TR6 TR6 High Oil Pressure

[bunzil]

The oil pressure in my 76 TR6 has suddenly increased to around 65/75 lbs at cold idle. I installed a new relief valve and standard spring but with no change. The gauge returns smoothly to zero when the engine is turned off.

Any suggestions?

As always, thanks.

 

[charleyf]

The cold idle is always higher than a warm idle. So what is the pressure at the warmed up idle? This will be what really counts.
Charley

 

[poolboy]

I understand your concern is what you say was 'suddenly' an increase in OP. I can't explain that, but maybe this will ease your mind:

In the Summer, my OP gauge needle almost pegs at the first start up of the day while the engine is idling.
It doesn't change much until the temperature gauge starts to move and that's my cue to put the transmission in gear and drive off...slowly at first. By the time the coolant is at Normal Operating Temperature according to the gauge, which is about 3 miles further, the OP has dropped a bit more, enough to drive 'normally'
It takes at least 20 minutes of normal driving before idle OP is able to come down to 25 psi.

 

[charleyf]

So the next question is -- Do you trust your gauge?
I tried three different gauges on a TR4 once and got rather different readings. Not grossly different but different enough to realize that some are just low and others on the high side. The one thing that I did notice is that one of the gauges seemed very sticky. In that the needle seemed to stick in position for some time before it went down. Again the gauge is how old?
Charley

 

[bunzil]

So the next question is -- Do you trust your gauge?
I tried three different gauges on a TR4 once and got rather different readings. Not grossly different but different enough to realize that some are just low and others on the high side. The one thing that I did notice is that one of the gauges seemed very sticky. In that the needle seemed to stick in position for some time before it went down. Again the gauge is how old?
Charley

Thanks for your responses. I trust the gauge but admittedly it is original, 40years old. I've been giving this some thought and will check it a bit more with a fully warmed engine. It may just be, sorry, that my recollection of "normal PSI" for my engine was fully warmed, not cold. In other words I may have misread the issue. As stated, idle is one thing, hot is another. I'll check. Thanks again.

 

[bunzil]

Circling back to the matter of an increase in oil pressure:

1) I was lent a known accurate gauge and it read identically to mine. As a base, I selected cold idle with the choke out to establish 1,000 rpm, both gauges read just over 75 psi at cold.
2) Idle at full hot is around 35 to 40 psi.
3) The manual states between 40 and 60 at 2,000 rpm (hot). I'm running at 75.
4) The rocker arm seems to be weeping normally, all of the tappets are swimming in oil.
5) I've replaced the spring and pres. relief valve.
6) The only other change is I switched over to a Wix filter last fall after being told my time honored Fram PH3600 was inferior. But the change of a filter shouldn't be the cause.

If the car had always been this way I wouldn't be concerned. But this is a recent change, although I can't tell when it happened.
Anyone have any crazy ideas?

Thanks

 

[poolboy]

Replace the WIX with a FRAM TG3600 and see what the OP looks like after the motor oil is 1000 miles old. OR if it really concerns you, switch to a different viscosity motor oil.

 

[bunzil]

Replace the WIX with a FRAM TG3600 and see what the OP looks like after the motor oil is 1000 miles old. OR if it really concerns you, switch to a different viscosity motor oil.

The viscosity has been 20-50 for years. As the Wix is a variable I'll try that, although I wouldn't have thought the filter to make much of a difference.
I'll report back.

 

[pa297pass]

I don't remember the specific numbers, but I remember getting an noticeable increase in oil pressure on the gauge when I switched from a FRAM PH3600 to a WIX / Napa Gold equivalent.

This is on a non-rebuilt engine with ~100K on it.

Matt

 

[tdskip]

Absent a trusted mechanical gauge, you are going to be guessing if this is super critical to have an answer to...

 

[bunzil]

Absent a trusted mechanical gauge, you are going to be guessing if this is super critical to have an answer to...

1) I tried a trusted and known accurate gauge, lent to me from for this purpose from firm that has a firm reputation working on only British cars - it matches mine. I firmly believe it's not the gauge.
2) Changed the Wix filter back to the Fram PH3600. No change. Cold at 1,000 rpm the engine it hitting just over 75 psi.
3) Viscosity should not be an issue. I've run 20-50 in this engine for 30 yrs.

I've received an overall response of "why worry about it?" which is difficult to accept. When a constant suddenly changes, isn't that worth questioning?

 

[poolboy]

75 psi cold at 1000 rpms sounds low compared to my engine when it's waking up for the day..mine would be just about pegged at 1000 rpms cold.

 

[smaceng]

I second the "why worry about it" . So it is a little high maybe....what are you going to do, tear the engine apart and put in worn bearings? Put in a worn oil pump? OK, I know it is your problem, and you are OK to worry about whatever you want. As a guy who has just started a car and driven it around the block for the first time in 11 years, I had a lot more things to worry about than high oil pressure.
Cheers, good luck
Scott in CA

 

[pdplot]

Just a thought. What would a partially-plugged oil gallery do to the pressure?

