My engine rattles for about 2 seconds whenever I start it. (it's not oil filter drainback) Oil pressure is just fine once it's running.

Do all the I - 6 engines do this ?

I am considering putting a canton oil accumulator on for preoiling,
as my only issue is the rattle upon startup.

I would pull the pan and put in a new oil pump along with new rod and main bearings............ but I really don't like crawling around on the ground and getting covered with oil. Putting on the oil accumulator looks ALOT easier than pump, rods and mains.

So what should I do ?

!) leave it, and ignore the rattle

2) oil accumulator

3) Oil pump/ rod & main bearings

 

What is the year and mileage on the engine?
How do you know it is not the anti-drainback valve?
Do you have an accurate oil pressure gauge with numbers on it?

No, but with cheap oil filters I have heard they will. Recommend the Motorcraft FL1A filter.

IMHO this is a wonderful device, but is overkill, expensive, and creates a new source for leaks/problems.

Not sure you need all this. You said oil pressure is good. I suggest a quality pressure gauge, say Autometer. Map the oil pressure:

Get engine hot (minimum 15 miles driving) until oil pressure stabilizes, then record the oil pressure at 3 or 4 hundred rpm intervals (need good tach like my Datcon 0-4000 from JCWhitney) from idle to maybe 2500 rpm. Graph results. Draw straight line from idle to 2500 rpm pressure. All intermediate pressure readings should be above that line in a nice curve. I they fall under the line or are close, you may have problems.

* Try a Motorcraft filter
* Get other's advice off this board
* Get real oil pressure readings. Main bearing slop will show in low pressure throughout the rpm range, whereas rod big ends will sling oil more under RPM and so pressure should drop with increased rpm. Spec is 40-60 psi at 2000 rpm hot.
* Be sure you are not using too thin an oil (5w30 not so great). I run 10w40 in my 300 (107,000 miles) and get 45 psi hot at 2000 (5w30 got me only 36, but no startup knock)
* Check if oil pump pickup screen is sludged clogged
* If main bearings are loose, suggest thicker oil. Don't spend a couple hundred on accumulator for worn out engine.

DON'T do anything expensive until you post more data and get much more advice.


EDIT: You also could get startup rattle on cold starts if too thick an oil (say 20w50) in sub freezing weather. Or if your oil is degraded--i.e., past needing to be changed-- you could get a startup rattle.

 

Thanks very much for the detailed reply.

I thought it was oil filter drainback at first, so I have already tried several different filters, and I have an FL1A on it now and it still does it.

I am going to install a mechanical oil pressure guage when the rain stops sometime this week. I will also change to a thicker oil.

( 5-30wt synthetic in it now)

Hopefully I can get this rattle to stop without having to break open the bottom end of the motor, wrenching underneath trucks is not my favorite thing to do......... I know how, have all the tools, and knowledge.......... but would rather not spend my day off doing it.

Truck runs absolutley perfect aside from the rattle.

1992, M5OD, 2.73 axle
185,000 miles

 

I am not that knowledgable on synthetic oil. It does flow quite well, pretty slippery. Perhaps it is seeping past antidrainback, but sounds like something else. The oil pressure gauge should help narrow things down a lot. I really like my Autogauge (by autometer) with its 2 psi increments. 186,000 is not a lot of miles for this engine. My '84 has 200,000 on it. When i sold it it had 175K and ran great! Wonder if you could pull the drain plug and then pour hot motor flush down the oil pump exit hole (between the filter mount stud and gasket flange. Maybe that would wash off the pickup screen and run the scum out the drain hole. I just made this up, but who knows--might work. If you do, though, you will have to prime the pump by running copious quantities of oil down the same hole. Wouldn't do it with pressure or air hose as could damage pump gears. Just pouring and hope. I'm just rambling, thinking out loud. Hope you solve it quickly and simply. let us know the final result. But give it this evening and surely others will be posting tips. Maybe the oil and lube forum would be helpful. I think you can post in two forums at once.

 

One possibility.

It could be your cam gears.
When you start, your cam gears are dry, and they will rattle till oil gets to them. Listen at idle, there may be some rattles that come and go.

Your truck has the Phenolic Resin gearset, and with 185,000 mi, I'd suggest replacing them with a steel set. Just some cheap insurance.

High mileage wear will eventually cause the cam gear to fracture.
A Rather unpleasent surprize.

Go with a higher weight oil too.

 

My chebbie used to have lifter knock on startup, is used wix filters and mobil 5w-30 semi syn oil. It would do this no matter what. I read a post on here about marvels mystery oil cleaning the internals of a motor oil. MMO is not snake oil by any extent. I changed the oil in my chev at 3000 miles with a filter, and replaced on of the quarts of oil with MMO, and then changed it a thousand miles later. After about a 100 miles on the oil, the knocking stopped, i got about 5 more psi of oil pressure accross the board (the motor only has 40k on it). I would try using it, i have never used a better product before. It does what it claims. I did not imagine that my oil would be that dirty when it came out at a 1000 miles, plus now my oil stays a lot cleaner.

 

The truck was a recent purchase, and the previous owner was seriously lacking in the maintainence department. He owned the truck for about 4yrs and put 60,000 miles on it. I seriously doubt he changed the oil during that time.

The first thing I did was to put on a new filter and top it off with a quart of MMO. I love that stuff. It works great for cleaning out old engines. I drove it that way for a couple days and then changed the oil and filter.

It started to rattle upon startup right when I changed to the 5-30 synthetic. So I changed the oil filter to a FL1 thinking oil filter drainback was the problem....... but the rattle continued.

Today I drained the oil and put in some Delo 15-40 that I had left over from my powerstroke desiel.

I think the problem is solved. I can still hear a slight rattle when starting, but I mean slight. If I wasn't intentionally listening for it, I would not notice it. It's nothing like it was before, it sounded like a desiel starting with the 5-30 synthetic.

I might still throw a mechanical oil pressure guage on it to check the pressure. I read somewhere that our pressure guage is operated just by an on/off pressure switch that is set to about 6psi, which means the oil pressure will read just fine on the factory guage even if you only have 6psi of pressure.

 

Glad to hear you got her straightened out--more or less.

The stock "gauge" is sham. You can see the sender is about 1 by 1 inch with a tip, whereas I am told the real gauge has a sender more like 1.5 " and somewhat conical. My '90 E350 had the real looking sender, but the gauge acted dummy so I installed mech gauge. I like the mech gauge.

Some try to scare with the popped line stories, but if you do the install right should be OK. I shrouded my line in the E350 cab with clear plastic tubing from the hardware hose clamped to the compression nut. If the line should come loose the oil squirts on the floor, not in face. . But in my F150 no shroud. Take my chances. Wife and kids don't ride in it.

Good discussion anyway. See ya later.