![]() |
Register or Log In To remove these advertisements. |
|
|
![]() |
|
Thread Tools | Display Modes |
|
![]() |
#1 |
Registered User
Join Date: Apr 2016
Location: Santa Monica, CA
Posts: 18
|
Factory oil pressure gauge fluctuates while braking
Long time lurker, first time poster.
69 c10 with factory cluster. While braking the oil pressure gauge drops. Under, relative, hard braking it will drop all the way down. No audible knocking, oil level good with not old VR1 20w50. Is this just an overly sensitive gauge? Doesn't really make sense unless its just the slosh and the sending unit temporally goes dry? Old pic, pre wheel change now on 15x8 rallyes. |
![]() |
![]() |
![]() |
#2 |
Registered User
Join Date: Jul 2015
Location: North East PA
Posts: 682
|
Re: Factory oil pressure gauge fluctuates while braking
20/50 oil is some thick stuff , what engine is in your truck
|
![]() |
![]() |
![]() |
#3 |
Registered User
Join Date: Apr 2013
Location: South Westerlo, New York
Posts: 1,325
|
Re: Factory oil pressure gauge fluctuates while braking
Is it a fly-by-wire gauge or oil tube fed gauge? My bad, gauge uses tube.
__________________
Thanks, Joe.. 1969 C/10, 348 C.I., 3X2 bbl. V8, 2004r , LWB. |
![]() |
![]() |
![]() |
#4 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,632
|
Re: Factory oil pressure gauge fluctuates while braking
What does the gauge do when you're under extreme acceleration?
|
![]() |
![]() |
![]() |
#5 |
The Older Generation
![]() ![]() ![]() Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,524
|
Re: Factory oil pressure gauge fluctuates while braking
-
Welcome to the board.... I would say that your pickup tube or filter screen has dropped off of the oil pump. My Blue '67 with the 454 would do that when you turned a corner hard or braked hard or accelerated hard. Try putting an extra 1/2 or full quart of oil in it and see what it does. If it doesn't do it then you will need to pull the pan and check the pickup tube/filter. LockDoc
__________________
Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - |
![]() |
![]() |
![]() |
#6 | |
Registered User
Join Date: Apr 2016
Location: Santa Monica, CA
Posts: 18
|
Re: Factory oil pressure gauge fluctuates while braking
Quote:
motor is a 468 big block with unknown internals (purchased the truck with it) |
|
![]() |
![]() |
![]() |
#7 |
Registered User
Join Date: Apr 2005
Location: Cheyenne, WY
Posts: 742
|
Re: Factory oil pressure gauge fluctuates while braking
Under normal driving, the bulk of the oil would be located such that the pick-up tube could get the oil. Under vigorous driving, the bulk of the oil can move to a different location in the pan, moving away from the pick-up tube. The screen moves the pick-up point closer to the bottom of the pan, where some oil may remain even under vigorous driving. If the screen came off, then the tube can't reach the oil when you are under hard braking.
|
![]() |
![]() |
![]() |
#8 | |
The Older Generation
![]() ![]() ![]() Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,524
|
Re: Factory oil pressure gauge fluctuates while braking
Quote:
As far as the pickup tube, what they said ^^^^. And like I said in my previous post if you over fill it with oil that should let you know if that is the problem.... There isn't a sender unless you have a dash panel with lights instead of gauges. The oil gauge is mechanical so the pressure is read directly from the port on the block. LockDoc
__________________
Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - Last edited by LockDoc; 04-11-2016 at 10:32 PM. |
|
![]() |
![]() |
![]() |
#9 |
Proprietor of Dale's Corner
![]() Join Date: Nov 2012
Location: Vacaville , CA
Posts: 16,146
|
Re: Factory oil pressure gauge fluctuates while braking
The pick up tube is designed to pick up the oil from close to the oil pan. The pump intake is submerged without the pick up but not a lot. Corners, braking, hard acceleration can leave it exposed to air instead of oil resulting in cavitation or airation.
__________________
"Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man |
![]() |
![]() |
![]() |
#10 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
|
Re: Factory oil pressure gauge fluctuates while braking
In my '69 with the 307 I'd get the light (non gauge truck) would come on during cornering, and I figured that was related to the pickup tube, but it didn't come on under hard braking, which is weird now that I think about it.
I wound up keeping mine a little overfull, which isn't the right solution, but I was 17. It also burned so much oil that I had all my friends save theirs so I could run it. And it eventually maxed out at 45 downhill because it was so tired. Is it possible for the pickup screen part to fall off and the tube itself still attached? Mine seemed like that, as if the whole thing fell off, you'd imagine it'd suck air the whole time.
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
![]() |
![]() |
![]() |
#11 |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
|
Re: Factory oil pressure gauge fluctuates while braking
Here's a few pictures of my engine with the pick-up tube off. And one with the new engine I had to put in because it flat lobed the cam. You can see the difference and how the oil pump could cavitate if the pick-up fell off.
