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Triumph TR6 - TR6 Low oil pressure

Just rebuilt my 73 TR6 engine. Realized when I opened the engine that it has been rebuilt before. There was no play or wear the bottom part of the engine so I put same size but new bearings and put back the same trust washers. Play was minimal.

When car is hot, when I start it pressure goes around 50 and after 1 min of running drops to 10 and do not go back when I accelerate.

What can this be? Oil pump seams to be within tolerance? I found a loose valve/rocker? Oil is not very visquous?

Please help

Yvan

Yvan

It's possible you need a new oil pressure relief valve (& spring) if that has not been changed out. The valve "plunger" can be worn over time and not seal well.

Brent
Brent B

Yvan:

Oil weight? Had similar problem using 10W30. Completely cured with 20W50.

Keith
Keith

Mine's a 1974 1/2 with 110,000 miles on the clock. No idea if it has ever been rebuilt. It runs great - no strange noises - a little bit of ticking but nothing that really causes alarm.

I'm having low oil pressure problems too. At cold start-up I get 75 lbs. Once warm it idles at about 15 lbs. At 100 KMH/60 MPH in overdrive it sits at 25lbs. The needle will go up and down as I blip the throttle so I am assuming the guage is not faulty.

I spoke to my local mechanic/expert regarding the possibility that the PRV was the culprit. He doesn't think it is. However based on what I have read here previously, I have decided to replace it as the piston shows some evidence of scoring. I had to order the part and won't have it until early next week. I'll let you know if my problem clears.
Moe Blakey

I think even although the gauge goes up and down it's worth checking the pressure with a gauge of known accuracy.
Ron
R. Algie

Yvan,

You didn't mention anything about measuring the bearing to crank clearance? Did you use Plastigage to check the clearance? If you didn't do a check and don't know the actual clearance then it's possible that the crank had been re-ground.

I would check the pressure releif valve and change oil to 20w50 (both suggested above) since they are both easy to do. If that doesn't help then you can pull the oil pan and do a clearance check from underneath using plasitgage. The clearance should be no greater than .003 inches. If the plastigage does not squish at all when you torque the caps then the crank was probably re-ground and you could try new bearings that are .010 under and re-check with the plastigage.

Let us know what you find.

Henry
HP Henry Patterson

Yvan,

The pressure relief valve is cheap and easy to change. Start there and you may get lucky. My issue was a very worn springon the valve along with a scored valve that had a tendency to stick. My symptom was low pressure which divebombed to about 15 when the valve stuck. Swapping it brought it up quite a bit.

As long as I'm not hearing a knock and the pressure is reasonable, I'm not going to be concerned. Most will tell you pressure pressures are 70+ at cruise. Mine is around 40-50. To put things into perspective, by new Honda runs at less then half that.

I'll throw this out to the rest of the guys. Is my thinking acceptable in your minds? Decent but not "out of the factory new" pressure and no obvious symptoms - would you let things go?

Just wondering.

Thanks,

Don from Jersey
Don from Jersey

Don,

I believe you are correct. I could claim that my pressure is at 70 psi at cruise because it is for quite a while after starting out. However after alot of driving it becomes more in the 50 to 60 range at 2000 RPM. If I rev it up from there I can get the gage to hit close to 70 but it will settle back to about 50 as soon as I go back to 2000 RPM for cruise.
My worst case idle is about 25 psi. The Triumph owners manual spec's the pressure to 40 to 60 at cruise hot. They don't spec an idle pressure.

For another perspective.... The owners manual for my boat, which has an inboard V8, spec's the pressure to be 30 to 50 PSI at 2000 RPM. The idle spec is for the pressure to be greater than 4 psi. They spec a high viscosity oil as well.

So your philosophy of don't worry if the gage is reasonable is a good one in my opinion. Remember most cars have an "idiot" light instead of a gage that are calibrated to light when the oil pressure is in the low single digits. Not that that is good but... nobody worry's about their oil pressure.

HP Henry Patterson

Thanks for the help, Did some work and still no good.

Removed the sump to look for bearing clearance to solve my low oil pressure problem. I saw some metal dust (gray) under the #2 lifter. Didn't care too much, clearance was 0.0025"where cylinder attach, I put new oil in there, reajusted the #2 rocker that kept desajusting and went for a ride.

It took 30 seconds and the #2 lifter lost its bottom and the pushrod is now floating directly on the camshaft. Big ratteling.

What can cause a lifter to be buffed and break that way? It seems that there is not as much lubrication on the front of the header compared to the rear. Can it be related to my low oil pressure problem? Dis that cause the lifter to blow?

Please help

Yvan
YH Yvan

This may not help Yvan - especially given his pushrod problem, but there is a little known cause for low oil pressure in a TR6 that's easy to fix - if the cause applies to you.

Quite a while back - when I bought my TR6 (which had a rebuilt engine), I put on a spin-on oil filter adaptor and immediately thereafter suffered from low and declining pressure when the engine was hot. Low in my case meant 30 PSI at 3000 RPM and 5 PSI at idle after about an hour on the highway. I pulled off the bottom end of my engine to no avail. The bearing clearances were perfect and the low pressure persisted.

About a year ago, there was a post on the Triumph Mailing List describing how Castrol GTX could cause low oil pressure - just like mine. Apparently, Castrol leaves a film on the Pressure Relief Value that causes it to seat poorly. The cure is easy. Remove the PRV and soak it in laquer thinner and then reinstall the PRV. I thought there might be something to this since I've consistently used Castrol GTX since I installed the spin-on filter.

