View Full Version : TR2/3/3A tr3 oil pressure

12-02-2004, 02:07 PM
Hello Tr3 people I am new to the forum and I have a question on oil pressure. When I am drive my tr3 on the freeway, my oil pressure drops from the in town reading of about 55 to 70 psi (depending on temperature and conditions) to about 49 psi freeway constant. This in itself is not too frightening to me, but when I first get
off the freeway the oil pressure drops down to about 5- 10 psi! However, when I start driving in somewhat normal light traffic again, the oil pressure goes back up to say 50-65 psi-- rising accordingly with engine RPM and seems to operate normal. In other words, on long runs, at high RPM the oil pressure is low and when I first end the run it is very low! Then it returns to somewhat normal.


Dave Russell
12-02-2004, 03:13 PM
Hi George,
I think your experience is in keeping with the fact that the oil viscosity drops when the engine oil is really hot. In normal light traffic the oil cools somewhat, viscosity rises, & pressure comes up. This is to be expected, as is the fact that pressure is lower at lower rpm because oil pump output is proportional to engine rpm, whereas oil flow requirements in the engine are fairly constant with rpm. When you first get off the freeway, the oil is very hot, cooling air flow is less, & rpm/oil pump output is less, so oil viscosity & pressure are lower. You may have some engine or oil pump wear which is exagerating the changes. Not a serious problem in my estimation.

Fresh 20W50 oil & a new good filter, not Fram, may help the situation. Give it a try. Old oil usually loses some of it's viscosity from breakdown & fuel dilution. The definition of "old" depends on engine operating conditions & can vary quite a bit. Some engines under ideal conditions may require oil changes at 4000 miles, others can only go 1500.

Simon TR4a
12-02-2004, 04:02 PM
Hi George,
Mostly in agreement with Dave, see if the same happens with fresh , good quality oil; if it does consider getting an oil cooler. With a cooler my TR4a, same engine as yours, (last rebuild 1973) maintains 65-70psi.
I would offer the opinion that the oil and coolant get hottest in heavy traffic; at highway speed so much air rushes through the radiator that even though the engine is doing more work the coolant will stay in the normal temperature range without use of the fan (if you have electric fan you can easily verify this.)
I have found that synthetic oil gives lower readings on the guage because it flows more easily, perhaps this is a factor.

12-02-2004, 04:11 PM
Thanks Dave for your comment. I was hoping someone would say something with respect to oil viscosity. I am going to try the 20W50 and see what happens. I am using 20W40 and usually change the oil at about 2500 miles. One thought I had was that the gauge is old and might be fatigued. But who wants to blame an oil gauge and find out the hard way that it was not the gauge. The gauge is probably the original. Have you ever heard anything on the life expectance of one of these gauges?
Regards George

12-02-2004, 04:28 PM
Welcome to the forum -- good to see another Washingtonian on here (where are you in WA?)

When I lived in Houston, I used to use straight-50WT racing oil in my '59 TR3. It makes a big difference in the hot climate -- although I wouldn't recommend it if you're using your TR year-round in WA...but in the summers, it's a good one.

20W50 should suffice for the winter.

12-02-2004, 05:28 PM
Hi Sam thanks for your comment. I am going to try 50w in the summer. I live up in Tacoma and usually drive this car about five times a week. The car is a small mouth BRG you might have seen me. However, I usually do not drive on the freeway, but I have thinking about some road trips so I am just trying to get my ducks in a row. Anyways, I will probably need to take a cell phone.


Geo Hahn
12-02-2004, 07:22 PM
Regarding the gauge -- possible but not likely to be at fault. They seem to last indefinitely though I have never checked one to see how accurate they are. The variations you are seeing at different running conditions sound like the gauge is fine.

Dave Russell
12-02-2004, 08:25 PM
Hi George,
I would offer the opinion that the oil and coolant get hottest in heavy traffic; at highway speed so much air rushes through the radiator that even though the engine is doing more work the coolant will stay in the normal temperature range without use of the fan (if you have electric fan you can easily verify this.)

[/ QUOTE ]
Hi Simon,
You are quite correct about the coolant temp. However, the oil does not benefit nearly as much from increased air flow, unless of course you have an oil cooler in the increased air flow. The oil containing part of the engine has very little surface area to dissipate heat from. For example, the coolant may have 25 times as much surface area exposed to air flow as the oil does. From my observance of oil temp. gages, the oil runs much cooler under light around town load conditions than it does on the highway.

