too much oil pressure???

[6969ronin6969]

Just curious, I've got a '56 TR3 with a later TR3A engine in her (don't remember the engine # right now). I don't have paperwork related to the engine change so I have no idea when it occured, but I'd guess the engine was at least freshened up (new gaskets, etc.) to possibly fully rebuilt sometime in the past. The car pulls strong and doesn't leak.

All this is background to my main question, can you have too much oil pressure? When I first start the car and am accelerating the oil pressure gauge is pushing the 100psi tick. At idle it'll still stay around 80. Once everything warms up the gauge still stays somewhere around 60psi in motion and drop closer to 50 at idle. So do I have a problem? If so, what could be causing it.

I've had the car ~2 years and it's always been like that.

Thanks,

Eric

 

[TR3driver]

The higher pressure won't necessarily harm anything, but it does increase the strain on the oil pump/distributor drive and make leaks around the filter canister more likely.

If it were my car, I would first try to double-check the gauge reading (those old mechanical gauges sometimes read high), and then turn down the pressure relief valve (funny screw on the oil filter head looks like it has a large nut and a small nut) to get the book value of 70-80 psi when cold.

 

[6969ronin6969]

Thanks Randall. One more question, I have an aftermarket set up to run a spin on filter. Do you know if it will still have the pressure relief valve on it?

Thanks again,

Eric

 

[70herald]

If you are basing this on the ~50 year old gauge in the car I would guess that the problem is the gauge reading to high.
Check it with a known good gauge first.

Also does the gauge actually return to 0?

 

[Andrew Mace]

I agree pretty much with all the advice above. OTOH, those numbers quoted aren't too outrageous, especially if you're using a decent 20W-50 oil.

One other thought: could the pressure relief valve need cleaning, i.e., it's not "relieving" properly due to whatever?

 

[TR3driver]

I have an aftermarket set up to run a spin on filter. Do you know if it will still have the pressure relief valve on it?

Yes, a pressure relief valve is required and cannot be in the spin-on filter. Depends on which setup you have, but by far the most common spin-on conversion retains the original filter head (and its PRV).

 

[TomMull]

Agree with Randall on checking the gauge. The relief valve is not a sophisticated device, rather a spring loaded stopper that comes loose at a given pressure which stops further rise. It has little or no effect at low pressure i.e. less than 70 or so. Since you seem to be about 15% above normal at all temperatures, the gauge would be suspect (or oil viscosity too high).
It is my experience that 90+ pounds in winter cold is not unusual, particularly with a fresh engine but it should drop to 50ish at speed when hot. Note that where I am in New Hampshire, the oil may may take a half hour or more to heat up (long after the coolant is normal) and may never get hot on a really cold day. Don't know how cold it is where you are but it's possible that you readings are normal and the weather is at fault.

 

[Member 10617]

When I start out on a cold day, my oil pressure usually rises to 90+, but after about 20 minutes or so, it will settle down to 50 and below at idle. It has been doing this ever since I had the engine rebuilt and a spin-on oil filter installed about 9 months ago.

I have no leaks around the oil filter.

I use Brad Penn Grade 1 Racing 20w50 Semi-synthetic oil and change it every 2000 miles.

All gauges except the oil pressure and fuel gauge have been rebuilt.

No matter what the ambient temperature, my temperature gauge -- when the car has warmed up -- remains at between 180 and 185, never higher.

 

[glemon]

Maybe the Castrol Syntec 5w-50 discussed elsewhere on the forum recently would be a quck easy fix for high pressure at start up?

 

[6969ronin6969]

Thanks for all the feedback! It sounds like my situation isn't unique so that makes me feel better. i will still check out the pressure with another gauge just to double check, but my experience sounds similar to a couple of you. It's been in the 40s and 50s around here recently so it sounds like the high oil pressure is not out of line.

Thanks again!

Eric

 

[glemon]

Yeah, I will add that my TR4A displayed similar high readings after rebuild (no problems resulted, drove it for many years) and my TR250 was going to 100 pounds on start up from cold engine on a warm day until I put a washer in place to weaken the tension on the relief valve spring, which brought it down to about 80.

 

[TomMull]

The relief on the TR3,4 is adjustable, though not recommended, so a washer would not be necessary. I don't know about the TR250 but I think adding a washer to the TR3,4 would increase the relief pressure point. Tom

 

[poolboy]

I imagine that on the 250, glemon would have put the washer between the external housing and the engine block so that the housing would not compresss the spring as much, requiring less OP to open the valve.
On the other hand, putting a washer over the shaft of the piston, then the spring over the shaft in the usual manner would increase the spring pressure, holding the bypass (relief) valve closed until greater pressure developed.
I've done both (on different engines).

 

[Hap Waldrop]

A little shimming off the pessure relief valve will normally buy you a little improvement in cold oil presure and on the accelerator oil pressure , but not much in the way of hot oil idle oil pressure, normally lower than expect oil presure is the culprit of too much main or more likely too much rod clearence, but it always easier to try the pressure relief valve first, because too much rod or main clearence means a rebuild.

 

[TomMull]

Hap,
Perhaps I'm confused here but it seems to me that (at least on the TR3), the ball bearing (seal) under the relief spring seats in the bottom of the pressure relief body, so by adding a washer to the body would move the whole assembly away from the block but have no effect on the relief pressure.
It would be nice if I'm wrong here since adding a washer is easily reversible, messing with the adjusting screw is not.
Tom

 

[glemon]

Sorry to muddy the waters, the 6 cylinders don't have an adjustable thing as noted, fitting an extra washer as I did would be the equivalent of screwing the tensioner out a bit on the adjustable ones.

 

[Hap Waldrop]

Tom, sorry for the confusion I'm speaking more of Spitfire and TR6 engines. Looking at those they could be made adjustable as well. I currently make my MG A series engine to have adjsutable presure relief valves, they are located in a place that is convienent to get to them, they can actually be adjusted while the engine is running.

 

[Member 10617]

I'd like to revisit this question.

I took a 126-mile roadtrip today as we are experiencing unusually warm weather in Virginia this week (it won't last). The ambient temperature was about 65-68 degrees.

As usual, when I started my car cold, the oil pressure registered about 90 and fell very slowly as the engine warmed up on the road.

Normally, the car temperature runs at 185 (solid), but today it held at about 180 for the entire trip.

Also, normally, the car at this temperature runs at oil pressure of 50 + or - a little. Today, however, it ran almost consistently at two clicks abouve 50, dropping to 50 only now and then at steady speed and level ground (about 2000 rpm). It dropped, as usual, to abut 30 when idling at lights, etc.

Does that difference in temperature help to explain the higher than "normal" oil pressure? I know that running at two clicks above 50 is probably just fine, but it is a little unusual on my car.

The engine is "new" (i.e. rebuilt -- has 4000 miles on it). The gauge is old -- probably original. Should I suspect the gauge?


Any thoughts?

 

[tdskip]

You need to check the gauge at this point, but this is the kind of problem you should be happy to have. Too little oil pressure is usually the issue. I'd not worry about this much.

 

[Member 10617]

Since I'm new to this, I'm glad to learn that the oil pressure I'm seeing is good. I am thankful that the oil pressure and temperature on the car are much improved since having the engine rebuilt. I am especially happy about the temperature -- holds at 185 even when the ambient temperature around here is near 100 and I'm climbing mountains -- since years ago when I had a TR3 in Arizona it was always overheating.

I've had just about all the guages "rebuilt". I guess the oil pressure guage will be next.