Please Describe The Pressure Test For Gear Case Seals

[Demiandvm]

I heard mentioned a test for gear case seals by using a bicycle pump to pressurize the gear case using an inner tube nipple? How does one do this? Are leaks easily noted or is it a leak down thing? Thank You!<br /><br /> Michael

 

[MarkHPCA]

Re: Please Describe The Pressure Test For Gear Case Seals

What I did for mine was to attach a tube to the fitting that comes with one of those kits to fill the oil in the gearcase. The one that screws into the gearcase. I put a 'Tee' fitting on the tube and attached a schrader valve on one side of the 'Tee' and the water pressure gauge from the boat on the otther. I then used a bicyle pump to pressurize the gear case, coonected to the schrader valve, to 22 PSi. If all the seals are good it should hold this pressure for at least 30 minutes. If not then put the gear case under water and look for bubbles to find the leak. <br />This test will check one set of seals. The shafts have two seals on each , one facing in and one facing out. The intention is to stop water getting in AND to stop oil getting out. To test the aother set you do basicaly the same test but this time with a vacuum instead of pressure. If you have a leak then use some grease on the various seal to determine which one leaks. Hope this helps and is not too confusing..

 

[wilde1j]

Re: Please Describe The Pressure Test For Gear Case Seals

Do not exceed 15 psig, or you will for sure be replacing seals which may have been good. Also, LU MUST be drained first, or gear oil will mask results. Auto parts places have a manual vacuum pump for brake bleeding which works well for the vacuum test. Should have some pressure/vacuum after 45 minutes, and some leakdown is OK.

 

[MarkHPCA]

Re: Please Describe The Pressure Test For Gear Case Seals

WildeOne you'r right I stand corrected. According to my 1986 OEM shop manual ...Pump pressure upto 2-6 PSI if it holds then increase to 18PSI. For the vacumm test pull 3-5 in of mercury , if ok then goto 15 in of mercury vacumm. I rented a vacumm pump from a local auto parts shop for about $5.<br /><br />On mine the first time I only pressure tested at 12 PSI and all seemed fine but the gear case still leaked. I went to higher in pressure for a second test and it failed at about 15 PSI at the inner drive shaft seal so at least goto 18 PSI.....Just my 2c