Oil Voids in Oil Lines

[grumpy56]

Hello All. Have had my 1970 T350 on the road now for a month or two. Runs good, seeps just a little gas, but fun to run around on close to home. Did notice that I had some "gaps" in the oil lines. When I put new lines on back when, I primed them and they seemed to be fine until last week (and today). Probably have put around 100 miles on it. There was a 1/4" gap in one line last week and another one (different line) today. Any ideas on why this is happening and if I need to do something? Thanks.

[Craig380]

Unfortunately, I think you will need to sort it out. First check the banjo bolts holding the lines to the cases are snug. If they are OK then it could be the lines have a leak where they connect to the banjos. These can be siliconed CAREFULLY to stop them sucking air.

[tricky1962]

From my experience, there are two causes:

1. Leaks in the oil lines, which could be sealed with silicone sealant, or in my case two pack epoxy. The internet suggests that most leaks of this type occur at the junctions with splitter - where one pipe splits into two

2. Dodgy check valves. I had a dodgy check valve, as evidenced by having sealed joints - see above - bubbles still present. Being a bit tight with the cash, I purchased a pair of new check valves for the one cylinder. This solved the problem for that cylinder, by moving the bubbles over to the adjacent cylinder. Clearly the valves should have been replaced as a set, because changing the other cylinder's check valves solved my problems.

I would seal all the joints in the pipework with epoxy or silicone, then if that doesn't solve the problem, buy new check valves

[grumpy56]

Appreciate the help. Will check it out to try to find my leaks.

[Glyn.G]

Hi,
I have been rebuilding a GT380 motor that had the same problem as your T350. I purchased 6 new check valves then I primed the 6 lines and pumped some oil through by running the pump by a cordless drill to remove any air in the lines, you can see the air bubbles moving along the lines until they are pushed out at the check valves. Then I double checked the next day by the same method and again there was air in the line. After a lot of searching I found that although the oil seal on the base of the pump seemed fine it had hardened and was letting air past at certain revs ( Ok at low revs but let air in at higher revs ). I know the pumps are different but I believe the T350 pump also has a small seal on the drive shaft.
May be worth a look if you're still having problems after checking all other options.

[jabcb]

Forum member bloop2 sells rebuild kits on eBay that have all of the o-rings & seals to rebuild the pump.
But be careful with the priming bolt on the top of the pump — it has reverse threads!

[Vintageman]

Other than what was said so far (check valves, poor seal of banjo fitting, etc) it can be the pump seals and O' rings sucking air.

[grumpy56]

Thanks all. Will look at all of the above.