Compression Test...Can someone tell me what's next...
 

I did a compression test on my 914 2.0 D-Jet. I received the following readings:

Cylinder #1: 145
Cylinder #2: 145
Cylinder #3: 100
Cylinder #4: 160

I did the test with all spark plugs pulled, coil wire pulled and at full throttle. I would appreciate any advice on what to do next. I know #3 is pretty low. Should I start getting ready for a rebuild and what should I rebuild? Again any advice is greatly appreciated.

Thanks,
Rod

________________________________
1974 914 2.0 D-Jet

The Haynes manual says that the maximum permissible difference between cylinders is 21 lb/in^2 so you do seem to have a problem. A leak-down test will give you a much better idea of what the problem is. You can find more info here .

Try adjusting the valves and re test first. Sounds like a tight valve to me.

Geoff

You can diagnose valves vs rings by re doing the test "wet". To do a wet test you add a few drops of oil and retest.

if they come up much it is rings, if not valves.

I adjusted all the valves to spec before the test. If I did have a tight valve, would it be cylinder 3 or 4? I will also try to re-test with oil. Thanks again for the help...

It would be #3 since that's the low cylinder.
Try the wet test to eliminate the possiblity of a cracked ring or scoring of the cylinder wall. My guess is a valve that is burnt from being too tight.
Geoff

Geoff, what am I looking for when I do the wet test. When I put a teaspoon of oil through the spark plug hole, what do I do next...Sorry but I am new to this. Again thanks...

Rod

You should make sure the engine has warmed up fully if possible before you do the compression test too. Do a "before adding oil" compression test and be sure to count the jumps the gauge takes to top out. Then add the shot of oil and test each cylinder again. If the low one has jumped up then it is probably the rings that are worn and the oil has sealed them some. I agree with the previious post about making sure the valve adjustment is right on spec before you do the testing and insure the batt is fully charged. Good luck

Okay, just did the test wet. After doing a dry test, cylinder #3 was still at 100. I then squirted some oil into the cylinder and at first it jumped up to 105. I then tried the test again and squirted some oil into #3 again and it jumped up to 125 and held there. Is this bad? Is it time to rebuild? Thanks for the help guys, I really appreciate it.


Rod

I'd say that is a ring problem.

It is harder to do a wet test on a flat type of engine, it probably took the second shot and a few spins to distribute the oil fairly evenly. It's still a bit low thhough.

If it runs well otherwise, you could probably just replace the P/C's and inspect / grind the valves. You might even get away with just rings / gaskets.

I have this bad habit of letting stuff snowball though, so I'd go through the whole thing.

What does the plug look like? If its all oily and black then maybe I would say the rings are bad in that cylinder. Maybe the cylinder walls are scored?

Hmmm, worth taking a look at before something really bad happens.

I changed the plugs about three months ago and they look fine.............I know the pics are probably overkill, but I'm trying to explain this stuff as best I can. Thanks for all your help..
http://forums.pelicanparts.com/uploa...1062816779.jpg
http://forums.pelicanparts.com/uploa...1062816800.jpg

Thanks again

re-ring. check end play on teh crank to determine condition of bottom end.

Leakdown test anyone?

Next thing, junk the platinums! Use the regular plugs or copper cores instead of those things.
I'd go the leakdown test next.

Geoff

Sounds like I'll be doing the leak down test next. Can you guys let me know how. I've heard you can put together your own, is this true? Thanks again............

Oh, I forgot, I'll trash the platinums...Your like the third person to tell me that, so out they go.....

I'll be the 4th............get rid of the platinum plugs,they don't work well in our engines............get the Super Bosch they work better!

Set that piston at TDC, put it in 5th gear with the parking brake on and wheels chocked.
Pull the valve cover off of that side.
Hook up a pressurized air source through the spark plug hole and put air pressure on that cylinder.
Listen for the air leak. If it is going out the exhaust pipe you have a bad exhaust valve. If it leaks out the intake, bad intake valve. if it blows out from the crankcase breather, bad rings. If it blows out the head where the valve cover normally is, it's leaking valve guides.
A little leakage into the crankcase is normal, but a lot is not normal.

DIY Leak Down tester

I bought one from these guys:

https://www.carshopinc.com/

But the site seems to be down right this second.

$53

James

You guys are great, thanks for the help and I'll give it a try...

Rod

Count me in on the toss the platnium's,

I wasn't going to say anything, but since we are all piling on.........

:D

Yep, the platinums are gone.......Hey nice RC51

how do I go to see the RC 51 pics?

The RC 51 pics are here:

http://www.bellsouthpwp.net/d/u/duckryder/

Most of them are in the "Akrapovic" directory.

Ok, I'll be dropping the engine on Saturday. I found these on ebay:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&category=33623&item=24 31263197

Will these work. I'm gonna pull the heads, change the pistons, rings and cylinders. Change the valves and what ever you guys suggest I do. I really dont want to split the case though. Again, thanks....

