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TR2/3/3A very low oil pressure when TR3a is warmed up

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2billydavies

2billydavies

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Hi everyone.... just wanted to bounce something off of you all, maybe you can help.
My TR3a runs perfectly (finally) and I really don't have any issues at all anymore. But the oil pressure concerns me a bit, and for the life of me I can't remember if it was doing this
before I did my engine rebuild. I don't recall it... but that was 2 years ago since my rebuild.

Basically, the oil pressure drops to almost 0 when the car is completely warmed up. Once started, it easily pushes past 50 on the gauge (original gauge, original lines, etc).
For the first 10 minutes, it fluctuates between 30 and 50.... sometimes a little higher if i'm under load and getting up to speed.

However, once completely warmed up to running temperature.... the oil pressure just drops like a brick. Sometimes it's so close to zero I want to pull over.

It sounds fine. It runs great.... but why does it do this? Is the engine getting any oil? That's my concern. I keep thinking its the grade of oil I use.... which is 10W30. I live in Florida, so its
warm all year round.

When I did the engine rebuild, I inspected the oil pump. Absolutely nothing looked out of whack... quite honestly it looked brand new. Could I be missing something?
Thanks for any input ya'll might have!
Billy
 
Sure sounds like something got overlooked. Cam bearings changed? Rod & main clearances checked? Bushing for the oil pump shaft? Did the old bearings look oil-starved?

10W30 should be OK this time of year. Is the problem the same right after you change the oil? Have you tried heavier oil to see what happens?

Have you tried a different oil pressure gauge? What happens if you loosen a fitting (like the banjo at the oil filter head) with the engine hot?

Normally, my suggestion is to leave the oil pressure relief valve alone, but if you have verified the lack of oil pressure, it's probably worth pulling the valve apart to be sure the spring isn't broken, no FOD in the valve seat or damage to the ball, etc.

BTW, an old worn out engine (like mine) will clatter with no oil pressure, but a nice fresh engine won't. It will run just fine, right up until you hear that awful screech of a welded bearing. IMO anything less than 10 psi per 1000 rpm is time to call a flatbed.
 
Could be the oil bypass valve is stuck open. After that, it's gotta be internal...so long as your gage is connected and reading properly.
 
hmmm...... i'm going to start checking all of those you listed. I have not tried any different oil gauge at all. it's the original, I thought it was working OK but im really starting to wonder. Yes, it did the same thing after an oil change. I just did that about two weeks ago hoping for different results, but here I am. I was thinking that maybe I need to try a different weight of oil but everyone I've talked told me 10W30 is fine and that's what a ton of people use.

I'm going to take a look at all of your suggestions. I'm finding it hard to believe this thing is pumping oil around.... or it just stops when the car is warmed up (which is why i keep thinking maybe I need a heavier oil). But I can tell you one thing for certain: i'm not interested in rebuilding this engine again right at the moment. lol. thanks a ton guys... gonna get back under the hood.
 
Check to make sure your distributor is installed properly and that it is all the way down in its clamping mechanism.

Cheers
Tush
 
What type of filter are you using. If it is adapted to a spin on, might try a different filter, as the bypass could be stuck.
 
LarryK said:
What type of filter are you using. If it is adapted to a spin on, might try a different filter, as the bypass could be stuck.
Click to expand...
I'm using a FRAM spin-on. It's pretty much been the same filter/adapter for the past 25 years. When you say oil bypass, what exactly are you referring to? I just drove it 20 miles round trip to my daughter's soccer practice. Ran absolutely perfectly... but the oil pressure is really scaring me. It hovered right around 10 psi (first line on the original gauge after 0). When I give it gas, it slowly raises but never went past 30psi.... I"m going to park her and take a look at all of your suggestions above. The distributor is definitely in all the way and the little key on the end of it is in correctly. Other than that, I guess i'll start with all of the suggestions above. Does anyone have any suggestions on a heavier weight motor oil? I'm using 10W30 now.... I know the manual says something like 20W50 (or something like that) but at the Auto Zone near me that's motorcycle oil. Is that the same thing?? (clearly not an oil expert here, lo). Anyways, thanks everyone. This car wouldn't even be running if it weren't for this forum.
 
Do you have an external cylinder oil feed line on the car, if yes try it with it off.
 
Autozone should have Valvoline VR1 "racing" oil in 20W50, which is a good choice IMO. (Also what I use in my TR3.) It has the higher level of ZDDP, which many say is important for our old flat tappet engines.

But the owners manual calls for 30 weight at temps to 70F, and only 40 weight above that. So the 20W50 shouldn't be needed unless the engine is well worn.

If the bypass valve in the spin-on were stuck closed, and the filter was clogged, then the bypass in the filter head would open. Borders on impossible for either of them to stick closed, let alone both of them, unless you've been using superglue instead of oil.

But, the gauge pickup is on the inlet side anyway, so it would still show pressure even if both valves were stuck and the engine being starved.
 
The fram filters have a built in by-pass. Try putting another filter on or a different brand. This is since your last change. Filter $5, engine $2K. I have o be careful of brand dissing but have had this numerous times, now I use a Wix or Mann or Cooper. Just sayin!
 
50W oil will raise the pressure...but 30w in a newly rebuilt motor should not result in pressure that low. In a well worn motor 50W will bring the pressure back up until a rebuild. You have something else going on, though.
 
Hi Billy,

I can understand your concern and desire to address this. You have spent a lot of time and money getting to this point.

My suggestion is that you need to take a closer look at the oil pump. Remember that pressure is essentially the result of resistance to flow. If you do not have good flow you will not develop pressure.

Your description states that you have acceptable pressure when things are cold but it drops significantly when warm.

In your original post you stated that you inspected the oil pump and everything looked fine.
  • Did your measure the 3 key clearances (inner to outer rotor, rotor to housing, and rotor end clearance)?
  • Were there any wear patterns on the end plate?
  • Was a gasket used when the pump was re-installed?

My experience is that pump clearances are critical. Larger clearances allow oil to bypass within the pump especially after the oil has thinned as it gets hotter. Pump performance will drop even as clearances wear the upper limits.

Think of this example. In a TR4 the maximum allowable rotor end clearance is 004". If the actual clearance is .006" the area open to allow end rotor bypass has increase 50%! In the world of hydraulic pumps that can be a big difference. Add to this that the other clearances will probably be as worn and there is a lot of opportunity for bypass in the pump.

I know it is a pain getting to the oil pump on an installed engine but the cost of not doing it can be worse.

Good luck and keep us posted.

Rusty
 
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