[TR] Oil Pressure Loss

Tony Drews tony at tonydrews.com
Sat Dec 24 13:29:38 MST 2016

It's very likely that no damage was done.  The oil pump will flow 
much more oil than can be pushed through the small orifice that leads 
to the oil pressure gauge.  You will have had oil flowing to the 
galleries, maybe not at as high a pressure as normal but enough to 
avoid killing the engine.

Rod bearings would be the first to go - #2, #3, #4, #5 would be worst 
as there are two rods fed by one main bearing.

I'd leave it buttoned up and just enjoy driving it.  If you really 
want to check, drop the pan and check an easy to get to rod that's 
not #1 or #6.

Regards, Tony Drews

At 09:15 AM 12/24/2016, david brady wrote:
>Hi Folks,
>Big blunder on my part. Long story short, I inadvertently started 
>the cold engine with the oil pressure tube disconnected. Runtime 
>maybe 15 seconds with a couple of low rev throttle blips. I noticed 
>a smell so I immediately checked the oil pressure gauge saw no 
>pressure so I  shut off the engine. The smell was oil leaving the 
>engine. I started the engine outside the car with the bonnet open 
>which is typical for me. I need to manually hold the weber chokes 
>shut with my hand as I turn over the engine.
>Here are the particulars:
>1) cold engine
>2) seven quarts of fresh 10w-30 Brad Penn oil in sump
>3) start engine, maybe 15s (probably less) of runtime, no-load
>4) 3 quarts of oil pushed out the oil pressure gauge fitting
>5) engine has cam bearings.
>I replenished the lost 3 quarts of oil, started the engine, and went 
>for a 20 mile drive. No external signs of anything wrong. Engine runs great.
>Several questions:
>1) with the oil pressure loss out the disconnected fitting is there 
>any chance of even a dribble of oil being fed to the oil galleries?
>2) I understand about oil flow rate being important and about the 
>hydrodynamic oil film required with plain bearings which actually 
>generates the oil pressure in the bearing's oil film itself. I'm 
>more concerned about the heat buildup at the bearings due to lack of 
>flow. What are the chances of bearing damage due to heat buildup in this case?
>3) which bearings would be the first to show damage? Main, 
>connecting rod, cam?
>4) is it recommended to drop the sump and roll out a bearing to 
>check condition?
>Here's how it happened: a month or so ago I was testing the accuracy 
>of my oil pressure gauge so I bolted on a new gauge. I then ran my 
>tests and disconnected the tube from the crankcase in preparation to 
>reconnect the stock tube, but I was then pulled away from project 
>and failed to reconnect the stock pressure gauge tube. Fast forward 
>a month and I completely forget that the engine's not buttoned up 
>and I start the engine! Yikes!
>Thanks for your input,
>Merry Christmas,
>'68 TR250
>** triumphs at autox.team.net **
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