos to next
size.
10) Remove unit and debur.
11) Re-install, Rivet with supplied rivets. (Used a bucking bar for the first time that was cool )
12) Prep and paint skin / rivet heads as needed.

It was a fun job and the A&P was happy with my bucking. Only pain was having to crawl in and out so much. Total time was 4:15 with a soda break. Someone who has done more of them might do it in less time - not sure.

I'll keep updating as we go...

Kyle

Did anyone take a picture of you back in there?

Nope - but then again, if you've seen one ---hole (I mean sneaker soles) you've seen them all