12-02-2004, 08:39 PM
I don't know about TR3s in particular, but most cars have an oil pressure relief valve that opens when the oil is cold and the pressure gets very high, to prevent the high pressure from blowing seals. I used to have an XK150 that would lose oil pressure on the highway when the oil pressure relief valve would stick open. IIRC, it was in the base of the filter housing. I'd pull it out, wiggle it around, and it would be fine again.

Pressures that low on the hwy would scare the cr*p out of me. /ubbthreads/images/graemlins/eek.gif

12-03-2004, 12:23 AM
George, Eric is quite close on this (I think). Remove the relief valve assy from the oil filter head, Its likely the spring is bad and may need to be replaced. This is very easy to do. When its fresh and clean, put it in and set the oilpressure to factory specs(60 to 70psi @ 3000rpm hot). If your idle pressures get too low ,its likely the lower end is to blame. But dont worry, with good clean 50wt a weak set of bearings can last for years,just adjust the oil pressure relief valve to compensate as time passes.But dont over do it, extreme pressures on cold start will blow out the gage in dramatic fashion!!!!!
MD(mad dog)

12-03-2004, 01:12 AM
I agree that it would be a good idea to check the pressure relief valve which is in the oil filter head on the side of the block. Idealy, it would be best to check with a separate, accurate pressure gauge, but the one in the car can be used if that's the only one available. In my experience, these gauges seem to last forever. The weakest part of the gauge are the seals on the line.

I'd like to add that if you decide to install an oil cooler, it really should have a thermostat to prevent over-cooling the oil. Oil needs to reach a certain temp to remove condensation and other contaminants. I recently saw an oil cooler takeoff that incorporates a built-in thermostat at Racerpartswholesale.com and am planning to try one on my TR4. If your car has the original oil filter, an adapter for a screw on filter is needed, then the oil cooler takeoff attaches to that. The screw on oil filter is attached to the takeoff (sometimes also called a sandwich plate, for obvious reasons).

A ten or thirteen row oil cooler is generally adequate for our cars. I don't recommend the kits sold by the "big three" TR mail order parts houses. It's nothing more than a standard Mocal that's available for a lot less elsewhere, and the stainless steel braided hoses included with the kit at pretty short, seriously limiting mounting options. I haven't tried the kit with the rubber hoses, so can't compare. Still, I think the whole thing could be put together for a lot less that the kits sold by the major TR vendors.


Simon TR4a
12-03-2004, 10:41 AM
Lot's of good advice on this board!
I agree (again) with the above, Dave finished off the thought for me; if you've been in a car with separate oil temp and coolant temp gauges the oil does get hotter on the highway for the reason he states.
I would rather use an oil cooler to control temperature than use a thicker oil or adjust the pressure relief setting.While these are tough and low-revving engines, these measures are really a short term way of masking the symptom.


ron wilson
12-03-2004, 02:49 PM
someone mentioned to use a good oil filter (not Fram) what do you suggest and what is it about fram yu do not like?

Rick O.
12-03-2004, 04:15 PM
what do you suggest and what is it about fram yu do not like?

[/ QUOTE ]
If you're a Wal Mart lurker, go for the Super Tech filters at $2 (excellent quality). Other favorites are Motorcraft, Purolator PureOne, and anything from Champion Labs (Wix, Napa). I can make these recommendations because I spent more time than I care to admit here: https://theoildrop.server101.com/cgi/ultimatebb.cgi

After going there, it will quickly become evident why the orange can filter is not the wisest selection.

12-04-2004, 08:18 AM
I have a healey with a low oil pressure problem. The prerssure relief piece might be the cause if you have one on the triumph engine. Not sure about that. I have included a link about the healey engine oil pressure problem. 2 of them. one from this site and one externally. good luck


https://www.britishcarforum.com/ubbthread...=true#Post91478 (https://www.britishcarforum.com/ubbthreads/showflat.php?Cat=0&Board=UBB1&Number=91478&Searchp age=1&Main=89145&Words=oil+pressure&topic=&Search= true#Post91478)

Good Luck