Oil pressure too high?

[Zmanco]

As I said in another post, I'm in the final stages working out a few issues after going turbo. Quick recap: I picked up an engine pulled in 1982 from a 280zx turbo with less than 100 miles. I already had a P90 head, intake manifold, megasquirt etc. So basically all I used from the turbo motor was the bottom end (untouched) with its oil pump and the timing cover.

 

For the first 1700 miles all was good and then suddenly I noticed I had oil pooling on the bottom of the oil pump. It seemed to be coming from below the water inlet on the passenger side but there was no obvious source. Eventually I determined that it was seeping between the timing cover and block. So I pulled the cover off hoping to see that I had damaged the gasket or something. But alas there was no visible damage in any way. So I used the old timing cover from my previous engine and used it. Well, the leak remains, albeit not as much.

 

So now I'm thinking that the oil pressure may be too high. My oil pressure gauge (I know - on the 73's they are notoriously inaccurate) reads about the same as with the old motor which I expected since I had moved the old sending unit over to the new motor. Still, I pulled the over-pressure valve and spring out of the new oil pump and they looked fine. As an experiment I put the old engine's spring in yet the pressure still reads the same and the seepage continues, although it's not as bad as it was before I changed the timing cover.

 

So to recap,

- For the first 1500 miles there was no oil leak at all

- Suddenly the seepage began

- The seepage continues with the replaced timing cover

- Putting an old pressure spring into the "new" oil pump didn't solve it.

 

If you look at the picture of the timing cover, you can see where I circled the output of the pump back into the block. That's right where the oil is seeping which makes me think my oil pressure might be too high. But why that be the case even with the old spring? What am I missing?

 

FYI, I have an oil cooler using one of the Earl's fittings that sandwiches between the oil filter and block. But this was all installed before the swap and never gave me any problems so I'm assuming it's not the issue here.

 

Suggestions?

[JMortensen]

Get a cheap mechanical gauge and see what it really is. Then you're not chasing problems that don't exist. I had a pump that put out over 100 psi cold and it didn't leak until I put an adjustable relief valve screw on it, so I don't think the leak is a sign of too much pressure, it's the sign of a bad seal against the timing cover.

[Zmanco]

I was thinking of trying a mechanical gauge, but remembered a discussion about the sensor threads being BPT. Anyone know of a kit that uses a BPT sensor, or know where I can find a BPT to NPT adapter?

 

EDIT: I just found this on Summit:

http://www.summitracing.com/parts/ATM-2269/.

BSPT is the same thing as BPT, correct? Would this fit L6 block?

 

As for the leak being a sealing issue between the cover and block, I initially thought that and hence tried a different (and known-good) cover. I'm now wondering about the block surface, but it looked good when I had the cover off, and I scraped it with a razor and cleaned with solvent to be sure it was pristine. So I'm not sure what I would do next assuming it's not an excessive pressure issue? Any suggestions?

[Zmanco]

Update: the oil is still seeping, but much less than with the original install. Last night I put a mechanical gauge on and the max pressure is 50 psi. It hits that by 4k rpm and never goes higher. So clearly it's not an excessive pressure situation.

 

Side note: the notoriously inaccurate oil pressure gauge is just that - inaccurate. It's reading around 75 psi when in fact it's only 50 (assuming the mechanical gauge was accurate of course).

 

I'm still confused why this is happening as the block surface was clean (scraped with razor and cleaned with brake cleaner) as were both timing covers.

 

I suppose there's no harm in just driving it and wiping the area down regularly, but it's frustrating to have an oil leak on this otherwise very clean engine.

 

Anyone else had this happen before?

[JMortensen]

50 psi isn't enough at say 6 or 7K rpm. The rule of thumb is 10 psi per 1000 rpm. Did the gauge you bought use a ferrule, and if it did use one are you sure you got it installed correctly? Mine came with plastic tubing and I tried the provided ferrule and ended up with a gauge that was very slow to react and read low. I fixed the ferrule and used copper tube and suddenly the gauge responded instantaneously and accurately.