 

[bunzil]

Just a thought. What would a partially-plugged oil gallery do to the pressure?

Yes, a partially plugged oil galley would cause increased pressure, and that's part of my concern since it seems I've exhausted every other option. But that raises it's own conundrum; endure the cost of ripping it apart in search of something that is potentially not there, or wait until it manifests itself and then deal with the cost?

The reasoning of the moment would indicate to leave it alone and keep an eye on it. Thanks.

 

[Popeye]

Just to be clear that we are all understanding the problem correctly: the oil pressure has made a step change to a high value at cold idle. At other operating conditions the oil pressure is identical to previously. (Hot idle, running at speed, etc.)

Did any event coincide with this change? You mentioned changing oil filter brands - did the oil pressure change coincide? Did the brand of oil change at this point? Realizing the weight is the same. Different brands could use different additives to achieve the reasonably constant viscosity across the temperature range. I'm not an expert in this area, so take this with a grain of salt - but I ask why would oil pressure change only at one operating condition and not others?

 

[bunzil]

Just to be clear that we are all understanding the problem correctly: the oil pressure has made a step change to a high value at cold idle. At other operating conditions the oil pressure is identical to previously. (Hot idle, running at speed, etc.)

Did any event coincide with this change? You mentioned changing oil filter brands - did the oil pressure change coincide? Did the brand of oil change at this point? Realizing the weight is the same. Different brands could use different additives to achieve the reasonably constant viscosity across the temperature range. I'm not an expert in this area, so take this with a grain of salt - but I ask why would oil pressure change only at one operating condition and not others?

Thanks Mike.

Your questions are really where I was coming from: what would warrant an unexpected change (upwards) if everything else had remained the same?

I ran it 80 miles today in 80 degree temps and, FULLY hot, the numbers are seemingly not as ominous as could be. I am going to take everyone's advice and sit back and keep an eye on it.

Thanks to all. I hope I didn't drive everyone nuts.

 

[dencar 1938]

So the next question is -- Do you trust your gauge?
I tried three different gauges on a TR4 once and got rather different readings. Not grossly different but different enough to realize that some are just low and others on the high side. The one thing that I did notice is that one of the gauges seemed very sticky. In that the needle seemed to stick in position for some time before it went down. Again the gauge is how old?
Charley

Charley:
I have a1973 TR-6 and I'm having some oil pressure problems, I'm using joy Gibbs 15-50 with zinc been using it since the rebuild about 4 years ago. I have replace the oil pump and the pressure value on the side if the engine. As I start the car the oil pressure goes to about 45-50 lbs on the gauge, after I drive it for a period of time the pressure goes to about the middle of the gauge, but after a longer trip it drops to about 20 lbs , come to a stop and it goes below that. But after I start moving again it goes back up to about 25 no more. Before all the repairs driving a long time the oil pressure never dropped below the middle of the gauge. Do you have any suggest of what might be going on I with it???

 

[charleyf]

Charley:
I have a1973 TR-6 and I'm having some oil pressure problems, I'm using joy Gibbs 15-50 with zinc been using it since the rebuild about 4 years ago. I have replace the oil pump and the pressure value on the side if the engine. As I start the car the oil pressure goes to about 45-50 lbs on the gauge, after I drive it for a period of time the pressure goes to about the middle of the gauge, but after a longer trip it drops to about 20 lbs , come to a stop and it goes below that. But after I start moving again it goes back up to about 25 no more. Before all the repairs driving a long time the oil pressure never dropped below the middle of the gauge. Do you have any suggest of what might be going on I with it???

I am not familiar with the TR6 pressure valve. On the TR3-4 engine the pressure can be adjusted. So when you put in the new pressure valve was there an option to adjust the pressure. If your lower readings started after that replacement , I would look there first. Are you getting good oil quantity and pressure to the top (lifters)? Then gauge problem? With your recent rebuild, the last thought would be worn bearings- not likely.
Charley

 

[auprichard]

As Charley says, the oil pressure can be adjusted on the TR3/TR4 engines. The 6-cylinder engines are not adjustible BUT there are two different springs which can be used inside the pressure relief valve. An old trick to raise oil pressure was to stretch the spring a little). SO:

To the original poster (Bunzil) - my bet is that you replaced the spring with the longer version. In which case everything makes sense and you are fine. If you don't like the change, fit the shorter spring.

To Dencar 1938 - the rule of thumb is 60 psi at 3000 rpm. 20 - 25 lbs of pressure is fine at idle but not when driving. Similarly, 45 at cold start-up is low. Is it possible that your problem is the opposite of the original poster's? That you replaced the spring with a shorter one?