I believe my oil pump on my 1991 Aerostar AWD, has failed. The oil pressure fluxuates (electronic dash, oil warning buzzer goes off). I have some lifter noise but no knocking. I am seeking replacement advise. Is it possible to drop the oil pan and change out the pump with the engine still in the van? Or is it necessary to remove the engine. And, if so what is the best proceedure? Thanks for any and all advice.

 

I have a 93 4.0 AWD. It looks like you probaly have to pull the engine to get the oil pan off. How many miles do you have? I would test the oil pressure with a good gauage. Hopefully it is a bad instrument gauage. Than go from there.Most times a new oil pump does not fix low oil pressure, usually for high mileage it is worn crank shaft bearings.That means, engine rebuild or van trade.

 

Thanks for the reply. Tonight I changed the oil, and started the engine, and low and behold oil pressure went to the top bar on the gauge??? Go figure! Best I can figure is that I have some gunk in the pan and it blocked the screen or the pick up tube or? (something). I let it run at idle for over an hour and the pressure stayed right up there. Anyone else have a similar experience?

 

[updated:LAST EDITED ON 10-Oct-02 AT 04:03 PM (EST)]A key finding here is: Did the lifter rattle also go away when you changed oil and the pressure gauge began operating again? If so, then you did have an obstruction some where in the system. If you changed the filter along with the oil, there is a strong chance the old filter may have collapsed internally and impeded oil flow. Any further details you could provide would be helpful for future reference.

 

Well, I am sad to report that the fix did NOT last. I took the van out on the road today and after a bit the pressure dropped again down to one bar (digital dash) and the alarm went off. I'm confused. Any further help would be greatly appreciated.

 

Hi. First, a clarification. I've owned several Aerostars, including a '91 AWD with digital dash like yours. What looks like an oil pressure gauge is, in fact, not. The sensor on the engine is simply an on/off switch that is set to about 4psi. When the pressure is over that, the "gauge" indicates "high". When below that, it lights a single bar and sets off the dash alarm. Rediculous, isn't it? Ford does this on many of their cars/trucks. My present '96 Aero and my '99 F150 both have "gauges" that aren't. Guess it saves them 50 cents per car...
Now, as to your problem... the only way to be sure is to remove the oil pressure sensor and put a gauge there temporarily to see what is happening. Given your description, the probability of a bad pump is pretty low. Most likely its the sensor (less than 10 bucks at Autozone) or the connection/wire to the sensor.
Post here and let us know how it turns out.
KenP

 

I have the digital dash on my '87 Aerostar XLT, and have experienced the EXACT same dilemma as you. In fact, I swore I would never own anything with a digital dashboard again! I can almost assure you, it's NOT the oil pump, unless the engine is badly worn, with blow-by in the cylinders, piston slap, and hazy light blue oil smoke coming out of the exhaust. Otherwise, it's probably the sending sensor that goes into the oil pan (for lack of a better term) It was an intermittnet problem when it first started. When driving, suddenly the oil pressure guage would come on, at one bar, with the flashing oil symbol. That warning tone about drove me crazy. I knew instantly it had to be an electrical problem, because the oil pressure guage was either 4 bars (normal) or one bar (warning) There was never any other variation to this. At first it started slowly, drop to one bar (tone sounding) and instantly go to normal. Some days, no one bar warning at all. Eventually, it started to happen more frequently, usually at the worst time (going to dinner on a friday evening) and the annoying warning tone, again, was horribly distracting. One Saturday morning, I pulled the Aerostar up on some car ramps, engine idling and hot. With the oil guage at "one bar" and beeping, I crawled under the van. With an observer sitting in the drivers seat, I gently touched the sensor wire going into the oil pan. Instantly, the guage went to 4 bars (normal). I knew it had to be that. About a week later, a mechanic friend checked the oil pressure with a independent guage, and he said it was normal, hot, at idle when the digital dash showed one bar. Anyway, he replaced the wire and sensor (also had to remove the interior engine access panel) Unfortunately, I had to get the parts from the Ford dealership, parts dept. Either my nearby Autozone, NAPA, Kragen etc. didn't stock it, or the clerk was too stupid to understand what I needed, I'm not sure. Anyway, I currently have 4 1/2 quarts of 10W30 Mobil 1 with SuperSyn, and a Motorcraft FL400S oil filter, the van runs perfect, and no more problems. Hope this long-winded true story helps! Ed...

