2ed opinion

[Rocknrotty]

Looking for a second opinion

Resurrected this Bronco last week and have several minor problems still to work on but this one is a little worrisome

At startup oil pressure is good middle of NORMAL

when warm oil pressure drops so as to not register at all

Since the motor has not seized yet i am assuming that the oil pressure is ok

(maybe low) and that the pressure sensor is kaput

any opinion's ???

tks

-R

 

[Krafty]

the oil pressure sensor on your 351 will be an acorn looking thing behind the power steering pump on the drivers side of the block between the timing chain cover and the cylender heads, it'll have a single wire going to the connector on the top of it, it will either go right in to the block or have an extender on it that takes it a few inches away from the block. put a wrench on the base and thread it out. then thread on the new one and connect the wire and your done.

 

[Rocknrotty]

So you believe that the sensor is fried

-R-

PS. I know where the sensor is and how to replace it but just looking for opinion's if this is the problem

as someone has on there signature here "Replacing parts is not troubleshooting"

thanks for the reply

-R-

 

[Seabronc]

The sensors have a reputation of going bad. Has you engine been rebuilt or is it the original. As the engine gets older and wears the ability to hold pressure decreases. There are numerous thing that could be wrong or even a combination of things. Some possibilities are: sender, engine wear, oil pump, cheap oil filters, etc. If it is engine wear you can put off the inevitable rebuild or replacement by increasing the oil viscosity. In the Summer I use 20W50 in the Winter 10W40, both of them along with a quart or two of Lukas. I always use Baldwin filters, a common filter used on heavy equipment. A Mobile 1 filter is also a good one. A cheap filter will often go into bypass and lower the pressure to 0.

I'd recommend you get yourself a wet pressure gauge that reads in pounds instead of the Ford gauge which doesn't provide much more help than an idiot light. As a rule of thumb 10 pounds of pressure per 1000 RPM is plenty though mine is higher than that at cruise. I would have rebuilt mine by now, but it runs strong with only the weak oil indication issue.

Good luck,

>-

 

[Seabronc]

Re: the parts replacement is not trouble shooting.

This is not an easy one that lends itself to troubleshooting down to the most likely part. You can possibly borrow a wet pressure gauge and hook it up in place of the sender unit and see what it tells you. If it agrees with the Ford gauge then you need to do some analysis of the situation like how long has this engine been running since new or rebuild and how was it treated in that time period.

You know you have to change oil, then put in a good grade high viscosity oil, and use a high quality oil filter. as far as the oil goes, a lot depends on where you live and what ht outside temperatures at this time of year are. We don't normally have temperatures down in the 0 to -0 F range like we have had in the past few days. Usually we have temperatures in the range of mid 20s F to mid 30 which is OK even if I leave 20W50 in my engine but it is on the edge and makes starting a little harder. 10W40 which is what I have in it now is on that edge now that we have been in the 10 to 20 F range for about two weeks. If you are in an area above the low 20s, I'd use 10W40 plus Lukas up to the 80s F. Above that I'd recommend 20W50 plus Lukas. However, oil and the temperature is the kind of thing you need to play with to see what works for your particular engine. That might take you an oil change or two, it is more slanted toward the art side of this thing rather than the science side like the statement at the bottom of my signature.

If it is a new engine then find out why and go for the exact component that is causing the problem, but if it is an old tired one or even an old but running great one try some of the things I mentioned above. That is not all inclusive or everything you could or should do, just a quick comment.

Good luck,

 

[Krafty]

What I was getting at was to swap the sensor to rule out any other serious issues. how long has it been sitting? did it have this problem when you put it away? and what are you other issues? they somehow be related if there is indeed a serious issue.

 

[Rocknrotty]

Thank you very much for your very informative answers

this motor has 164000 KM or about 101000 mi. but it is 28 years old

It sat for about 13-14 years starting every 6 months or so run up and down my drive way (long drive way) in 4x4 just to stir oils up

I am using Castrol 10W30 with a Fram filter

Temperatures here have been very cold but last 3 days very mild 32F-40F

When hot and RPM's are over 2500 oil pressure is good middle of normal

at idle 800 RPM oil pressure is not registering

When cold at idle oil pressure is showing middle of normal

So I will go buy a REAL oil pressure gauge and check it

Sure hope it is just the sending unit mind you these things have sooo much room under them

that changing the pump should not be too hard at least i can see all oil pan bolts

and for the next month while my neighbor is in Arizona I get to use his hoist

Thanks again

-R-

PS to Krafty I read through my last post and it comes off as a little sarcastic sorry about that my bad

 

[miesk5]

yo; great advice as usual!

Look @ da oil pressure sender's diaphragm when you pull it; they bust a move; could be temp related...cold = ok; hot = opens up - let us know what it looks like

GL!