To my complete surprise, the laquer thinner application did work and for the first time in years, I now have normal oil pressure in my Six (50 PSI or higher at 3000 RPM and 25 PSI at idle after that hour on the highway).

So, I'm not sure if I've helped Yvan, but if you're using Castrol GTX and are suffering from overly low oil pressure when hot, try the laquer thinner cure. And - I now avoid Castrol and use other high quality motor oils.

PS: TR6 engines are quite robust - after 10 years of driving with this low oil pressure - I (or my engine) has suffered no ill effects.

PPS: Always check your oil pressure gauge first if your readings are low.
Brian

Interesting. I had castrol GTX inthere. I changed it today with 15W50 and then my cam follower damage occured so I could not test further. Have any Idea why a cam follower may Quickly wear and loose its bottom?

Thanks
Yvan

YH Yvan

Yvan - Did you recently change one, or all the valve lifters ? For a long time, there have been reports of the replacement lifters not being hardened. Since they are left soft, they wear rapidly.

Don Elliott, Original Owner, 1958 TR3A
http://mysite.wanadoo-members.co.uk/trebor/don3a_big.JPG
Don Elliott

Sorry to hear about your misfortune. I suspect the parts were not up to original quality. I hope it doesn't delay your driving the 6 for too long. The above posts will have me smelling like lacquer thinner soon.

How about pressure that's too high? I think I'll clean the valve and then check the guage if that doesn't help. But the bearings aren't complaining..better than low, I guess.
Tom

Yvan,

There is alot that we don't know about your engine such as: Did all this happen during the initial start after the rebuild? If not then how many miles since your rebuild? How long has the oil pressure been low? Did you put a new cam and lifters in with cam lube and break in procedure, etc... So, it's very difficult to help you pin-point a problem.

Something you may want to think about based on what you have told us:

The cam and followers get most of their lubrication from the oil thrown around by the crank. If the engine is dumping oil somewhere, resulting in your low oil pressure, and the crank pins are not getting enough oil then you may not have much oil splashing on your cam. The oil must be dumping somewhere since you are getting 10 psi hot regardless of rpm. That could be the cause of the failed lifter (and lobe?). If you don't see a huge puddle of oil on the ground and your rod and main bearings have the proper clearance and your oil pump is good then you possible do have an issue with the pressure relief valve, as mentioned, and maybe that led to the lifter failure. The lifters may also have trouble spinning in their bores if not enough oil is being sent to the top of the engine through the rocker shaft.

That is just one possible scenario. You could have two independent failures from some bad parts.

I know this doesn't solve your problem but it may help in getting to the cause

Good luck and keep us informed

Henry
HP Henry Patterson

Beautiful Sunday. I removed my header to get access to the borken #2 lifter. No more bottom and it is stuck in the hole. All others seems fine even if it seems that there is more oil on the rear of the header. First 8 lifters are saoking of oil.

I'll get the sump out (again) to recover the damaged lifter pieces.

YH

YH Yvan

Well, I installed my new PRV with a heavy duty spring. It improved the pressure a bit - now at 15 to 20 when hot idling and 25 or so when running at speed. I'll check the accuracy of the guage next.

It still runs and sounds great.

Moe
Moe Blakey

Moe,

Mine was just about identical to yours in oil pressure readings before my rebuild. I found my rod and main bearings were just about worn out. They were the original bearings and were worn into the copper. The crank also had some scoring that I had reground to .010 off. My oil pressure is off.

In all honesty, for the little driving I do with this car I probably could have let it go for a long time. My crank endplay was still pretty good even with the 100,000 plus miles on the engine.

I hope all works out for you. Who knows maybe your gage is off a bit.

Henry

HP Henry Patterson

I agree with Henry..the biggest culprit for low oil pressure is the main and rod bearings, replace them at the same time with new thrust washers a new oil pump and it will make a world of difference.
Cheers
Charlie
Charlie B.


In my last post above I said my pressure is off. I think I had a couple of beers when I entered that. I meant to say it is right on after the rebuild. It better be after all that time I spent on it.

Moe,

If you find you have to start looking into your rods and mains there is alot you can do from underneath. If your crank does not need to be re-ground then you can do what Charlie suggests from underneath. Just ask alot of questions here.

Henry
HP Henry Patterson

Hi everyone. Tought I'd keep you posted about my findings. After 2 days of work looking for main bearings clearances (they were all .015") I finally looked at the easiest thing called "oil pressure relief valve".

I put a nut as spacer to tighten the spring...Now 75 psi at 3000 and 40-50 at idle. What a miracle.

I'll replace that nut for the right spring but it's no more urgent cause it's running great.

Thanks for your help. I should have listened quicker.

Yvan
YH Yvan

Wow...you lucked out.

Before my rebuild I tried basically the same thing but rather than a spacer I stretched the spring. For me the only thing that brought my pressure back up was the rebuild. As I mentioned, my crank was scored and needed re-grinding.

By the way... when I was trying the spring thing I found that Moss sells a replacement spring that is longer than the original and provides more force to the bypass valve. They sell it for those with low oil pressure. It didn't work for me but it may for you.

Henry
HP Henry Patterson

This thread was discussed between 22/07/2005 and 03/08/2005

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