oil pressure drop after oil change?

[t7389sg]

I changed my oil today (first time for me and my new Alfa) in my 69 Spider Veloce and now the oil pressure is much lower than before the change. I also changed the two gas filters and the two air filters along with the two oil filters. Wow this car has a lot of filters. I found a lot of sludge on the oil filters. The SPICA filter had so much sludge you could barley make out the pleats. The main oil filter had a lot of sludge in the bottom of the canister as well. Before the oil and filter change my oil pressure was above 50 and never below 0 at idle. Now it does not get to 50 and is below 0 at idle. I searched this forum for oil recommendations and found a lot of spider owners use Mobil 1 15/50 so that is what I used. I found the main oil filter hard to get to so I removed the battery and tray to facilitate the removal. I found that the filter cartridge had some sort of rubber or fiber gasket on top and bottom of the filter. My new filter only came with a square O ring for the canister. I cleaned and then reused the 2 fiber/rubber gaskets on the new filter. I did have some oil leak out of the main oil filter when I first started the engine but it stopped leaking very quickly. I am worried that I have screwed up the fitment of the cartridge in the canister and that is why the oil pressure went south. Or maybe the sludge was holding the engine together. I have 2 old BMW airhead motorcycles that if you get the oil filter in wrong you will need a new engine. They call it the 3 thousand dollar o ring. Can anybody explain where I went wrong here? I look forward to your comments. Thanks.

[Stachowiak]

Hi,

The cartridge oil filter is a real pain. The "O" ring that ships with the filter is not always the correct one to fit the housing. I converted both of my 1750's to the spin on type made by Les Herlock. Here's the link to his site:

new brochure -filter.

I use Castrol GTX 20/50 conventional oil. Many people claim that the synthetic oils and old seals and gaskets don't mix well. I don't think your new filter is the cause of the low oil pressure, it's most likely the Mobil 1. From your description, it sounds like the engine hasn't had the best care and the last thing you need is to run it with low oil pressure. I would do an oil change with conventional oil and see if it helps. Also the Alfa gauges are not known for accuracy. You might want to connect a mechanical gauge and see what readings you get.

Dick Stachowiak
71 GTV
71 Spider

[t7389sg]

The O ring shipped with my filter was smaller than the canister. You called that correctly. I have always used Castrol GTX in my MG but I have been searching for another oil to use because of the ZDP missing now in Castrol. Someone here said that Mobil 1 still had it. I am not trying to start an oil discussion here. I just want better oil pressure and I don’t really have an alliance to any oil brand. I will look into that spin on conversion to save me from taking the car apart just to change a filter. This Alfa is in great shape, zero rust, and everything is here but it sat a long while in a garage. Not the best thing for a SPICA Alfa. I thought about hooking a mechanical gauge but I don’t posses one and I am not sure where to source on and where exactly to hook it up. Probably in place of the sending unit. Thank for your help. Steve G

[radamm]

On the occasions I needed to clean a neglected engine, I have used a "standard" oil with the inclusion of one quart of Dexron ATF. Dexron is an extremely "detergent" fluid. A fresh change with your choice oil in ~ 1000 miles will see a lot of the accumulated sludge flushed away. Your low oil pressure could be related to sludge inhibiting the action of the pressure relief valve in the pump circuit or the pressure sender. This debris could have been loosened by the shock of clean oil. I would run a more frequent oil change schedule for a few changes....oil cheap, clean engine-priceless!

Rick

[Elio Comello]

Again I agree, don't want to start an oil discussion thread...
However if you want to try a conventional oil with zinc..use Shell Rotella T 15W40.

TTFN Elio

[Alfar7]

Regardless of the "o-Ring" you are not loosing oil pressure in the oil filter unless it is leaking streams....

Loose the Mobile 1!
I does not have adequate anti scuffing (cam) protection. (zink additive)

After draining the Mobile 1 (don`t P&M cost of oil) add about 4 quarts of 20-50 Valvoline. Either Syn or petroleum. I suggest the latter, and have enough of it AND Valvoline 50 wt. (not 20-50) to finish filling up motor.
After the 4 quarts are in it start the motor and let it warm up and drive rationally and see what oil pressure is doing. If still low add one qt of 50 wt at a time to see what increasing the viscosity does to the oil pressure. If by the time the engine is full (8qts) and the oil pressure is not at least 15lbs idling hot, then I would suspect the motor was on a diet of heavy oil and viscosity index improvers to get the oil pressure up.
All the more reasons to get the Mobile 1 out!

