Low oil pressure worries
Posted 30 July 2018 - 09:14 PM
I have noticed the following oil pressure behavior on my 65 TR4A, over the 2 years Ive owned it. At start up, the pressure reads 50. As I drive and the engine heats up, the pressure will drop and rise in widening ranges as Im off and on the gas.
For example, after driving a half hour or so, at a stop, the pressure may drop to 20, then climb to 45-50 if I give it the gas, dropping to 40 as I cruise. However after driving an hour or so, the pressure will drop to 10 at idle! Returning to 40 or so at cruise, and not quite 50 under load.
In case the dash oil gauge was inaccurate, I purchased an after market one, swapped it in temporarily, and saw similar readings.
However the car has always run great, no smoke, no oily messes, dipstick levels are good. The plugs are tan, with no indication of oil fouling.
I did a compression test and here are the numbers:
1 - 150
2 - 160
3 - 165
4 - 160
Since #1 was lower than the others, I squirted a little oil in and ran that one again. It then showed 160. I assume from the results that #1 has some blowby around the rings, correct?
That 10 reading makes me a little concerned Im driving a hand grenade, but the car sure scoots along happily enough. BTW, no odd noises from the motor, and I do not know the motors history before I got it.
Posted 30 July 2018 - 09:35 PM
I would not be concerned with any of those figures. OK, a little wear on #1 cyl but certainly nothing to worry about, oil pressure is fine.
Overseas (Ex Cleveland Group member)
Old English Car Club http://oecc.ca/cib/
1966 New White TR4A
1968 New White TR250 (under restoration)
Posted 30 July 2018 - 09:47 PM
I think those oil pressure numbers are quite normal for an engine with some miles on it. The TR engine has large bearings which spread the load and will go on for many years with low oil pressures at hot idle. What you could do is adjust the oil pressure relief valve on the filter head/block to increase the pressure to ~70 on a cold engine at 2000rpm...that probably won't make much difference to hot idle, but just exploits the adjustment to get a higher pressure under load.
The compressions look fine, No1 slightly low...could be wear but could also be lack of use (stuck ring) ...might fix itself after some exercise...
From you description it's time to enjoy the car through the rest of the summer!
'67 Triumph TR4A, '68 Rolls Royce Silver Shadow, '73 Jaguar E-Type V12, '73 BMW 2002 Tii Alpina, '85 Alfa Spider, '03 Lotus Elise
Posted 30 July 2018 - 09:47 PM
If you would like to see a little more pressure then try a different oil eg
Millers, Penrite among others.
Edited by potts4a, 30 July 2018 - 09:50 PM.
Posted 31 July 2018 - 09:40 AM
As all have said your compressions are good and show a healthy top end. Concerning the oil pressure, low but do not overly concern yourself. I would do 2 things, firstly put a mineral 20-50 oil in, then remove the oil pressure regulator and give it a thorough clean. It is just by the oil filter housing and very easy to access. Reassemble and turn up the pressure by loosening the lock nut and turning the screw head clockwise. If this does not bring the pressure up buy a new spring and ball for the regulator and try again. If the oil pressure has not gone up then you have worn big end/main bearings. However, as people have said, unless you are going do a 24 hour Le Mans race just live with it.
Posted 31 July 2018 - 10:22 AM
You don't say what oil you are running currently ?
That can make a difference to our engines, as previously said a mineral 20-50 will work fine, don't get sucked into the "racing oils" "synthetics are best" scene, costs you more money for no gain worthwhile.
When I bought my TR it had 20lbs pressure at 50mph and I ran it like that for a year whilst I got round to it, it used to blow a little oil mist out of the exhaust but drove well and without any noises. Then I took the PRV (pressure relief valve) apart and found a small lump of carbon big enough to be a diamond under the large ball bearing holding the spring slightly open. Cleaned everything out and reassembled and the oil was back up to 70lbs running. Try cleaning that area first as previously pointed out, easy to do, and you can replace the spring if you want for small change.
As for the compression test, not teaching you how to suck eggs but many people don't realise that it needs to be done with the carb pistons lifted as you do it and the numbers you get don't mean too much unless they are seriously low or different from one another.
Your number 1 cylinder at 10lbs down is only 6% less than the others...get my drift ?...peanuts and when you say
"Since #1 was lower than the others, I squirted a little oil in and ran that one again. It then showed 160 "
I take that to mean you ONLY oiled number 1 cylinder and tested that (otherwise why just test that one ?) whereas if you had oiled ALL cylinders you would have seen ALL cylinders improve their compressions by a similar amount, figures in the range you report wouldn't cause me to lose sleep.
I take it you are running with air filters and not straight trumpets on the carbs ? on the race engines we built I'd often find any variation in compression would happen with the cylinders 1 and 2 which I put down to "dirty" air being fed into the whilst racing (no filters mean lots of grit laded air being sucked in to them before it had a chance to reach the rear 2 cylinders...yes I know the firing sequence).
Buy a flat cap or WW2 flying helmet and take the TR out, a great summer for using them.
Posted 31 July 2018 - 01:01 PM
However I will respond to some of the questions.
First, several of you mentioned the oil pressure regulator. I forgot to mention that I did take apart and clean the oil pressure regulator over the winter. Didnt find anything amiss, though I did not do any adjusting of the valve. BTW I also have a spin on type oil filter and adapter, if that matters versus the stock cartridge type.
These are to Micks queries. I did not realize that the SU pistons had to be raised during the compression test, so thank you for that info. However I did have the butterflies wide open. I did expect that oiling the other cylinders would raise compression across the board, however I only oiled #1 to see if the rings or valves were suspect, thinking that if it was a valve I wouldnt see much, if any, change. And finally, I do have a flat cap!!
Oh I forgot to answer regarding the oil I use. Im using Valvoline VR-1 20w50 oil. It has a higher ZDDP content than most available oils around here. From reading US based British car forums, it seems to be the oil of choice.
Edited by Tr4aJim, 31 July 2018 - 01:08 PM.
Posted 01 August 2018 - 12:43 PM
You know where the oil pressure regulator valve is so start by adjusting up (clockwise) about 1/3 of a turn to begin with. It only takes a couple of minutes. Let is know the result.
Posted 02 August 2018 - 08:46 AM
You mentioned you had a spin on filter adaptor. A friend of mine had one (not on a TR) and suffered from low oil pressure. He even had the engine rebuilt but it did not cure the problem. The problem was finally traced to the adaptor not mating properly with the engine structure. You will read loads of tales of woe on this forum about TR problems and a high % are problems caused by modifications. May be worth pulling off the adaptor and refitting with new gaskets and o rings (I do not know what would be fitted). IMO worth a try
Posted 05 August 2018 - 09:44 PM
Posted 07 August 2018 - 10:35 AM
Unless this is a case of wheel tappers syndrome it is beginning to look like a worn bottom end but worthwhile trying to get hold of a know serviceable gauge.
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