Rod

Anybody, anybody...please.....

Work? Yeah, sounds like they oughtta. How right they'll be? What kind of quality they are? Total unknowns.

--DD

Thanks, Dave...I'll keep searching...Hey, Dave...I see PP has both the Euro and US P/C's...Would it be advantageous to purchase the Euro?


Nevermind, just read the PP article reference the difference.

Rod

Got the head and cylinders off for 3 and 4....here are some pics. Could you tell me what you think.
http://forums.pelicanparts.com/uploa...1063506651.jpg
http://forums.pelicanparts.com/uploa...1063506665.jpg

Thanks
Rod

Is the sealing ring on #3 broken at around 2 O'Clock?

Hard to see in the photos what the pistons and rings look like.

Couple of better photos of the cylinder walls and pistons would help.

Any Scoring in the Cylinder or on the Piston?

Does not appear to be any scoring on the walls at all. #3 cylinder has some kind of black mark (some type of build up) I think. Here some more pics and I will take more tomorrow when I get the pistons off.

Thanks for the help.
http://forums.pelicanparts.com/uploa...1063508184.jpg
http://forums.pelicanparts.com/uploa...1063508218.jpg
http://forums.pelicanparts.com/uploa...1063508293.jpg

Here is what jumps out at me:

1) it looks to me like the heads have the seal rings in them and the #3 is blown at about 2 o"clock near the head bolt. (#3 Jug seems to have discoloration in the same area.)

2) again a little hard to see, but either the piston resting on the studs has pushed the # 2 ring way up and is creating an optical illusion, or the ring land is broken away. (The more I look at it the more it looks like an illusion)

3) if those rings were aligned that way while running, the gap in the #2 and the oil ring (the thick one) is way too close together.

How's your oil pressure?
IMO, splitting the cases and doing the bottom end is the cheap part, pistons, cylinders and head work is where the bucks are, and you're gonna be putting new wrist pins into old rod bushings...
If ya got the thing this far apart, and you decide to get new Ps and Cs AND the miles are getting up there, pull it right apart, take the crank, rods and case it to a machinist get them to measure and clean everything. Then you clean it again and reassemble it. It is not difficult (I did it, first engine rebuild.)
BTW - Dave D told me (nearly three years ago now) when I began my project that my cam would probably be badly worn. It was toast. I have no regrets at all about doing the complete rebuild.
Best of luck. Dave

What did you decide to do?

Well, glad you asked. I dropped the motor on Saturday and brought the heads, cylinders and pistons to a friend of mine who owns his own shop (The Sports Car garage, Palm Desert, Ca). He disassembled the heads for me and told me that the valve guides are shot.

He showed me that the valves are floating around in the guides. He told me that the pistons, cylinders and valves are all in great shape, but I needed new rings. So I dropped everything off at the machine shop for cleaning and a valve job. The machine shop guy also told me that the cylinders, valves and pistons are all in great shape. So I immediately ordered new valve guides, valve springs and other stuff from Pelican Parts.

My buddy at the garage suggested I should split the case and change the bearings and check the cam and other things. But to be honest with you, the more I look at the case, the more that thought scares the **** out of me. I just dont want to mess the case up. Anyway, I'm still pondering the thought, maybe I will and maybe I wont. Again, I want to thank all of you for your advice. Couldn't have gotten this far without it. Can't wait to put everything back together.

And one more thing.....while taking off the oil filler, I looked inside and found a black cap just sitting there inside where you pour the oil...it's part number 022 115 486....I did a search through PP and found that it is a plug.......Does anyone know where this goes?

One thing about splitting the case - you will need an engine stand. There are actually very few parts in there, but if it spooks you, why don't you get the garage to quote on doing the bottom end for you?

Dave

Good point Dave...I just wanted to maybe do it myself, but I guess I can always have the garage do it for me. But knowing me, I will probably end up splitting it myself this weekend.

Thanks,
Rod

Splitting it isn't a huge deal. (Of course mine is still apart, so who am I to talk) You can pretty much bet it needs a cam, they all do for the most part.

As long as someone previously didn't do something stupid, once you get all the bolts out it the case halves will come apart without too much effort.

Sounds like you are in pretty good hands. If it gets into valve and seat work, have someone who really knows these things do the work. Also, the exhaust valves are sodium filled and have a reputation for dropping. It would be worth considering replacing them with stainless.

Go for it.
I made an engine stand bracket, cheap (and flawed, don't copy it without talking to me first). Had the machine shop measure everything, clean the case re and re the rods, polish the crank, balance everything, I bought new cam, lifters, bearings and checked oil clearance and reassembled. followed Jake's video and Tom wilson's book. No problems. You wouldn't want to do all that, but checking/replacing the cam, maybe polishing the crank and and replacing the bearings might be money well spent.


http://forums.pelicanparts.com/uploa...1063939729.jpg http://forums.pelicanparts.com/uploa...1063939742.jpg