Usually the #1 cause of low oil pressure at idle when faster RPM oil pressure is ok is wear in the head and cam bearing caps.
With those correctly repaired, oil pressure is generally excellent. Unfortunately, finding a mechanic competant to do that repair will take a bit or research on your part.
(Don`t listen to the crankshaft plug loss theory, at this point you would have knocking. )

[Tifosi]

Of course it could all just be because the actual idle speed is set way too low so that the pump is turning 'too slow'. (gotta check the most basic stuff first )

[Roadtrip]

At hot idle, is the oil low pressure light on? It is permissible for the gauge to show zero at idle, as long as the oil low pressure light (set to trip at 5 psi) is NOT on. The gauge is not terribly accurate.

I agree with changing to a spin-on filter. Those cannister filters are a totally unnecessary PIA.

[lowmileage]

First off, if you are relying on the stock Alfa gauge, forget it. Hopefully at idle you are not hearing any "knocking." Mobil 1 15-50 supposingly has enough zinc (1200 ppm). On these pre-Syn engines, I like dino oils. Castrol 20w-50, long the Alfa's owners favorite, now only has 800 ppm zinc. Nice of Castrol to make us aware of this change. FWIW, I now use 6 qts Delo 400 15w-40 (with 1200ppm zinc) added with 2-15 oz. bottles of red GTX which has an additional zinc supplement. I think it's good stuff. I was reading on my stock Alfa gauge 0 at (hot) idle and 50 lbs running. I added on a Autometer electric gauge which shows 15 lbs at hot idle and 75 lbs running. I even changed my sender which gave a little better, but still not accurate results on the stock gauge.

[lowmileage]

Quote:

Originally Posted by Roadtrip The gauge is not terribly accurate.

[t7389sg]

I will change the Mobil 1 out this week with a new PIA filter. I will use some dino type oil. I like what Alfar7 suggested and will probably go with his recommendations. I drove the car on Sunday and the oil pressure seemed to fluctuate between a high of 57 lbs and a little above 0. Sometimes at idle it is 7 lbs and sometimes below 0. It’s like some sludge is moving around and clogging something and then it clears. The oil light has never lit because it does not work I replaced the bulb but no joy. I need to get a wire schematic and trace the fault. There is a sender on the oil filter housing. Is that for the light or gauge? The engine does not knock and in fact is running great. It fast idles at around 1100 cold and drops to 700 or 800 when hot. It seems I am not as doomed as I originally thought. If the oil change does not help I have no problem pulling the head and sending it of for a restore because I love this car. Where does everybody like for Alfa heads (just in case)? Thanks for all the help. This website makes owning one of these cars easy. Steve G

[Roadtrip]

The sending unit on the filter housing is for the light. The gauge sending unit is on the rear right side of the engine. It's possible that the gauge sending unit is defective. The light sending unit is simply an on-off grounding type switch that you can test with a test light. One lead to the + battery and the negative to the tang on the sending unit. If the oil pressure drops below 5 psi, the switch ground and turns on the light.

Never start tearing down an engine for oil pressure without check the exact pressure with a direct read gauge. Alfa gauge sending units are notorious for going bad.

[lowmileage]

Differences between gauges. yea, yea yea - I know it's not that clear. Alfa dash gauge reading 55 lbs, Autometer (top accessory) gauge at 75 lbs. After spending 50 bucks for a new sender too.

This is initial (cold) start up readings. My low hot idle is 15 lbs (min) actual on the Autometer gauge.

[PJN]

I was told that low oil pressure at idle is normal. I to was concerned about the drop, but was told it is normal. Now I am worried again!?!

pjn

[lowmileage]

Quote:

Originally Posted by PJN I was told that low oil pressure at idle is normal. I to was concerned about the drop, but was told it is normal. Now I am worried again!?! pjn