This one is not a real good picture of the pick-up. It sits right on the bottom of the oil pan so it's easy to see how it could cause the oil pump to cavitate if it fell off.
__________________
VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
![]() |
![]() |
![]() |
#12 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
|
Re: Factory oil pressure gauge fluctuates while braking
You're right, I visualized it wrong - without the pickup it'd still grab from the top of the sump, but likely grab air under slosh. I didn't think the pump went that far down, but I guess it does!
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
![]() |
![]() |
![]() |
#13 |
Registered User
Join Date: Apr 2016
Location: Santa Monica, CA
Posts: 18
|
Re: Factory oil pressure gauge fluctuates while braking
Thanks for the images guys. Before I drop the pan, where in the pressure sensor located? Do I have to yank this thing out to pull the pan or is it a motor-in-the-truck ordeal?
|
![]() |
![]() |
![]() |
#14 |
Registered User
![]() Join Date: May 2013
Location: WEST PALM FLORIDA
Posts: 1,174
|
Re: Factory oil pressure gauge fluctuates while braking
if it is off , put a tack weld on it , when you replace , so it does not happen again
__________________
68 Long Fleet , ly6 , turbo 350 , 3-5 drop , original paint , front discs 67 Small window , 7 foot bed , tweaked 6.0 LSX 2004R Medium Olive 58 Apache fleet , 235 , offy intake , dual exhaust , 4 on the floor , red/white 69 Long Fleet , Custom , 6.0, 4l60 , AC , Medium Olive |
![]() |
![]() |
![]() |
#15 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
|
Re: Factory oil pressure gauge fluctuates while braking
I think he said he's got a big-block, in which case those are down by the oil filter, but it shouldn't matter.
I was always paranoid about tacking the pickup tube on because I'd heard that heat could ruin the spring. So I'd take them apart first... and I also brazed them for some reason rather than welding (dissimilar metals maybe?) I have no idea if a little tack welding would really hurt the spring inside, but it can't hurt to take it out. Unless you forget to put it back in I suppose! Anyone know if you can drop the pan in a truck with a big block simply by raising the motor? I've never tried. I do know my grandfather did new rings and bearings in his '63 Biscayne without pulling the motor. He was a heavy duty diesel mechanic and I guess you get used to working in place, but I thought it was kind of cool. How he compressed the rings to get them up into the bores I really don't know... Pretty sure that would have been a 6 though.
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
![]() |
![]() |
![]() |
#16 | |
The Older Generation
![]() ![]() ![]() Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,524
|
Re: Factory oil pressure gauge fluctuates while braking
Quote:
(I modified my previous post on the port) LockDoc
__________________
Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - |
|
![]() |
![]() |
![]() |
#17 |
Registered User
Join Date: Apr 2016
Location: Santa Monica, CA
Posts: 18
|
Re: Factory oil pressure gauge fluctuates while braking
Well, my flex plate shattered and my bellhousing snapped a few ears off so im busy replacing that but I will drop the pan once I get the trans back in.
Rear sump, stock capacity pan, BBC- LOOKS like I can drop the pan pretty easy.... thoughts? |
![]() |
![]() |
![]() |
#18 |
Registered User
Join Date: Apr 2016
Location: Santa Monica, CA
Posts: 18
|
Re: Factory oil pressure gauge fluctuates while braking
TTT ttt
|
![]() |
![]() |
![]() |
#19 |
Senior Member
![]() Join Date: Jul 2015
Location: Warrenton VA
Posts: 1,053
|
Re: Factory oil pressure gauge fluctuates while braking
give it a whirl. you should be able to drop it enough to at least check to see if that's the problem. probably see in their easier too with the trans and flex plate out of your way as well.
__________________
71 c-10 Long Bed, under the knife for a No Limit Engineering Wide Ride Chassis Pack and coil over static drop. 07 Silverado Classic 2wd 95 Camaro 427SBC/TH350 |
![]() |
![]() |
![]() |
#20 |
Senior Member
![]() Join Date: Nov 2014
Location: Colorado
Posts: 3,225
|
Re: Factory oil pressure gauge fluctuates while braking
What about air in the line to the gauge? Its easy enough to have the engine running and just crack the nut on the back of the gauge and let a little oil out until you get a steady reading on the gauge.
__________________
07' Extcab Silverado Z71 Silver Birch, 5.3L HO 71' Cheyenne C10 Hugger Orange on Saddle SWB Besides these two, too Many to count |
![]() |
![]() |
![]() |
#21 |
Senior Member
![]() Join Date: Jul 2015
Location: Warrenton VA
Posts: 1,053
|
Re: Factory oil pressure gauge fluctuates while braking
only reason it should have air in the feed line is if it's super low on oil, or sucking air at the pick up.
__________________
71 c-10 Long Bed, under the knife for a No Limit Engineering Wide Ride Chassis Pack and coil over static drop. 07 Silverado Classic 2wd 95 Camaro 427SBC/TH350 |
![]() |
![]() |
![]() |
Bookmarks |
|
|