[Zmanco]

It did have a brass ferrule and plastic tubing. The gauge response was a little sluggish, but I thought that was due to the trapped air in the line acting as a spring as the pressure changed. There wasn't much to installing the ferrule - it's cone-shaped and can only fit one way. When I pulled it off it looked fine - no weird dents or distortions, although I wasn't specifically looking for anything in particular.

 

How would installing it incorrectly affect the readings? Are you saying that it could perhaps pinch the tubing and affect it that way? Wouldn't holding a sustained rpm cause the pressure to eventually equalize and become accurate, albeit it might take a few seconds?

[MAG58]

A quick fix for gauge adaptors is go in to your favorite local auto parts store and ask for a gauge adaptor for a mini (Classic)/MG/Triumph etc. basically any old popular brit car. They usually have one on hand and it wont take as long to get one from summit.

[Zmanco]

I used an inexpensive mechanical oil pressure gauge and an NPT to BPT adapter from Summit. MAG58, is that what you're referring to?

[JMortensen]

How would installing it incorrectly affect the readings? Are you saying that it could perhaps pinch the tubing and affect it that way? Wouldn't holding a sustained rpm cause the pressure to eventually equalize and become accurate, albeit it might take a few seconds?

Maybe. Not sure. All I know is that the plastic tube pinched in mine and I determined that it didn't read accurately, then after I went to the copper tubing it did (tubing is cheap, BTW). If 50 lbs is accurate, I would do something to up the pressure. New pump, comp springs, shim the stock spring, etc.

[softopz]

When you replaced the timing cover did you re use the gasket? if so did you put sealer in the areas that is recommended in the fsm? How about the oil pump gaskets these are very thin and it doesnt take much for them to leak.

[MAG58]

I used an inexpensive mechanical oil pressure gauge and an NPT to BPT adapter from Summit. MAG58, is that what you're referring to?

yep. When I hooked up my mechanical gauge, I just snagged the little adapter off of a spare mini block I had. Works like a charm.

 

BTW, what are your readings?

[Zmanco]

When you replaced the timing cover did you re use the gasket? if so did you put sealer in the areas that is recommended in the fsm? How about the oil pump gaskets these are very thin and it doesnt take much for them to leak.

Yes, new gasket. I scraped all the old gasket off and cleaned all the surfaces with brake cleaner.

 

As for the FSM, no, didn't realize there was supposed to be sealer used for the timing cover. The first time I assembled an L engine I followed the FSM, but don't remember any reference to it. Since then I've put timing covers on at least half a dozen times. Every time I did it dry going from memory, so not sure why this time was different. But I'll pull the old FSM out and see what it says.

[Zmanco]

Readings are:

 

RPM Pressure

750 ~5 psi

1000 10

1500 18

2000 28

2500 38

3000 45

3500 47

4000 50

>4000 50

 

This is with relatively new 5w30 Mobil 1 synthetic after driving for about 15 minutes to get some heat in it. But I do have an oil cooler and it was about 45 F ambient.

 

If 50 lbs is accurate, I would do something to up the pressure. New pump, comp springs, shim the stock spring, etc.

The pump came from the donor turbo engine which had less than 100 miles on it. I did swap the spring with another pump and it didn't make any difference. I'm thinking/hoping the gauge was reading low. I guess I'll find some copper tubing and try again. But the ferrels are slightly compressed at the thinnest part so it may be hard to slide them over the new tubing. I'll have to look more closely tonight to see if they're closed up too much. That would appear to explain the low readings - if that's what happened.

[MAG58]

Readings are:

 

RPM Pressure

750 ~5 psi

1000 10

1500 18

2000 28

2500 38

3000 45

3500 47

4000 50

>4000 50

 

This is with relatively new 5w30 Mobil 1 synthetic after driving for about 15 minutes to get some heat in it. But I do have an oil cooler and it was about 45 F ambient.

