i have this problem with my 93 w250: when i start it cold the oil pressure quicky reaches normal operating range, but as she runs and warms up, her oil pressure slowly begins to fall. i don't know how far it will go as i shut her down before she drops out of the gauge. (yes dear, the oil level is fine)

i had the oil pressure checked to make sure it wasn't the gauge or sending unit or something like that, the oil pressure is doing what the gauge says its doing.

my usual mechanic says that that is not symptomatic of a bad oil pump and the only other thing it might be is the main bearings. a call to another diesel shop suggested that it might be as simple as a bad filter, otherwise it is the oil pump or main bearings (both requiring that the engine be pulled, very $$$).

the truck has only about 155K miles on it, and so i can't imagine that it is the main bearings. it runs fine as well. it starts easy. it doesn't smoke.

any and all suggestions (especially the cheap ones) are welcome.

thanks.


laura

 

What brand of oil filter?

Please don't say it's a Fram. :
From expereince I had a 318 gasser doing the same thing because of a Fram filter.
If so....Heave it and get a real Oil Filter, Fleetguard, Baldwin, Wix, ....one of the GOOD ones.
Frams and CTDs don't mix.


edit: Welcome Laura 8)
..."Noobie" whadda title...... ..We wuz ALL Noobies once.

 

Agreed could be the filter, especially if it is a cheap one. They have been known to ruin these cummins engines.<br><br> Oh and welcome to the site!!

 

i believe that the filter is a fram [undecided] <br><br>the replacement filter i bought was a napa gold. are these any good? <br><br>thanks<br><br><br>laura

 

Was the oil changed recently?
If so, did this start not long after the change?
Sorry for all the questions. [undecided]

In my opinion a roll of cheap toilet tissue is better than a Fram.
I'd try swapping the oil filter first, then try a little test drive.

Hope this helps.

 

It could be the pressure switch/sender for the gauge. I have an old 84 f350 with the 6.9 diesel. When I bought it the oil pressure would appear to drop. I replaced the pressure switch/sender the problem went away. <br><br><br>

 

In your first post you stated that the pressure was checked with another guage and that also showed a drop in pressure.<br>If the second test guage was a mechanical one, I think that would eliminate the sending unit as a possible trouble.<br><br>I'm still leaning toward the oil filter as the culprit.<br><br> ???

 

as mentioned in my first post, its not the sending unit or switch. they are both working properly.<br><br>the oil hasn't been changed recently (maybe 2500 miles ago) but i did start noticing it recently and haven't driven it at all since i noticed.<br><br>i checked and the filter on it is indeed a fram. i'll change it tomorrow (with a napa gold which is the same as fleetguard, i think). <br><br>thanks again<br><br><br>laura

 

Laura, there has been some problems in past with the Fram filters breaking down internally. A small filter particle would escape the filter and end up blocking a piston oil cooling nozzle. The good part from what I've read is that Fram has backed their product and paid for engine damage. My understanding, is that Fram and some other makers were using some sort of neoprene within the filter. This was separating and causing the problem. <br><br>I would contact Fram and put them on notice of the pressure problem and that it may be filter related. Your mechanic could varify your oil pressure up to this filter if you've been using the same mechanic. Strongly suggest that you make a record of your situation to date using date of incident, person doing your pressure tests, etc.. Brief your mechanic on your plan and have him also clean outside of filter before removing. Save the filter and protect it. Pour the oil into a suitable container and also keep it. I would also devise a sealing method with box or some container that could be taped sealed and have the seal dated and witnessed with signatures. <br><br>No harm done if a new filter takes care of the problem and all is ok after ample time and driving. However, you will be in a better position to support and prove your claim if you have an internal problem now or later caused from this filter.<br><br>I'm not trying to scare you. Just want you to protect yourself some by saving and protecting the evidence. <br><br>Fram is made by Allied Signal if my memory is still intact.<br><br>Good luck ...<br><br>Jerry

 

i've documented everything thus far (oil pressure being the last and most serious problem i've had so far).<br><br>based on the way the problem is manifesting, and on the oil pressure threads i've read over at the TDR, my suspicion is that the filter is colapsing on itself internally, rather than breaking up and sending particles into my engine.<br><br>but everything is documented nonetheless. thanks.<br><br><br>laura

 

Laura, I can't consider myself an even a novice mechanic. That said, let me tell you about a situation I have with my 5.7l in my '89 gas pickup. The engine has 146,000 miles and I've treated it well since I bought it new. However, when the engine reaches running temperature, the oil pressure, at idle drops, at times triggering the &quot;Check Guages&quot; light. My mechanic has told me this, and I not knowing any better, have to go on his word. He's figuring that the main bearings are worn regardless of excellent care I gave it, causing an excessive amount of oil to get around the bearing surfaces. At idle, and when hot and the oil is less viscous, the oil pump can't keep the pressure up. Interestingly, I notice that this problem is exacerbated by using synthetic oil.

You didn't indicate if you've had this truck since new, but if you didn't, it's very possible that the previous owner might have caused premature wear by poor maintenance. Just a guess.

 

I guess another question would be oil type and viscosity? I would hope its 15W40 or at least a W-40 blend. I noticed a drop on my 89 with 0W-30 oil, used alot more too.

If the filter has plugged anything, the pressure should go up a tad.

Does anyone know if there is an oil pressure relief valve built into the engine? Most industrial engines have them. Maybe that part has gone haywire?

Some thoughts..

J-eh

 

I'd go for an oil change incluuding filter first. Use the oil that is suggested in the manual. Keeping the evidence is a good idea. <br>Maybe it's just the bypass in the filter that's causing the problem. <br><br>Good luck, I hope it turns out to be something minor<br><br>AlpineRAM

 

As per my 96 service manual, there is a pressure regulating valve that will open and drain partial oil flow to oil pan if pressure exceeds 65 psi. This could cause pressure problems if it is malfunctioning and may be the problem. Is pressure quickly building to 55-65 and then just falling off? If so, this may be the regulating valve going into drain off mode. <br><br>There is also a filter by-pass valve that is suppose to open and by-pass the filter if it becomes blocked. The valve is designed to open when there is a drop greater than 20 psi across the filter and will allow unfiltered oil to flow through the engine. With this being the case, it appears that pressure could be maintained even if the filter was completely plugged.<br><br>Anyway, I guess it is trying a new oil filter and going from there. Let us know what you find.<br><br>Jerry

 

tried the oil and filter change (napa gold 1607, delo 400) and no change. <br><br>i noticed something before, but had forgotten about it; under load, the oil pressure, once warm, stays in the normal range, but at idle the bottom falls out. is this indicative of anything in particular?<br><br>also, there was more white smoke than normal.<br><br>any ideas?<br><br>thanks for the help so far.<br><br><br>laura