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Discussion Starter · #1 ·
I have an 04 GT that I just replaced both lash adjusters on cylinder 1 due to excessive tapping yesterday. When I was out driving it today and stuck in traffic the oil pressure gauge dropped all the way down then bounced back up a couple times before finally dropping and staying that way. I also noticed an increased amount of engine tap like it was low on oil. Stopped and checked the oil level and it was fine. Started it back up and pressure came back up. It did the same thing this evening. Does anyone have any idea what might be causing this? I'd assume it was the sending unit acting up if it wasn't for the extra engine noise like it was low on oil.
 

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Don't know, but you have me worried. An oil pressure switch that is going bad will show normal then zero, then normal. But, you also noticed a different engine noise. That indicates that you are actually loosing oil pressure. Check your oil level first. If that is OK then I would suspect an oil pump problem.
 

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Discussion Starter · #3 ·
I know I've got a valve cover leak on that side now, but everything else looks fine. Checked oil again and it's dead on. Lost pressure again today, came back on it's own bouncing on and off a few times and then right back down. Odd thing is if you shut the car off and start it right back up the pressure comes back.
 

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Sounds like your oil pump might be getting ready to **** the bed. The oil pressure gauge is not really a gauge as much as it is an on/off switch. It is designed to show pressure anytime the sensor senses anything over 6psi. Sometimes those go bad and you have to replace the sensor, but if you're getting engine noises along with it, I'm with Eagle, you might have bigger problems.
 

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honestly sounds like there is sludge build up in the pan around the pickup tube. the sludge might be clogging the pickup but then breaks free. this could be the cause of your problem. i would suggest dropping the oil pan and checking everything out. if there is a lot of sludge, clean your pan with brake parts cleaner, put in fresh oil and run an engine detergent (any auto parts store has it) because the sludge may be pushed trough the entire engine. change your oil again and you should be good. if the pickup tube to the oil pump has a lot of crud in it, i would suggest a new oil pump, cause if the tube is gunked up so is the pump. the oil pump is not hard to change, just follow the repair manual. hopefully you wont have to tho, i think an engine flush will do it. i had the same symptoms in a crown vic about a year ago (they have the 4.6 2v also) and thats what i did. hope this helps.
 

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Discussion Starter · #6 ·
Unfortunately that's what I was afraid of. Any good recommendations on pumps if it is going out? I've been trying to build the car a little at a time as it needs stuff done. Maybe a high volume replacement or are they not necessary in the stangs?
 

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Usually when I see oil pressure bounce down then back up its a spun bearing. It loses pressure when it spins, but it will catch in place again, allowing the pressure to return. I can't think of what in the oil pump would cause the up and down like that ...seems to me it would just break and that's it. Unless maybe there's an issue with the key and crank snout. Any metal shavings in the oil?
 

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I wouldn't do a biggest volume pump without a 7qt pan. Stock replacement should be fine


Sent from AutoGuide.com App
 

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Discussion Starter · #9 ·
No shavings that I've seen in it. It does still have a distinctive tapping, but it doesn't trace the RPM's and sounds to be in the top end. I'm pretty sure the timing chain has some slack in it. Car has 153,000 miles.
 

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Might be a good idea to buy a cheap mechanical OP gauge and install it just to make sure its not just a bad sender. I believe theres a threaded port right on the oil filter adapter...that will give you an exact idea of what pressure the mains are directly seeing. I would drain the oil and replace the filter as well. Look for metal or sparkley stuff in the old oil and cut the old filter open for inspection. If it is truely losing oil pressure, your not doing it any favors by running it. If there is metal in the oil, then your pretty much done dealing. If no metal, then it would almost have to be the oil pickup tube (maybe plugged or coming lose?) or the oil pump. Has the engine had regular oil changes?
 

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Discussion Starter · #13 ·
I couldn't tell you about the service history prior to me buying the car, but it didn't look promising. Purchased it with just over 120,000 miles. Still had what appeared to be the factory fuel filter, k&n filter is not installed properly and was filthy. The plugs were beyond shot. Since then it's had regular oil changes, new fuel filter, new plugs, tranny rebuild, new alternator, new water pump, new a/c clutch, new idler pullies, trick flow track heat intake manifold (factory was leaking coolant at the o-ring for the filler neck), new thermostat, new wheel hubs, new strange struts up front, new sway bar bushings, new end links, new spring isolators, mm caster camber plates, mm solid rack bushings, brembo front rotors, new pads, new lash adjusters on cylinder's 1 & 2, and a few other misc things. I did notice when I had the valve cover off that there is a distinct smell of burnt oil.
 

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Sounds like its been rode hard and put away wet, lol. Hope it turns out to be something simple, but if not, think of it as an "opportunity for justified improvement". It's like having a baby-the timing is never right, but afterward, you wonder why you waited and put it off.
 

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Your cold oil pressure will be 100psi with a cobra pump and close to that in the upper rpms. I run one with TSS billet gears and a stock gt pressure spring. My cold oil pressure is 75psi.
 

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There is a possibility that your oil pickup tube is partially clogged.
 

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Discussion Starter · #19 ·
Just an update and thank you for all the suggestions you guys had. Tore into it over the weekend. Turned out the lower left timing chain guide had busted. A couple large pieces were still by the chain, but most was in the pan. The screen on the sump was completely clogged with small pieces of the guide and sludge. It's looking more and more like this car was very poorly maintained before I got it. While we had the K out we also noticed both motor mounts were shot so they were replaced too. It's once again back up and running with great oil pressure and the tap is gone.
 
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