TR6 High oil pressure in TR6

My oil pressure seems too high. At idle it's around 55-60psi but at 2500rpm's and over the pressure rises and stays around 80-95 psi. I also notice oil oozing from the dipstick area. Any idea what is causing the problem?

Thanks,

Gene

This sounds to me like an oil pressure relief valve problem. Did the problem develop suddenly? If so, I'd suspect that the valve is stuck. You might try removing it and cleaning it. If you decide to remove the valve to clean it, there are precautions you need to take not to disturb the adjustment screw. I've personally never removed/cleaned mine, so perhaps someone here with a little first hand experience will jump in and offer more detailed assistance.

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... You might try removing it and cleaning it. If you decide to remove the valve to clean it, there are precautions...

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In my archives I found this...

"On the TRactor motor, the relief valve is fairly easy to remove and clean... it's that big nut on the oil filter head that has a threaded screw (with a locknut) sticking out of the middle of it. Unscrew the outer nut to remove the valve assembly from the car, then note the position of the screw before removing it to disassemble the valve."

I think a stuck valve often manifests itself as low oil pressure but cleaning the relief valve can't hurt and you can easily use it to lower the pressure (that's what it's for).

FWIW - some attribute the sticking of this valve to the use of Castrol though I have never had this problem with that brand.

The dipstick symptom sounds more like crankcase pressure building up (a different problem).

Thanks for the info. I'll remove the oil pressure valve and clean it and see what happens.

Geo, I believe my problem might be abnormally high crankcase pressure as you mentioned. Do you know what causes this? My engine has been completely rebuilt and has less than 500km on it.

Does the crankcase have a pressure relief tube like the differential does on most cars? I want to say it does, but I'm not totally sure. I once saw a Ford Explorer who's front diff's pressure relief valve got clogged up, and all of a sudden it finally built up enough pressure to blow the crud out all over the front frame and suspention. After that happened there were no more problems.

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The dipstick symptom sounds more like crankcase pressure building up (a different problem).

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I would think that higher than normal oil pressure could cause more leakage around the dipstick & other places. Higher pressure means more flow & more oil flying around inside to escape wherever it can.
D

Gene--A stuck relief valve will only cause low oil pressure as more oil is bypassed directly to the sump; it will not cause higher pressure. Your pressures are consistent with mine, which reamin that way 12K miles following a rebuild. Don't fret over it.

Do you have that felt donut on your dipstick? You shouldn't have any oil blowby there. Are you getting a good carb vacuum off the valve cover?

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My oil pressure seems too high. At idle it's around 55-60psi but at 2500rpm's and over the pressure rises and stays around 80-95 psi. I also notice oil oozing from the dipstick area. Any idea what is causing the problem?


Thanks,

Gene

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probably a coincidence about oil seepage....could be a bad sending unit, replace it. Also could be a faulty reading from your gauge.

I've replaced my sending unit but haven't calibrated the gauge.

Rick, I do have the felt donut around the dipstick. As for the carb vacuum, I haven't check this (not sure how).

The reason I'm so worried is because I took my TR to get the carbs adjusted so I could pass an emission test. The mechanic said he couldn't fix the emission problem because my crankcase pressure is too high. He thinks I have a bigger problem but doesn't know why unless he "investigates" more (i.e. start taking things apart). He said my rear seals will blow if I keep driving. He also said my rings are bad, but I'm not blowing any smoke! I'm not a mechanic but something seems fishy here.

Thanks for all the help guys. Any more thoughts are appreciated.

Gene.

Hello Slider,
I have been running Triumph 2000, 2.5 sedans (same engine)for many years and have experienced high oil pressure. The first time was a stuck relief valve (Closed) and the pressure was enough to blow the seal of the oil filter. This is rare. My recently rebuilt engine had your sort of pressures which I reduced by putting another washer under the pressure relief valve cap, i.e. reducing the spring pressure.
Your breathers on the rocker cover could also be blocked, I would look at cleaning them out, or the hose could have collapsed internally. On my UK spec engines the breather has a gauze filter then connects to the air cleaner so there is no real vacuum on the breather.

Alec

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Geo, I believe my problem might be abnormally high crankcase pressure as you mentioned. Do you know what causes this? My engine has been completely rebuilt and has less than 500km on it.

