Ford Mustang Forum banner

Status
Not open for further replies.
1 - 14 of 14 Posts

·
Registered
Joined
·
51 Posts
Discussion Starter #1
Hi fellow mustang owners!
I am in an urgent situation right now. This past weekend I changed my oil & filter and automatic transmission fluid and filter as well. I have been driving my car and all seemed fine, until this morning on my way to work.

The oil pressure gauge was constantly flinging back from completely Low (in the red) to slightly over half way towards the High pressure side, all this happening while driving. What is happening? How can I fix this? My stang is a 1999 V6. I just put in 5W-30 castrol gtx.

Thanks a bunch! I don't want my pony to die! :(
Tom
 

·
Registered
Joined
·
6,158 Posts
no oil leaks? you put 5 quarts in? maybe a crappy filter, what kind did you use?
 

·
Registered
Joined
·
51 Posts
Discussion Starter #3
i used castrol GTX 5W-30... 5qts of Oil. no leaks. the filter is a Purolator pureONE filter.
 

·
Registered
Joined
·
3,775 Posts
i don't think it will affect your pressure reading but aren't you suppose to use 5W-20 motor oil? thats what it says on the cap
 

·
Registered
Joined
·
51 Posts
Discussion Starter #5
its funny because in my manual it says 5W-30, and when I went to Advance Auto, they told me the system said 5W-20... I just said I'll go with what the book says.

i also noticed that when I turn my engine on and view the 'HEC Diagnostic Mode' (HEC Diagnostic Mode)... the Oil pressure is a constant 000 when running. It does not fluctuate at all. However, the oil pressure gauge shows the oil pressure in the middle.
 

·
Registered
Joined
·
3,775 Posts
its funny because in my manual it says 5W-30, and when I went to Advance Auto, they told me the system said 5W-20... I just said I'll go with what the book says.

i also noticed that when I turn my engine on and view the 'HEC Diagnostic Mode' (HEC Diagnostic Mode)... the Oil pressure is a constant 000 when running. It does not fluctuate at all. However, the oil pressure gauge shows the oil pressure in the middle.
huh, thats odd the book says that, what it say where you put the oil in at (on cap). the thing about the oil pressure, maybe the sensor needs to be replaced, if i read that thing right about the 0-176 then its reading 0 psi, but the cluster seems to think its reading normal, in that case it might be the cluster messing up in that one gauge, this is all speculation of course, find wmburns on here, he can most likly tell you what the cause is or at least will narrow it down to 2 or 3 things for you
 

·
Registered
Joined
·
51 Posts
Discussion Starter #7
my oil cap doesnt say anything except "ENGINE OIL". but I noticed a sticker underneath my hood that also specifies to use 5W-30 oil.
 

·
Registered
Joined
·
6,859 Posts
FWIIW, the 96-04 Mustang uses a simple on/off oil pressure sender. If the pressure is 6 PSI or higher, the sender is grounded. Less than 6 PSI, the sender is open.

The dash oil gauge deflection MEANS NOTHING. It has only two settings. Zero or about half way.

The challenge is to figure what the true oil pressure is. For example, is the low oil pressure a false alarm or is the oil pressure truely low?

Does the engine make any valve noise? If the oil pressure is low, likely the top end would make noise. Of course, if this were my car, I would not want to risk an engine without knowing for sure that the oil pressue is indeed OK.

The oil pressure sender is a cheap enough to replace it just for diagnostic purposes.

Inspect the wiring to/from the sender. Is it clean and tight? If the wire to the oil pressure sender is disconnected and grounded, does the dash gauge work?

Finally, consider getting a mechanical oil pressure gauge to measure the true oil pressure.
 

·
Registered
Joined
·
8,348 Posts
+1.....

I would suspect 2 things:

1. Bad oil filter. I have seen it happen.
2 Bad oil sending unit. It is located just behind your oil pump.(where the filter is) You will see the connector. If your car is running out of oil up top, it would sound like a diesel truck......

Don't get caught up so much about 5w-20 and 5w30 debate. The 5w-20 weight oil was used by Ford to meet CAFE requirements......
 

·
Registered
Joined
·
51 Posts
Discussion Starter #10
thanks for all the replies everyone!
now since this stock oil pressure sender is basically an on/off switch, it's probably in my best interest to purchase something a bit more advanced and functional, right?
i have done some driving around in my car (IE. back home from work) and I did not run into the same issues I was having this morning. I don't feel safe ignoring what did happen, so does anyone have suggestions on a mechanical gauge I could install in/on/near my dashboard to view an accurate reading all the time?

i am not sure what would be the best item (brand/product) that I should be looking for. would it be safe to skip over replacing the oil pressure sender if I am going to get a mechanical one?

thanks!
Tom
 

·
Registered
Joined
·
6,859 Posts
For the cost of a $18 sensor and 15 minutes worth of time, you will know one way or the other. That just seems so much easier than starting a "project" to add an mechanical oil pressure gauge.

Consider what is the annual Mustang production? Possibilly over 100,000 units per year. Guess what? They all have the same simple oil pressure sender. It is the best? No but IMO, there are really two issues going on here.

There's the possible low oil pressure, and then there's the fix the car so that it works like it was designed to. This keeps the resale value of the car up. It also prevents problems when someone else has to drive your car (Wife, GF, Mom).

IMO it would be so much easier to clean the wire and buy a new sender and replace it. If the dash gauge never gives you any more problems, consider it problem solved.

Otherwise, rent the oil pressure gauge from your local autoparts store and use it to TEST the oil pressure.
 

·
Registered
Joined
·
51 Posts
Discussion Starter #12

·
Registered
Joined
·
11 Posts
Ive been having the same problem with my 2000 v6, except mine happens when its cold, seems to go away once the car is warm? i dont know but it stressful.

Things ive done to try to fix,
used the stock ford filter (costed more, didnt fix the problem)
tried both 5-20 and 5-30 and they both do the same
but havent replaced the sensor yet

i dont hear any abnormal sounds from under the hood so im thinking sensor. but your not alone! it sucks

and as far as oil types, ive heard ford didnt start using 5-20 motor oil until about 2001 or 2002, unless your oil cap says 5-20 you should use 5-30, its what ive been told by lots of mechanics
 

·
Registered
Joined
·
6,158 Posts
+1.....

I would suspect 2 things:

1. Bad oil filter. I have seen it happen.
2 Bad oil sending unit. It is located just behind your oil pump.(where the filter is) You will see the connector. If your car is running out of oil up top, it would sound like a diesel truck......

Don't get caught up so much about 5w-20 and 5w30 debate. The 5w-20 weight oil was used by Ford to meet CAFE requirements......
#1 is what i was originally thinking..
#2 is what i thought of halfway through this thread
and using 5w20 vs 5w30 doesnt matter.. both are almost exactly the same neither will hurt the car and neither will make any difference that you can see or feel
 
1 - 14 of 14 Posts
Status
Not open for further replies.
Top