| BF (4.0) Dipstick blow-out fix [message #302754] |
Tue, 28 June 2016 10:42  |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
Our otherwise great Onan erupted into a cloud of smoke at the fireworks. I shut it down promptly.
The dipstick has gotten so loose in the tube that not only does it not seal, but the crankcase pressure will easily blow by it.
I wrapped it with teflon tape and put it back on-line as it was a hot night. This worked, but I know it won't last long.
The seal does not look replaceable. JimK might have new, but the shipping would have to exceed the part cost.
Does anybody have a plan to make the dipstick stay tight?
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
|
|
|
|
|
|
|
|
|
|
|
|
| Re: BF (4.0) Dipstick blow-out fix [message #302884 is a reply to message #302754] |
Thu, 30 June 2016 13:02  |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
|
Senior Member |
|
|
Another option: Clean the dipstick with carb cleaner on both sides. Coat the tube with vasoline, then put a small dab of RTV silicone on the stick. Once it sets up, remove and clean off the vasoline. Custom made seal.
I have also seen racers use a thumb screw type hose clamp to secure it
76 Glenbrook
|
|
|
|
|
|
| Re: BF (4.0) Dipstick blow-out fix [message #302972 is a reply to message #302754] |
Sat, 02 July 2016 20:24 |
 |
John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
|
Senior Member |
|
|
Matt:
Small engines such the Onan use a PCV System that tries to keep a slight vacuum in the crankcase. That lower pressure helps to keep oil from going up the oil rings. (Small engines will burn more oil and leak more oil out gaskets without the low pressure) The PCV system uses a disk valve and spring that exhausts crankcase pressure on the down stroke of the piston and closes on the upstroke of the piston creating the vacuum in the crank case. Your blowing out of the dipstick is a indicator to me that the crancase is pressurizing and the PCV system may be inoperative or ring blowby has become bad enough to overwelm the system. My suggestion is to remove the breather plate and check and service the valve. This may help your problem, but you also do not have a seal which is also necessary for the PCV system to work.
If the crankcase is not properly sealed. The PCV system begins to move a lot of air into the carb. The high volume of air will bring oil mist from the crancase to the carburetor which will burn increasing the oil consumprion of the engine.
That PCV sytem is sure a bigger part of the engine operation than most are aware of, HUH??
Here is an illustration of the PCV Valve.
http://www.gmcmhphotos.com/photos/discussion-photos/p57964-onan-crankcase-vent-valve.html
I actually was a Briggs and Stratton/ Tecumseh, Clinton, Toro, and MTD dealer a long time ago)
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
|
|
|
|
| Re: BF (4.0) Dipstick blow-out fix [message #322360 is a reply to message #302754] |
Sat, 19 August 2017 15:55 |
cbryan
Messages: 451
Registered: May 2012
Location: Ennis, Texas
Karma: 3
|
Senior Member |
|
|
Peer,
Amazing amount, awesome amount, of help available here, isn't there? There's the short term, medium term fix and a picture of a long term fix already mentioned here. Short- wedge the dipstick. Medium, wrap with tape. Long -find out why the breather doesn't seem to be functioning.
Carey
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
|
|
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
.