You guys helped me out a while back in finding the sending unit on my '77 with a 460. Now I got another question.

When I start my truck in the morning, the pressure runs up to just below the "HIGH" normal line, and stays there until it gets warmed up.... As it warms up it gradually drifts down....Once it is fully warmed up and "hot" the needle is between the "O" and the "I" in OIL. HOWEVER, when I am stopped at a light......it goes all the way down to ZERO, but I do not get any unusual noise that I would expect to hear if there was no oil pressure, nor is there any degradation in the performance of the motor. It has an automatic transmission, and if I pop it into neutral or park, it will usually come up to at least the L if not back into the normal range.....I don't think the motor is idling too low, and it runs extremely smooth, sounds normal, doesn't miss any, doesn't have any oil leaks....

The sending unit is of course new, the temp gauge is old, probably original....I am thinking about buying an aftermarket guage with actual numbers on it to see what I get.....

Anybody else experienced this? I am really not in a position to go rebuilding the bottom end (the heads have been replaced)....suggestions?? Ideas??


BTW I am running 5w30 or 10w30 (I can't remember which oil I put in, but it is only about a month old)and the air temps are in the 20's to 30's in the AM and 40-50's in the afternoon where I live

thanks in advance.

 

Hi:
Mine '78 F150 with 351M, does about the same thing in the morning, except mine goes a little further than 3/4 of the way up in the normal range, then after about 5 minutes settles back down and stays in the middle of the normal range, unless I'm idling for a while at which time it drops a bit.
I don't blow any smoke on start-up, doesn't smoke while driving and I have not noticed any leaks.
I just changed the PCV this past weekend, no oil sludge there, and I haven't noticed any blow-by at the dip stick or valve covers.
There are several other posts on the forum that address this issue.

Have Fun.
Dave
'78 F150

 

First,you have to consider the mileage of the engine.

Because of the fact is goes up when first started, that shows due to the contraction of the oil bearings on the Crankshaft and Camshaft from being cold.
Once they warm up they expand allowing a larger gap, lowering the oil pressure.
With the engine at idle is would show even less.

Then other reason could be the wearing of the oil pump.

One thing you can try is use 20-50w oil.
Or find a straight 30 weight oil to put in it.

Installing a mechanical oil pressure gauge is a great idea to monitor the ACTUAL pressure.
It can be run from a T-Connector at the sending unit.

Dennis



Please Don't Ask Me Any Tough Questions As:
"I'm Saving My Memory For When I Develop Alzheimer's"


78 F-150 429CJ,Silver
w/Explorer Pkge.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon

 

aaah, one of the posts reminds me....it does not burn or otherwise comsume oil, the exhaust pipes are not sludged with oil residue, and other than a barely detectable puff of smoke when it is started (which I think is from the rich mixture on start up...it smells rich), it does not smoke AT ALL.....


AS for the 20w50.....I have always been told that V-8's get nothing heavier than 30 weight.....PERIOD....can anybody help with that one?

Will replacing the oil pump be a cheaper alternative? How big a job is it? For frame of reference, so far, the biggest job I have done on this truck is radius arm bushings....which started out pretty ugly until I talked my wife into letting me get an air compressor and impact wrench... So how would replacing an oil pump compare to that?

 

Ack,
If you can talk your wife into changing the pump, this could go very smoothly for you, or not?
Your puff of smoke, at start up, is one of two things.
1. Black Smoke, Fuel; Rich Choke setting.
2. Bleuish Smoke, Oil; Valve seals.
The pump is a nightmare to change. I would wait until I here lifter ticking. Then buy a high volume oil pump, not a high pressure oil pump. I ran a 302 for 8 years with identical syptoms and have no problem till this day. I run 20/50W oil with no repercussions. Your truck will run its lowest pressure right after an oil change. Check it and see if I speak the truth. Once the oil filter gets gummed up it will read higher.
Pressure is read prefilter and guarantees nothing after that.
My Way is the Highway
KingFisher

 

i was told that for 351-400M and 460's run 10w40. thats what i run in my 400 and i have had no problems

