Greetings from a longtime lurker. The short and dirty - I'm blowing crankshaft seals and can't figure out why. Brand new (although it had been in the crate for 15 years by the date codes on it) JD Short block assembly with less than 10 hours on it since rebuild. Head was remaned by a local machine shop. Head bolts were torqued to spec and all valves adjusted to proper clearances. i've blown two sets (front and rear) of seals within an hour on the machine. Factory install tools were used to install them both times. I don't have access to the tool necessary to check for cylinder pressure leaks at this time. I've checked oil level and it's where it's supposed to be, though I don't know what the oil pressure is because I have a voltage issue that causes it to read off the gauge (I'm getting 5v to the sensor and it's only supposed to be 1v) I'm seriously tired to taking the motor out on this thing and dumping money into it. Suggestions welcomed.
Crankcase vent is plugged.
It's an 3/4" open tube connected to the valve cover - no PCV valve system on this unit. I've checked the tube a half dozen times.
Are you sure the tube is clear all the way? What about the internals of the valve cover? Was crankcase pressure checked?
You could plug the vent hose momentarily with your hand to see if feel any pressure build up, with the engine running. The screen thingy inside the valve cover could be plugged. For curiosity sake, remove the valve cover and take a look.
Valve cover came off to adjust the valves when I replaced the seals the second time - its all clear.
Valve cover internally is spotless. I cleaned it out when I put the new motor in 10 hours ago. The tube is only two feet long and I can see straight through it. The elbow is also clean. I don't have a manometer to check the pressure, though I'm looking into it. Think the ol' balloon over the dipstick trick would work?
Easy enough to make one.
I've not yet had time to check the crankcase pressure, due to work, family, and the weather, but I did run across something I thought could be a part of the problem. My tech manual details replacing the seals with the adjoining covers already installed (as in replacing a faulty seal) and not a complete rebuild of the motor to include removing the timing cover, etc. I ran across several other posts (about differing engines) where they indicated the adjoining covers were installed, but the bolts weren't tightened more than enough to slightly hold the cover - thus allowing it to move a little one way or another when the crankshaft seal was installed. I had previously installed both covers and tightened the bolts to torque spec. They then sat several weeks until I could get the install tool for the seals. Is it possible the timing cover is off center enough to affect the integrity of the seal? I'm still gonna run with checking the crankcase pressure first, but trying to keep other possibilities in mind, too.
Seriously, if there was enough base pressure to push out seals, you wouldn’t need a gauge to measure it. Your thumb over the crankcase vent tube be adequate. .
It should have been doweled to prevent that as well as the flywheel housing. If both have been torqued correctly that leaves - 1. Excessive Blow-by 2. Excessive crank end play and/or vertical movement (I've seen vertical movement on the larger Deere engines from a shot rear main bearing, but not on the small ones.....yet) or 3. Seal installation error But just in case, when you remove the seals to replace them check concentricity of the crank to the housings with a dial indicator to rule out that issue (there is not a published spec for this engine).
Bent crankshaft.
Concentricity check would confirm what granpa said ^^^^.
What type of seal are they? Do they come with a wear sleeve? What are you using for an installer? Some seals have to be installed with the seal lip and shaft dry. Installing a seal and having it just the slightest bit crooked can be a problem. Your not installing a seal that was designed for a wear sleeve without the sleeve? Can you post a picture of the seal.
First picture is what the latest crank seals look like. The other pictures (first front and next the rear) are what they used to look like and may still available depending on where you get them.
Please don't be offended by my questions. Is there any chance you are installing them backwards ? Do the lips contact the crankshaft like one normally should ? Could you describe "blown seals" ? Just leaking or actually destroying the seal surface some way ?
Not sure how I'd end up with a bent crankshaft on a brand new short block, but I suppose it's possible. Rear one looks like the first one (Part # DZ111672). Front one looks like the second (Part # was RE538097). Both were installed with the manufacturer tools for seal installation - JDG954 for the front and JDG476 for the rear. Both seals were installed try and surfaces were cleaned thoroughly with brake cleaner and allowed to dry before seal installation. They are installed properly. Both seals designate which side is "out". The lips contact properly, the problem is oil is still leaking through the seal. As best I can tell, something is causing the oil to be pushed through the rubber seal between the inner and outer portion of the seal. I certainly appreciate the feedback and no offense has been taken. Please, keep the thoughts coming.
Do the serals come with an instillation tool? How are you installing them?
See post above yours.
JDG954 is correct for the front seal. Rear seal installation tool should have been JT30040B. JDG476 is for the 8.1L and 9.0L engines.
How much end play is there on the crankshaft?
You should be able to remove the oil pressure sensor, and with the proper fittings hook up a PSI gauge to check that oil pressure. I know nothing about Deere engines. But, I do know it has a balance shaft geared to the crankshaft. Hopefully it is there and timed correctly. I believe bad things happen if they are not timed correctly. IMHO.
Both balancer shafts are present and properly timed. I bought the timing tool to time it when I put the new short block in.
I would like to see a pic of the blown seals.....while still in the cover if possible. Something isnt making sense to me.
That makes two of us. It's probably going to be a couple weeks before I get the motor back out of it. Basically, I've got a steady leak from the bottom of both seals. Very irritating on a new motor. I followed the CTM104 manual during the rebuild.
Ditto.
**UPDATE: This evening I fired up the 270 to move it after a break in the wet weather. The wife had asked me to level out a small area I thought would take about 10 minutes, so I began moving some dirt. As a near the finish, I lost hydrualics. After turning the machine off I discovered the fluid leak I initially believed to be the rear main seal is a leak somewhere in the main hydrualic pump. The hydrualic fluid and the break in oil were so similar in smell, color, and consistency, I believed it to be engine oil. All that said, it does appear the front seal is still leaking. More to come...