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  #1   IP: 74.230.49.250
Old 04-26-2007, 10:30 AM
skhorleb skhorleb is offline
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low oil pressure after rebuild

Hi everyone.

Recently completed a lot of rebuild activities on a late model A4 while the engine was still on the boat...including acid dipped head and manifold, machined head and manifold, cleaned out all oil and water ports, new head and manifold studs, new head and manifold gaskets, new aftermarket thermostat, rebuilt carb and mechanical fuel pump, new plugs and wires, new coil, replaced water pump, new starter, repainted engine, etc. I saw no need to replace pistons, rings, or valves. Already had installed electronic ignition.

Before the rebuild my oil pressure was at about 45 PSI. After the rebuild I found my oil pressure diminished to less than 20 PSI while cylinder compression remains very good. Operating temp is dependable, between 140 - 170 degrees. 'Thought maybe my old oil pressure gauge or sender was bad, so I replaced them both. New Teleflex gauge and sender shows oil pressure at 10-15 PSI, barely high enough to avoid triggering the oil pressure alarm. I cannot explain the symptom after replacing the instrument and retorging everything a few times.

Is it likely that cleaning out all of the oil and coolant ports and the improved lubrication flow would account for the severely diminished oil pressure? Thanks.
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Old 04-26-2007, 12:08 PM
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Steve:

Nothing in your report would give me a clue as to why your oil pressure would be lower now than before your work, including the fact that you cleaned out the oil passages. Did you try to adjust the regulating valve?

Don
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Old 04-26-2007, 11:00 PM
skhorleb skhorleb is offline
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yet to adjust the oil pressure regulating valve

Hi Don,

Thanks for the quick response.

No, I did not adjust the regulating valve yet. I wanted to touch base with you first before tweaking anything first...in case there was some subtlety I overlooked. I plan on doing that tomorrow.

Before I adjust the pressure value, I am going to take off the oil pressure sensor again and run a 14 gauge copper wire through the 1/8th" brass fitting between the block and the sensor in case there is some obstruction. Although it is far fetched, I wonder if clearing all of the oil ports introduced some gunk to the crankcase which has partially obstructed the oil flow from the block to the sensor. Although I changed the oil after my engine work, that is the only possible explanation I can come up with.
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Old 04-27-2007, 08:30 AM
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You could have someone turn the starter over a second or so while you catch the oil coming out of the sensor hole in a rag. If there is anything there, it will come out in your rag.

Don
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Old 04-27-2007, 10:26 PM
skhorleb skhorleb is offline
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Adjusting oil pressure does not change anything

Don,

Before I got your email, I ran the copper wire through the oil sensor hole and it was unobstructed. I then adjusted the oil pressure valve. Still no change in the oil pressure guage...even after turning the value clockwise 7 or 8 revolutions. There was plenty of oil on the internal shaft of the pressure value adjustment. 'Have not had a chance to verify that oil comes out sensor hole when the engine is briefly cranked.

I am going to replace the sensor wire next.

Any other ideas that could account for the problem?

Thanks.
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Old 04-28-2007, 09:45 AM
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I still don't see anything in your work that would have had any effect (one way or the other) on your oil pressure, with the possible exception of your "cleaning out all oil ports". Could you explain exactly how you did that?

Don
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Old 04-28-2007, 05:38 PM
skhorleb skhorleb is offline
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cleaning oil ports

Don,

You asked what I did to clean the oil ports. While I had the head removed, many of the oil passages on the top of the block were obviously blocked. I ran a (3/16"?) drill bit down through each opening by hand, twisting it and wiping gunk off the bit as I went. I cannot recall exactly how many clogged passages I found, but when I was done, they all seemed clear. I did not use a power drill for risk of damaging the crank shaft if the drill moved too aggressively.

Do you think that might be related to the low oiil pressure?
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Old 04-28-2007, 09:40 PM
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There are no oil passages between the block and head, which makes your report even more perplexing. It now seems to be the case that you didn't do anything to alter the oil system which would in any way explain your low oil pressure.

Don
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Old 05-14-2007, 09:30 PM
skhorleb skhorleb is offline
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unexplained low oil pressure

Don,

Based on your last response, the passages that I cleaned out during my rebuild efforts are obviously not oil ports. Rather, they must be coolant ports that connect between the block and the cylinder head. They open through the top surface of the block.

I have since replaced the 16g wire connecting the oil pressure sender to the oil pressure gauge. No improvement. (As a recap, I installed a new Teleflex oil pressure gauge, Teleflex oil pressure sender, and new wire.) Still unable to explain why my oil pressure suddenly dropped so low after the rebuild.

I wonder if the onset of the low oil pressure symptom is merely coincidence to the partial rebuild completed a couple months ago.

