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 Posted: 06-27-2019 08:50 pm
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flatlanderep
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About 2 months ago, I had a valve clearance problem fixed by a British car shop. Now I have developed a new problem, low oil pressure, after driving less than 100 miles after getting the car back from the shop. After the driving the car for about 10 minutes, the oil pressure drops from 50 psi to 15-20 psi and temp gauge starts moving from middle to far right. Luckily I was a 100 yards from my house and I made it home. I called the shop and talked to the owner and he said may be worn bearings or oil pump problem and also suggested I change the oil since it had been a year. It just cost me significant dollars to solve the valve clearances. Anyone have any thoughts on anything I can check on my own without going back to the shop.
Steve

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 Posted: 06-28-2019 12:29 am
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redracer
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The oil pressure is directly affected by the water temperature. The CHAMPION 3 row aluminum will take care of that and is much cheaper than the 3 row staggered copper ones.
https://www.amazon.com/Champion-Cooling-Aluminum-Radiator-Jensen/dp/B00AOCV7L0/ref=sr_1_fkmr1_2?keywords=Jensen+healey+radiator&qid=1561681334&s=gateway&sr=8-2-fkmr1
Also, we shim the oil pressure relief valve 5-6mm( located on the back of the oil pump housing and held in place with a split pin; it can be done with the distributor removed and using careful tapping out of the split pin into the distributor shaft hole). Originally, the pressure relief was spring loaded for 55 psi, much too little for a 7000 rpm engine.
keep us posted, bruce, Red racer

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 Posted: 06-28-2019 03:41 pm
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Esprit2
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Steve,
From what you describe, it sounds like over-heating is the root-cause, and that leads to the drop in oil pressure as the too-hot oil thins out. The initial 50 Psi of oil pressure is about normal, and steers my thinking away from any bearing clearance issues.

Over-heating could be due to something as simple as a loose or worn V-belt not driving the water pump at full speed, but I suspect that Bruce is on the right track about the radiator being due for a good cleaning, re-core, or replacement.

IF the water pump is failing, then also consider upgrading to the later Turbo 910 impeller during the rebuild. It's longer than the stock impeller, and not a direct fit. Just take the new & old impellers to a machine shop, and have them shorten the 910 impeller's nose to match the old impeller's overall length. The rest of the rebuild is as normal.

I know, I'm splitting hairs, but tight valve clearances aren't a 'problem'. That's normal wear, it happens almost on schedule, and is routine maintenance, like the chronic 'dirty oil' problem is just maintenance.

Good luck,
Tim Engel

Attachment: Cooling - Water Pump - Impeller - 907 left & 910 right - high 94kb.jpg (Downloaded 94 times)

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 Posted: 06-28-2019 05:04 pm
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flatlanderep
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Thanks to you and Bruce for your replies. I will start with a new radiator as Bruce suggests since it is probably the original and go from there.

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 Posted: 07-09-2019 09:43 pm
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flatlanderep
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The Champion radiator arrived yesterday and I installed it. Renewed coolant and started right up. Oil pressure was 55 psi and and after 10 minutes it stayed there and temp gauge stayed in the middle. Took it out for about 10 minute drive and noticed the following. At idle, oil P drops to about 15 and then at 2000 revs it is about 20, 3000 revs 30, 4000 revs 35+ and 5000 revs 50. Is this normal? I thought that at normal driving speeds, 3000 revs, it should be about 40-45. Thoughts??
Steve

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 Posted: 07-11-2019 02:09 pm
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redracer
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You're okay for now, but usually at idle(after the engine has warmed up) the pressure would ideally be 20-25psi. Lower than this indicates slightly worn beqrings.
The pressure relief valve was set for 55psi, which for a 7000rpm engine is too low(about 10 psi for each 100rpm). We shim the relief valve up to 6mm.
Here's what I published back in December(use the "SEARCH" box for more info):

Almost forgot; while you're at it, shim the pressure relief valve.
Knock out the split pin into the distributor shaft hole, and add just under 6mm to the spring(the washers that the cam cover bolts used are a perfect size--maybe 3 washers will do it)

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 Posted: 07-13-2019 03:49 am
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CDA951
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During our epic 8,000-mile cross-country road trip in #19250 (as shown on the J-H Facebook page), we learned the nuances of our engine's oil system. I had rebuilt the engine and it had about 1,500 miles on it when we started, and bearing clearances were all within factory specs.