 

The pump came from the donor turbo engine which had less than 100 miles on it. I did swap the spring with another pump and it didn't make any difference. I'm thinking/hoping the gauge was reading low. I guess I'll find some copper tubing and try again. But the ferrels are slightly compressed at the thinnest part so it may be hard to slide them over the new tubing. I'll have to look more closely tonight to see if they're closed up too much. That would appear to explain the low readings - if that's what happened.

 

With only 50psi, you really should only spin your motor 5k, which I think is a little low. Perhaps a little thicker weight oil? In my freshly rebuilt L28 (.002 on the mains and .0025 on the rods, clearance) I run 10W-40 Brad-Penn Oil, and start at about 24psi at Idle (850rpm +/- 50) and up to about 50 at 2k and 70 at 3k.

[Zmanco]

I checked around and wasn't able to find any small tubing at the local shops so reconnected the mechanical gauge using the plastic hose and ferrules. I cut the old ends off and paid close attention to make sure that nothing was crimped or blocked.

 

When cold, I was able to get a max pressure of 55 psi on the gauge, and when warm it was still 50-52 once above 4k rpm.

 

So I'm confused now based on the following information:

 

- This pump has less than 2k miles on it and came from a stock 280zx turbo.

- I get the same max pressure when I use the spring from the pump from my old engine.

- Ignoring for the moment that the stock gauge can't be read literally, it still read somewhat higher pressures with this engine than it did with the old engine. That one I put almost 30k miles on, including many track days where revs were mostly between 4k - 7k. My assumption is that I didn't have an oil pressure problem with that engine, and this one reads slightly higher pressure using the same sending unit and gauge.

- The mechanical gauge I bought from Summit is an el cheapo:

http://www.summitracing.com/parts/SUM-G2924/ How accurate are these? Could it be off by 15 - 20 psi?

- I've got almost 3k miles on this engine all street driven, but haven't been shy about taking it to 7k rpm often. If it really was only seeing 50 psi, albeit with 5w30 synthetic and an oil cooler, should I expect to begin to see issues with wear and hence oil consumption or smoke? Right now there is no smoke nor is it burning any oil.

 

So I'm not sure what to do next.

1. I suppose I could buy a higher quality gauge, but hate to spend the $$$ for something I'll not use again. Maybe I have to look at it as insurance?

 

2. I could put my old non-turbo oil pump in and see if that changes the readings. But if it reads low as well, can I safely conclude it's the cheap gauge?

 

3. I could just buy a new turbo oil pump. They're $74 at MSA. Maybe look at this as insurance?

 

I'm leaning towards #3, but would appreciate any other ideas.

 

And of course, none of this addresses the original issue of the oil seepage/leak. Ugh.

[Zmanco]

Today I remembered that the fuel pressure gauge I have installed on the engine has the same NPT fitting as the mechanical gauge so I temporarily connected it. I didn't test at all the rpm points, but above 4k rpm it peaked at 52 psi which is pretty close to the mechanical gauge.

 

Next I went through the 82 280zx FSM trying to find the factory spec for oil pressure, but if it's in there, I can't find it. I know the rule of thumb is 10 psi per 1k rpm, but at the same time, remember a recent thread on oil where the real issue is getting enough volume of oil throughout the engine, and the actual pressure isn't so important. As I'm currently running 5w30 synthetic, I'm wondering if there really is anything I need to be concerned about?

 

Also, the pressure levels off after 4k, which leads me to believe that limit to pressure is from the relief valve/spring, not a worn oil pump. Someone please check my reasoning here: if the pump was worn and the relief valve wasn't limiting the pressure, wouldn't it continue to rise with revs? And I've tried this with 2 valve springs and obtained the same readings, so figure it's not due to a worn spring.

 

So what do the experts think? Should I put a washer under the spring to increase the pressure? Or do I just buy a new pump from MSA? Or do I accept that the 10 psi/1k rpm rule is just a guideline and not worry about it?

 

Lastly, does anyone know the factory spec for oil pressure?

[Zmanco]

Ok, after discussing with some of the locals including slownrusty, I decided to shim the spring. 3 washers totaling 0.185" seems to have done it, although I'll have to wait until the snow melts and I can get some temp beyond idling in the garage.