Desperate to isolate the problem, here is one other detail: I notice oil is now splattered behind the engine as if it were being thrown off the drive shaft next to the engine output coupling. Oil is on the engine compartment walls rear of the engine. This was never noticed before. Whenever I touch the engine output coupling there is always a drop of oil ready to drip from it. Is it most likely that the oil is coming from a bad rear oil seal?

I believe this area has had a very slow oil leak as oil has been repeatedly found in the lowest part of the bilge ever since I owned the boat. I was never quite sure where the oil was coming but it always reappeared after cleaning out the bilge with degreaser, bilge cleaner, etc. Behind the oil pan is the only oily location under the engine.

Now for the $50 question: Could a bad rear seal account for the inability to improve the oil pressure above 12-15 PSI regardless of the number of clockwise turns of the oil pressure adjusting screw?

Thanks.
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Old 05-15-2007, 08:56 AM
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Steve,

Sorry, but your apparently leaky rear oil seal would not explain your low oil pressure. You would have to lose all but approximately one quart of oil before the oil pump would cavitate and dump your pressure.

I think (before doing anything more complicated) I'd install a direct reading gauge to verify your pressure. Any 0 to 100 psi water gauge from a local hardware store or Home Depot will work. To get absolutely accurate indications, you should install a small valve (the small valves used in a refrigerator water supply work well) to snub oscillations in your indications.

Don
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Old 05-15-2007, 12:08 PM
baileyem baileyem is offline
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Low oil pressure after rebuild

Is it possible that some of the gunk that was mostlikely dislodged during your rebuilding operations is stuck in the oil pressure adjusting port? It seems that if you turned the adjusting screw that many turns without effect that there could be a problem with the oil pressure adjuster.
MM sells a great little kit for resurfacing the oil pressure adjuster's valve seat and also has replacement valve set-ups for sale. They work great.

Mike
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Old 05-27-2007, 10:02 PM
skhorleb skhorleb is offline
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Unable to diagnose cause of low oil pressure

Hi Don,

I followed your advice--installed a direct reading gauge to verify the pressure. The mechanical gauge virtually matches my electrical oil pressure readings--about 8 - 10 PSI.

Throwing money at the problem, I also replaced the oil pressure adjustment valve with one I purchased from MMI. That did not improve the oil pressure either...even when I screwed the value in the whole way.

Do you think something is obstructing the oil pressure adjustment valve from properly seating?

I am still totally perplexed. My oil level is full. Other than low oil pressure, I detect no other issues. Temperature is good. The engine runs like a top...After sitting for a week or more, it immediately starts with just a slight turn of the key and then shut off the choke within 5 - 10 seconds. It does not miss, even when cold. Very smooth. It does not sound unusually tight or labored. No noises like pinging, rattling, or squeaking.

I cannot imagine oil selection would cause my oil pressure problem, but since my rebuild activities I started running Mobil1 10W30 synthetic oil in the engine. I have about 5 - 7 hours on the engine since the rebuild, so I doubt the oil's viscosity is being compromised.

Living along the Alabama coast, should I try a heavier oil?

I am growing leery about starting the engine and running it for just a few minutes. I may be an alarmist, but is the low oil pressure causing any damage to the engine?

As always, thanks!
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Old 05-28-2007, 10:07 PM
skhorleb skhorleb is offline
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Contaminated synthetic oil and low oil pressure

Don,

Eureka! I discovered the low oil pressure was associated with the synthetic oil--Mobil1 10W30 synthetic--used only after my partial rebuild. I immediately knew something was wrong this morning when I hand pumped it out of the crankcase. It was noticeably very thin....viscosity was not much thicker than whole milk. I replaced it with good ole' standard 30W detergent oil--what had been used before the rebuild. Voilà! The oil pressure immediately jumped up to 80+ PSI. I backed off the new oil pressure regulating valve about 5-7 revolutions and it stabilized just under 40 PSI. My TLC program had run amuck...in this instance.

Hopefully others will find this experience useful. I won't be using 100% synthetic oil again in this application. After some reading, I learned that synthetic oil typically reduces oil pressure 5-10 PSI and may lead to leaky seals in older engines. I am not criticizing the Exxon/Mobil Corp or synthetic oil. I previously owned Mobil stock and use Mobil1 100% synthetic religiously in my cars and John Deere tractor. However, I caution others who might use it in this application.

I am not sure why I had this bad experience, had never encountered similar problems from an oil change, but after some thought I have a couple theories. 1.) This was the first time that synthetic oil had been used in this engine. No doubt some standard detergent oil was still in the oil system. Possibly residue from the old detergent oil led to the contamination. 2.) I understand that Mobil1 synthetic oil has shelf life of 5 years. I used an unopened 5 quart container of Mobil1 that had been in my garage for possibly 3 1/2 years. I could find no date on the container….hmmmm.
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