I come from the Porsche world, and air-cooled 911s run similar bearing clearances as the 907; the rule of thumb there is about 1 bar (14.7 PSI) of oil pressure per 1000 RPM when hot, up to 5 bar. I noticed that our 907 engine (running Total Classic 20W-50 oil) generally follows this trend, though when hot the max pressure does not go above 4 bar/60 PSI, which I would consider low for such a high-RPM engine as RedRacer states. I didn't replace any oil pump parts during the rebuild (pump rotor clearances and endplay were within spec, though I later learned from JAE that I should have replaced the rotor/annulus!).

We have the Champion radiator, JAE water pump with later impeller and an oil cooler installed. We drove the car in 100+ degree desert temps in Las Vegas on the way out and across the Mojave desert on the way back, and it was over 90 degrees and humid much of the trip, so more extreme than our customary mild weather here in Santa Barbara, CA!

I think I will try to shim the relief valve a bit to see if that helps. The downside of this "mod" is that it can cause cold pressures to be too high, which can blow out oil seals in extreme cases . . . .

Last edited on 07-13-2019 03:51 am by CDA951

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 Posted: 07-16-2019 12:15 am
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flatlanderep
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I have been cautious driving the JH, i.e., driving for only 10 minutes. Today, I was driving and it started out great, revs great, oil P 50 PSI cruising at 60 mph. Then about 15 minutes the oil P dived to 15 and the temp gauge started rising from middle. Very quickly, as I hit the gas, I was losing power and puled over and started to smell oil burning under the hood. Shut it down and let it cool for 30 min. and then started it up and made it home.
At this point, is it the water pump or oil pump problem? Again, Champion radiator installed last week.

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 Posted: 07-16-2019 12:55 am
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redracer
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Sorry to hear; it's certainly not the new radiator.
You said you smelled oil burning; first determine where it's coming from and then one can make a remedy.
Very strange the pressure would drop as quickly as you made it sound.
Are the cam covers leaking?; is it coming from around the distributor?; you may have to use some engine cleaner to determine the location of the oil leak.
keep us posted
bruce

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 Posted: 07-18-2019 02:00 am
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flatlanderep
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There are no oil leaks any where. I think the burning smell is related to the engine over heating. Today, I changed the thermostat and the needle on the temp gauge stayed in the middle when I drove it today. Again, after about 15 minutes, oil pressure decreased and it was getting ready to stall out and I just made it home, i.e., restricting my drives to immediate neighborhood. So it is not over heating but oil pressure changes after engine warms up. Where do I go next? Oil pump?

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 Posted: 07-18-2019 03:16 am
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CDA951
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I know that things are dicey when you are suspecting an oil pressure issue, but are you sure that it isn't an engine running issue (fuel or ignition) causing the engine to begin to stall out/idle low, and hence the drop in oil pressure?

Let's say your oil pump does have an issue---if this were the case, the engine would likely continue to run happily as the oil pressure dropped, at least until the point that it seizes up! You may have an oil pressure issue, but I don't see a failing oil pump suddenly showing itself when hot and causing stalling/lack of power issues.

Get yourself a cheap infrared temp gun to mointor engine temperatures and check if the engine is actually overheating, or if you are having an electrical/ground issue that is causing false coolant temp readings (stock J-H oil pressure gauge is mechanical, though).

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 Posted: 07-18-2019 11:36 pm
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mgreaves
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Sorry to hear about this problem.
Here's how I'd attempt a diagnosis which is not based specifically on the 907 engine;
1) When the engine is warm (not hot) check the water is flowing through the radiator (open the cap look down and see if there is movement)
2) Check cooling system pressure, (High pressure may be a hairline crack in the Head or head Gasket opening-up after the engine warms up, thereby pressuring the system with combustion gasses. (there are testers that will sniff combustion gas in coolant)
3) Check actual water when hot (most newish multimeters have a temp probe which you can insert between the hose and the radiator, you would need to get inventive here with some goo, but an actual reading that you can trust is pretty important.
If you have determined it is overheating and it's not a crack in the head or gasket, it's probably the water pump like Esprit2 commented. If your water temp is ok, and there is no excess pressure or CO2 in the water; If it isn't actually overheating you may need to change your sensor and move on to the next stage.

4) Pull the plugs and inspect (check online for plug diagnosis) you can learn a lot about an engine from the plugs.
5) Check the temperature of the Ignition coil Just put your hand on it, it shouldn't be very hot. If it's hot when the engine is hot, then this may be the problem, though it would be odd for the sensor and the coil to fail simultaneously.
Good luck

Last edited on 07-18-2019 11:38 pm by mgreaves

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