Author Topic: The brass tube for the oil pressure switch  (Read 389 times)

Offline BobAllwine

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The brass tube for the oil pressure switch
« on: May 16, 2020, 05:49:00 AM »
I found out that the brass tube at the back of the block is cracked at the base. This is on my 87 k2500 5.7 ltr custom deluxe.  It has been leaking oil rapidly onto the transmission and then onto the crossover exhaust.  I have had a heck of  a time finally locating the source of the leak.  I haven't been able to locate this part at any parts store and wouldn't have even suspected it as the source of the leak, if I hadn't read about 3 posts on here about it earlier today. It is a thin tube that goes from the block up to a square fitting and then a 90 degree angle to the OPS.  Can I just get a brass tube the same diameter and thread it on both ends?  I already have the switch on order.  I used a small dab of JB Weld Quick just on the tube as a temporary fix. The crack in the tube was big enough that I could stick my fingernail into it.  This is my work truck for my tree service and my transportation for everything else.  Second 3/4 ton Square body that I have owned and I keep getting offers to buy it or trade it for newer pickups.  Not happening. 

Offline VileZambonie

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Re: The brass tube for the oil pressure switch
« Reply #1 on: May 16, 2020, 06:13:13 AM »
You'd be better off skipping the JB weld and removing the pipe/tee. You can go to the hardware store and make something up, just bring what you have with you to try and get something dimensionally close made up. 1/8" brass pipe, 45° or 90° etc depending on how many ports yours has.
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Offline BobAllwine

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Re: The brass tube for the oil pressure switch
« Reply #2 on: May 17, 2020, 08:52:52 AM »
Thank you.  It still had a leak, but not near as bad as it was.  I will go to Ace Hardware later this morning and get a short brass tube and cut the threads and then replace the piece that has crack. 

Offline BobAllwine

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Re: The brass tube for the oil pressure switch
« Reply #3 on: June 21, 2020, 07:27:24 PM »
I no longer seem to have the problem of the brass tube for the oil pressure switch leaking.  I am swapping out motors for my 87 chevy 3/4 ton 5.7l tbi.  Pulled the motor and tranny and I pulled the front seal out of the thm400 tranny since it was leaking as bad as a rear main seal would.  Once it was pulled, I found what looks like a large washer about 3/8ths of an inch wide and it is cracked and looks like it has a separation of about a 1/4 inch. I should have taken a photo to put on here, but was told by someone where the front transmission seal was purchased that this wont be a major issue, and now there is a new seal covering that broken ring. 
The brass tube wasn't cracked like I though it was and thought it showed with a mirror. Turns out it was where it reduced in size for the threads that mount into the block.  It was leaking at the back of the valve cover gasket on the left bank of the engine.  Took care of that.

Offline BobAllwine

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Re: The brass tube for the oil pressure switch
« Reply #4 on: July 01, 2020, 01:02:42 PM »
Took the tranny to a shop and found out it is a weep hole that is supposed to be there. Learned something new about my truck.