 

ackusackus, I have the SOLUTION. Use STP and strait 30 weight oil in your engine -trust me. I know you are all thinking what'll that help, but it's true, STP works. When the oil pressure drops low, the STP will stay on the bearings, lifters and keep them lubricated even if the oil pump temporarily has no pressure at all.
I have a friend with a 360 where the oil pump wouldn't pick up for about 6 seconds after he started it. After rebuilding the engine from oil starvation, he had the same problem, so he dumped some STP in it. It's still running strong and the oil pump still doesn't pick up for about 6 seconds. THE STP will protect the engine untill the oil pump picks up. I've seen how good STP works.
I have almost no oil pressure in my 78 351m and STP keeps it runni'n like a champ.

 

Changing the oil pump on your truck can't be done with the engine in the truck. There is only about an inch of clearance between the bottom of the pan and the crossmember and I don't think you can lift the motor high enough while it is bolted to the tranny to get the pan off. The bearings could be worn also. Had this problem with the 460 I put in my 79 4x4. I didn't install new bearings before dropping the motor in and 2 months later, I was laying on my back under the truck replacing the main bearings.

 

I live in the desert southwest where summer temperatures can reach 112 deg F. After driving for a short period of time my oil pressure will take a drastic drop. Stopping for a red light will often make the pressure gauge bottom out. I keep my cooling system in good condition and there was no abnormal rise in operating temperature or signs of an overheated engine. I tried the STP bit and it did not solve the low oil pressure problem. Next, I went to 20-50W oil which did not make a great difference once the engine was warmed up. I am afraid that the pressure gauge will still bottom out when summer returns. Other forum members have told me they have the same problem and have learned to just live with it. I think installing a manual gauge could relieve some of the worries. The sender on my 78 F-150 is a Bear to get too. I am thinking that a plumbers faucet wrench (used to remove the water supply lines under the kitchen sink) may be a handy device to remove the sender with. Any thoughts on that brainstorm???

 

Vice grips,Channel lock pliers(as you mentioned)

I suggested a mechanical gauge plumbed in a T-Fitting at the sending unit.
Also, check for a plugged orifice when you remove the S.U.



Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg



Please Don't Ask Me Any Tough Questions As:
"I'm Saving My Memory For When I Develop Alzheimer's"


78 F-150 429CJ,Silver
w/Explorer Pkge.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon

 

I had the same problem on my 79 400.Talked to ford they said it is a typical problem with these motors.They said that 7-10 psi after warmup is normal. Not being a very trusting soul i installed a aftermarket oil pressure gauge just for safty sake.I also run the 20w 50 oil. On start up i get 60 psi and after it warms up 15psi idle and about 20-25 running down the highway no mater what the temp outside.If you are really worried about it then the high volume low pressure oil pump can be installed without removing the engine Ive done it on my old engine but it is a pain just make sure u get the pan gasket in properly but u will probably get about the same oil pressure readings. It didnt change mine much. Hope this helps.












Six strings and Ford trucks music to my ears.

 

thanks to all the info....I am a little touchy about oil pressure as I smoked a motor on a previous vehicle due to oil problems....it had an idiot light, and I accidently knocked the wire loose on the sending unit....Luckily, that was a bug....very easy and cheap motor to replace....


I think I'll go with the aftermarket pressure gauge, the different weight, and throw the STP in for grins and giggles (since the jury is split on it)...one other question...can they run off my existing sending unit or do I need to get one specifice to the brand of gauge?

thanks again

 

A Mechanical Gauge is one that has a tube that oil flows through up to and into the gauge inside the cab,mountedunder the dash.
Positive pressure actuated.

An electrical gauge is one that works like the one you have.

I mentioned installing a T-Line that attaches where the sending unit comes out with Both of the systems working.

This gives you a comparison from two gauges.

Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg



Please Don't Ask Me Any Tough Questions As:
"I'm Saving My Memory For When I Develop Alzheimer's"


78 F-150 429CJ,Silver
w/Explorer Pkge.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon

 

Yes, try NAPA auto for a T fitting for oil gauges. I'm sure you can get mechanical guages from there.
And for the STP, no it will not show any difference on your guage, It's the bottom end that shows the difference. I been there-I seen the difference.:-)

-Dan