KevTech
09-19-2004, 11:55 PM
Well boys, I think that I have fiigured out why the CAT 0750 fuel filter in the PRE or POST setup had been giving many problems with an air leak.
Earlier this year I created the following post showing a PRE or POST bypass fuel filter setup:
http://dieselplace.com/forum/forum_posts.asp?TID=4160&PN=2
Many people tried this kit with problems of unresolved air leaks. Many thought it was the CAT head & many thought it may be the hose connections. Then there were a few lucky people like myself that never once expeienced an air leak with this setup. UNTIL RECENTLY....
After 10,000miles of perfect use without an air leak or any problems at all, it was time to change the CAT0750 fuel filter.
I spun off the old filter, installed the new filter, primed the unit & started up the truck. All worked fine until I shut off the truck & came back the next morning to find that it would stall out when trying to start!
I primed the fuel line again & the truck started right up & worked fine all day. Then once the truck was shut off for more than an hour it would stall out when I tried to re start it.
I knew that nothing was wrong with my bypass fuel setup so I thought there may be something wrong with the CAT filter since that was the only thing that had changed since the air leak problem started.
I spun off the filter & examined it with no visible clues at to why I was experiencing an air leak. I lightly greased the CAT filter gasket thinking this may help & then spun it back on. This time I turned it a little tighter thinking this many give it a better seal. I primed the unit & the truck started right up.
After driving the truck for a couple hours & then letting it sit, I went to start it back up & experienced the exact same air leak problem with the truck stalling out!!
I was stumped.....Why was this unit giving me such problems when nothing had changed except the new filter? After pondering some time without avail, I went to take the filter off. This time it was a little more tough to spin off since I turned it on a little more tight with the last install.
Guess what I had seen? As the filter started to slowly truning off the CAT head, the rubber filter gasket was not moving while the filter was spinning. Yes, the filter gasket had a nice tight seal against the CAT head but was turning loosly between the gasket & filter base groove.
Once the filter was totally removed, I examined the gasket & all looked normal. Then I removed the gasket from the filter with little effort & noticed that there was quite a bit of diesel between the gasket & the groove that it sat in on the filter base.
My theory is that with the vacuum pressure build up in the fuel line, air was being drawn in between the CAT fuel filter gasket & the fuel filter groove that the gasket sat in, after the truck was shut off each time.
I cleaned the head of the fuel filter & gasket groove with a rag. Then applied a thin layer of grease to the groove on the end of the filter before pushing the rubber gasket back into place. I applied a thin layer of grease to the outside of the filter gasket & spun it back onto the CAT filter head.
Started the truck up & have not yet had an air leak of any kind since. I have a feeling that no matter how tight the filter is spun on, air was leaking into the system between the CAT filter groove & the factory rubber gasket that is sitting in that groove.........................A thin layer of grease seems to have solved everything.
Earlier this year I created the following post showing a PRE or POST bypass fuel filter setup:
http://dieselplace.com/forum/forum_posts.asp?TID=4160&PN=2
Many people tried this kit with problems of unresolved air leaks. Many thought it was the CAT head & many thought it may be the hose connections. Then there were a few lucky people like myself that never once expeienced an air leak with this setup. UNTIL RECENTLY....
After 10,000miles of perfect use without an air leak or any problems at all, it was time to change the CAT0750 fuel filter.
I spun off the old filter, installed the new filter, primed the unit & started up the truck. All worked fine until I shut off the truck & came back the next morning to find that it would stall out when trying to start!
I primed the fuel line again & the truck started right up & worked fine all day. Then once the truck was shut off for more than an hour it would stall out when I tried to re start it.
I knew that nothing was wrong with my bypass fuel setup so I thought there may be something wrong with the CAT filter since that was the only thing that had changed since the air leak problem started.
I spun off the filter & examined it with no visible clues at to why I was experiencing an air leak. I lightly greased the CAT filter gasket thinking this may help & then spun it back on. This time I turned it a little tighter thinking this many give it a better seal. I primed the unit & the truck started right up.
After driving the truck for a couple hours & then letting it sit, I went to start it back up & experienced the exact same air leak problem with the truck stalling out!!
I was stumped.....Why was this unit giving me such problems when nothing had changed except the new filter? After pondering some time without avail, I went to take the filter off. This time it was a little more tough to spin off since I turned it on a little more tight with the last install.
Guess what I had seen? As the filter started to slowly truning off the CAT head, the rubber filter gasket was not moving while the filter was spinning. Yes, the filter gasket had a nice tight seal against the CAT head but was turning loosly between the gasket & filter base groove.
Once the filter was totally removed, I examined the gasket & all looked normal. Then I removed the gasket from the filter with little effort & noticed that there was quite a bit of diesel between the gasket & the groove that it sat in on the filter base.
My theory is that with the vacuum pressure build up in the fuel line, air was being drawn in between the CAT fuel filter gasket & the fuel filter groove that the gasket sat in, after the truck was shut off each time.
I cleaned the head of the fuel filter & gasket groove with a rag. Then applied a thin layer of grease to the groove on the end of the filter before pushing the rubber gasket back into place. I applied a thin layer of grease to the outside of the filter gasket & spun it back onto the CAT filter head.
Started the truck up & have not yet had an air leak of any kind since. I have a feeling that no matter how tight the filter is spun on, air was leaking into the system between the CAT filter groove & the factory rubber gasket that is sitting in that groove.........................A thin layer of grease seems to have solved everything.