 

Sensor in the oil pan is an oil LEVEL sensor... it sets off an alarm if the oil level drops too low... it is not connected electrically to the oil "pressure" indicator and has nothing to do with oil pressure. Its nothing more than a "float".
If your mechanic removed the inside engine cover, you must have a 3.0 V6. The pressure sensor for the 3.0 is located on the back of the engine and is accessed through this cover. When my dash indicator started going nuts, this sender was the problem.
On the 4.0 the pressure sensor is located on the left front of the engine.
KenP

 

KenP, thanks, you are completely correct. Here I thought he the wire going into the oil pan was the problem. Yes, this was replaced too, on my van. On a whim, tonight, I took off the interior access panel, shined a bright flashlight onto the rear of the engine, and sure enough, the oil sending part, still looks as a brand new replacement item. Unfortunately, I don't have my service invoice handy to check the part number. Thanks for posting, again, you are correct and I am glad I don't have that annoying problem anymore. Is this an isolated thing with the digital dash, or I wonder if it happens with the Aerostar's standard dash guages as well? Thanks Ken ... ED

 

Ed, you're a better man than I if you're willing to take off your access cover "on a whim"...
On my Aero, getting that cover off is a major pain... gotta remove that dumb cup holder thing on the floor and remove the ABS module from under the dash just to get the pleasure of contorting my old body to reach the clips... who thought that up????
Anyway, problem is not isolated to digital dashes... sensor is nothing more than an on/off switch and is used in almost all Fords... regardless of dash configuration.
I think its an awful scam that Ford puts "gauges" on the dash that really aren't. Everybody thinks they are looking at oil pressure, when they're really not. A real oil pressure gauge goes up and down due to oil viscosity (temp) at idle, etc. Fords don't. It just sits there pointing at the same pressure all the time... dumb.
Wonder how many folks have bought a used Ford and thought the engine was in great shape because the oil pressure was "just like new"???
KenP

 

Hi Ken ... Yes the interior access panel is easy to remove. I have one of the early Aerostars (1987) with the transmission shifter on the floor, instead of the newer vans which is on the column. I find if I move the gear selector to "D" or lower, it gets the gearshift out of the way from the cover. Then, simply remove the clips, and it's done. Those early Aerostars don't have any cup holders, even with the XLT trim. I'd like to get a new Aerostar, say around a '95-'97, but this van, besides some annoying "quirks" here and there has been very reliable. It is in excellent shape, being in the garage every night, and when not in use has helped. Living in California, the van has no rust what-so-ever, in fact I can still see remains of factory markings, and paint checks, on the under carriage from when the van was new. I like RWD too, maybe if I lived in the snow belt, I would rather have the traction, handling in a FWD van (Windstar, Caravan, etc.) but for the time being, this old stud van will suffice, no monthly van payment is a plus too! Ed
PS "New" Aerostar, I should have written, getting a "newer" Aerostar

 

I have a 1989 Aearostar and I changed the oil pump / pick up screen with out pulling the engine. I am not the most mechanically inclined individual by far, but with a Haynes manual and some persistance it can be done.

Brian.

 

I own a 89 Mecury Cougar with digital Dash. I recently started hearing te warning tone and just now noticed that when the tone goes off, the oil guage drops, then a few seconds later goes back to normal and the tone stops.
It only happens occasionally. I am not great with cars and wonder what my next step should be? Take it to a dealer? Any help would be great. Sounds like I am having the same "ford" related problem described in this forum.


>I have the digital dash on my '87 Aerostar XLT, and have
>experienced the EXACT same dilemma as you. In fact, I swore
>I would never own anything with a digital dashboard again! I
>can almost assure you, it's NOT the oil pump, unless the
>engine is badly worn, with blow-by in the cylinders, piston
>slap, and hazy light blue oil smoke coming out of the
>exhaust. Otherwise, it's probably the sending sensor that
>goes into the oil pan (for lack of a better term) It was an
>intermittnet problem when it first started. When driving,
>suddenly the oil pressure guage would come on, at one bar,
>with the flashing oil symbol. That warning tone about drove
>me crazy. I knew instantly it had to be an electrical
>problem, because the oil pressure guage was either 4 bars
>(normal) or one bar (warning) There was never any other
>variation to this. At first it started slowly, drop to one
>bar (tone sounding) and instantly go to normal. Some days,
>no one bar warning at all. Eventually, it started to happen
>more frequently, usually at the worst time (going to dinner
>on a friday evening) and the annoying warning tone, again,
>was horribly distracting. One Saturday morning, I pulled the
>Aerostar up on some car ramps, engine idling and hot. With
>the oil guage at "one bar" and beeping, I crawled under the
>van. With an observer sitting in the drivers seat, I gently
>touched the sensor wire going into the oil pan. Instantly,
>the guage went to 4 bars (normal). I knew it had to be that.
>About a week later, a mechanic friend checked the oil
>pressure with a independent guage, and he said it was
>normal, hot, at idle when the digital dash showed one bar.
>Anyway, he replaced the wire and sensor (also had to remove
>the interior engine access panel) Unfortunately, I had to
>get the parts from the Ford dealership, parts dept. Either
>my nearby Autozone, NAPA, Kragen etc. didn't stock it, or
>the clerk was too stupid to understand what I needed, I'm
>not sure. Anyway, I currently have 4 1/2 quarts of 10W30
>Mobil 1 with SuperSyn, and a Motorcraft FL400S oil filter,
>the van runs perfect, and no more problems. Hope this
>long-winded true story helps! Ed...
:-X23