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One cause is blow-by which can occur in a rebuilt engine when the rings have not seated properly. 500 Km or 300 miles is early days -- are you following a regimen of break-in style driving?

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He thinks I have a bigger problem but doesn't know why unless he "investigates" more (i.e. start taking things apart).

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Gene--Ask your mechanic to perform a leakdown test on the cylinders to confirm the worn rings theory.

Geo, I have about 500km on the rebuilt motor. I've followed all the break-in procedures. Maybe I need to put on a few more km's?

Rick, I haven't heard the term leakdown test for a while. Is that when you measure the compression, put oil in each cylinder, and then re-measure the compression again? If there is no leakdown, then the compression should rise?

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I have about 500km on the rebuilt motor. I've followed all the break-in procedures. Maybe I need to put on a few more km's?

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Did those procedures call for an 'easy break-in'? Or did they have you do a series of sudden hard accelerations followed by abrupt decelerations?

There are conflicting theories about how to break in an engine but the newer thought seems to be the latter approach: to really load the engine by using hard full-throttle acceleration & sudden deceleration to properly seat the rings.

Don't run out and try this w/o some 2nd or 3rd opinions but my personal opinion is that this is the best way to break it in (first 200 miles).

Slider,
More than you wanted to know about leak down testing:

The definitive test is the “leakdown test,” but this is much more involved than the compression test & does require a source of compressed air. This test is done with the cylinder "exactly" on TDC compression stroke. In my experience, a street engine is sour if the test shows more than 10 percent leakage and race engines are often rebuilt if leakage is more than 3 to 5 percent. The test will tell if the problem is intake valves, exhaust valves, rings, cylinder-to-cylinder head gasket leakage, or leakage into the cooling system from cracks or head gasket. A newly built race engine will often be torn down and corrected if leakage is more than 2-3 percent.

The leakdown test is also called a “differential pressure test” in the aviation industry. Piston-type aircraft engines are required to be tested in this manner and to meet certain minimum specifications.

With the commercial tester (differential pressure tester) the pressure is set with the regulator to show a readable pressure on two gages. The first gage reads the applied regulated pressure, and the second gage reads the pressure on the cylinder. For aviation there is a specific calibrated restrictor orifice for each specific engine.

Another variation is the single gage plus regulator tester which is adequate for all non aviation uses.

Basically, the tester is a flow meter that measures the amount of leakage flow in the cylinder. In addition to the leakage readings, the exact cause of the leakage can be determined by listening for air leaks. To do this use a piece of small rubber vacuum hose, and stick one end near the suspected leak and the other end in your ear.

Adjacent cylinder sparkplug holes: An air hiss heard here may indicate a blown head gasket between cylinders or it may be leakage heard through an open valve.

Exhaust pipe: An air hiss heard here may indicate a burnt or stuck exhaust valve.

Carburettor or throttle body: An air hiss heard here may indicate a bent or stuck intake valve.

Oil filler hole: An air hiss heard here may indicate broken rings, worn rings, or a damaged piston.

Radiator filler cap: Bubbles here will indicate a leaking head gasket or cracked head.

Note that a valve leak is sometimes caused by only a small piece of carbon or dirt on the valve seat. This can be corrected by carefully tapping the top of the valve stem to dislodge the carbon.
D

Gene--To add to Dave's excellent information, see https://www.mgdriversclub.com/tech/cylinder-leakdown.html. If your mechanic is reputable, he will agree with your suggestion. Or perhaps you'd enjoy getting the bits together and making your own tester.

Wow, that's a lot of information on the leak down test. It's definitely something I'd won't do myself.

Today I hooked up a vaccum gauge to the intake manifold and got a steady idle reading of 19 in Hg. Does anyone know what the reading should be? I'll borrow a compression tester this weekend and take some measurements. I hope to isolate the problem myself before I take it into a shop for repairs - if neccessary. All this great advice from everybody sure helps a TR6 rookie like me.

I think 21 or so is ideal, but it depends on your particular engine setup (valve diameter, lift, and duration). The important thing is that the reading was steady which would not be the case with worn guides. The leakdown will give you the bottom line.