M90 Snout rebuilt

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immortality
Posts: 3416
Joined: Thu Apr 09, 2009 12:31 pm
cars: VH, VN, VS, VX

M90 Snout rebuilt

Post by immortality »

Hi Guys,

Anybody have any experience rebuilding the snout on the M90?

I've already got a new coupling and oil but figure while I have it apart I may as well do the snout bearings.

So far I've found a few bearing numbers. 6203 C3 and 6204 C3 and seal 20x47x7mm all of which I should be able to get at my local engineering supplier.

Does anybody have any instructions for rebuilding the snout?

Thanks
Xnke
Posts: 33
Joined: Thu Sep 24, 2015 1:42 pm

Re: M90 Snout rebuilt

Post by Xnke »

I have done it many times. I even have had to build jigs to shorten/lengthen the nosedrive to suit other vehicles-these blowers are just so cheap that it's silly to not use them in conversions.

First, drain the oil outside and away from animals. It's NASTY. The new oil isn't bad, but the old stuff...rancid!

You will need the anerobic sealant, plain old RTV won't cut it. Permatex makes one in a blue tube, red gel. It's not cheap or easy to find.

Once you unbolt the nosedrive, you'll need to knock it off the front of the case. It's on hollow dowel pins on some M90's, and solid pins on others.

If you have press-fit pulleys, you need to use a dedicated puller. Even my 40 ton press wouldn't do the job without damaging the pulley, and it has to come off.

Once the drive has been separated from the rotor plate (DO NOT try to push the rotors out of the rotor plate!) you can pull the rotor plate by tapping from the inlet opening and push the rotors and rotor plate out. You can hydraulically remove the rotor needle bearings from the case easily, and they push right back in-but they are harder to get these days as INA (the manufacturer) is under fire from Eaton to not sell them to anyone but Eaton. You can set the rotor plate aside for now-rebuilding the rotor assembly is for the "advanced course".

The nose drive breaks down pretty easy-once the front pulley is off, and the drive has been removed and flushed out with some brake cleaner, remove the front seal retaining clip and the nylon/plastic drive coupler from the 3-pin drive. You'll know it when you see it, they are inexpensive now on ebay and even at my local parts stores here in the US.

Once the clip is out, and the drive coupler has been slid off the pins, you can press the shaft out of the front bearing and seal, or use a sacrificial wood block and tap it out of the front bearing with a mallet. Don't try to drive it out by beating on it without a soft block to save the front of the shaft. It's a real bad day if you manage to deform it. It should take very little force to move the shaft.

The rear bearing will come out with the shaft, as well as a big spring. Now, you have access to the inside of the nose drive, and can press or knock the front bearing and front seal out from inside the nose drive. Easy to change this one!

The rear shaft bearing is captive on the shaft-and it's a slightly tighter press fit. You will need to first press off the drive plate-it's pressed onto a straight knurl and it is TIGHT. You need to use a press for this if it's at all possible. If you can't use a press, well, be extra careful. Use soft punches.

Once the drive plate is removed, you can press the bearing off the shaft-it's not as tight as the drive plate and no knurl, so easy to do. Press the new bearing back into place.

Next, grab the drive plate and align the knurl marks with the shaft-this acts kind of like a spline, but the splines are NOT going to self-align! If this is not lined up pretty dang close to correct, it will not be as secure and it's possible to strip the knurls out-only had this happen once so limited data on if it goes bad. It's not as hard as it sounds, but the knurl marks are very small.

Now, you can press the new front bearing into the snout, and set a large deep socket on the OD of the front snout bearing (or use a bit of pipe the right diameter) and you can press the newly assembled drive shaft into the housing-you need to remember that big spring too! It will be pressing through the front bearing and into the housing, and it IS possible to push it too far, but pretty easy to correct it if you do. The rear bearing can be anything from a light press fit into the aluminum snout, to barely snug...I've seen it drop in with minimal finger pressure if it's aligned properly.

Once the front and rear bearings and the shaft are fitted back into the snout, you can press or tap in the front seal and then install the retaining clip.

Before you assemble the blower, get the correct hex key and get the fill plug out. They're generally a pain in the ass and it's easy to strip them-If you strip it or get close to stripping it, a T25 or T30 Torx bit can be driven in with a mallet and then be used to turn out the plug-and as a plus now it's a torx fastener and it's much less likely to strip out in the future. New ones are available on Ebay last I checked-I have a small stockpile of them.

When re-assembling the blower, don't be tempted to remove carbon buildup on the rotors or inside the case. It's beneficial and improves VE by acting kind of like a carbon seal, or the abradable powder coating that Eaton used on the Gen V rotor assemblies. DO scrub down and scrape off the residual sealant from the front face of the case, and both sides of the rotor plate, and the nose drive. There are no gaskets here, the sealant is all you get.

Make sure before you goop the case and the nose drive, that you have installed the plastic drive coupling onto the three pins on the rotor assembly. It's easy to leave out and it's just not going to be a good time if you leave it out.

Use the anerobic sealant on both sets of mating faces-first on the case to rotor plate, tapping the rotor plate home with a rubber mallet and making sure the rotors turn freely in the case. Sometimes you may need to tap the front of the rotor shafts LIGHTLY to get them aligned with each other, this is not particularly common, and you're not trying to move anything, just vibrate things back into position. Once the rotors are back in the case and sealed, goop the nose drive assembly, and slide it on to the dowel pins. DO NOT allow any of the old oil to run across the sealing face-it will leak forever if these faces aren't clean and oil free when you use the sealant. It doesn't take much sealant either, but being anerobic the stuff just wipes off the case after you're done. Never hardens until it's pinched up.

Install the front case bolts and tighten in a random pattern to 18 ft-lbs, basically just snug all of them up and then torque in a criss-crossing random pattern. I don't know why Eaton specifies "random" or how random they mean...

Now, installing the front drive pulley will need a pusher-they thread into the 8mm hole in the snout and push the pulley back on. You can not push the pulley on in the press safely, I have warped drive shafts doing this trying. Yes, the press fit on the pulley (or modular pulley system hub) is FREAKING TIGHT. It must go on till it's flush with the front of the shaft, or the shaft is very slightly proud of the pulley. Then, reinstall the vented front nut (it has a sintered bronze center that acts like a pressure vent) and fill the unit with 8 oz of snout drive oil-available at your local GM dealers in 4oz bottles. The correct oil is GM part #12345982 and even today is readily available at the dealer.

Refit the plug, reinstall the blower to the engine and off you go.
MAGP
Posts: 665
Joined: Tue May 10, 2016 5:48 pm
cars: VC V8 sedan, VS V6 wagon, VT V8 Landcruiser.

Re: M90 Snout rebuilt

Post by MAGP »

Wow excellent write up :thumbup: . Pics would help but it is pretty clear even without them.
immortality
Posts: 3416
Joined: Thu Apr 09, 2009 12:31 pm
cars: VH, VN, VS, VX

Re: M90 Snout rebuilt

Post by immortality »

Thanks for that.

I do have access to a shop press so no issue there. All going well when I do the job I'll take a couple of pics.
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