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Post by indianajones on Feb 4, 2012 10:27:50 GMT
Sorry to be making all these threads lol
What oil pressure should one expect from a crab?
My owners handbook suggests that it could 75psi starting from cold. 60-75psi under normal running conditions and around 10-25psi at idle.
Cheers,
Andrew
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Post by Keef on Feb 4, 2012 13:48:34 GMT
My owners handbook suggests that it could 75psi starting from cold. 60-75psi under normal running conditions and around 10-25psi at idle. Sounds about right. Engines with a few miles on may not reach 75. Perhaps around 60psi. |
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Post by indianajones on Feb 4, 2012 20:38:24 GMT
I think mine sits on 60psi when going along and when just started. Hopefully when I rebuild the engine (this is a big ticket item for down the line, after I've taken care of the rust) it'll be better  -Andrew |
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Post by dave1800 on Feb 7, 2012 1:54:28 GMT
The official figures (BMC) were 50-70psi running hot and 15-25psi at idle, again hot. Important of course to change oil and filter regularly and something ofter overlooked, clean the oil strainer with its magnet to capture metal swarf. Lots on the web about B series oil pressure, regards David Sorry to be making all these threads lol What oil pressure should one expect from a crab? My owners handbook suggests that it could 75psi starting from cold. 60-75psi under normal running conditions and around 10-25psi at idle. Cheers, Andrew |
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Post by indianajones on Feb 7, 2012 2:01:05 GMT
Had never considered that David. I'll need to look at my workshop manuals to see where the pump and strainer actually is. Also true regarding B series information on the net, thanks to the MGB there's a wealth of info and spares out there for us to feast on Cheers, Andrew |
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Post by tommydp on Oct 21, 2012 16:36:48 GMT
Picking up this thread again, as I just installed an oil pressure gauge.. Have to do something while waiting for the dizzy:-)
It's around 60 PSI when cold. Seems the oil pressure relief valve works, as it goes up to around 75 when revving then falls. On the road it's around 65-70.
What concerns me however, is that the pressure never goes below 50 PSI at slow idle, even when warm.. Seems way too high imo, would expect 15-20 or something. OK, the engine has been rebuilt, but I suppose it should have settled by now. What on earth could cause this?
Oh yes, I've double checked with my mechanical workshop type gauge.
Tommy
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Post by dave1800 on Oct 22, 2012 1:06:33 GMT
I've seen threads where MGB owners have reported high idle pressure possibly as the result of the wrong oil filter. However as your pressure is going up and down with rpm and temperature I would not worry about it. High oil pressure can be due to a faulty oil pressure relief valve which doesn't seem to be the case here (they stick open giving low pressure don't open fully leading to v high pressure at high revs), or due to a blockage in an oil way (hopefully not you would have noticed something by now) or you are just lucky having a rebuild with fine tolerances. What oil are you using? regards David Picking up this thread again, as I just installed an oil pressure gauge.. Have to do something while waiting for the dizzy:-) It's around 60 PSI when cold. Seems the oil pressure relief valve works, as it goes up to around 75 when revving then falls. On the road it's around 65-70. What concerns me however, is that the pressure never goes below 50 PSI at slow idle, even when warm.. Seems way too high imo, would expect 15-20 or something. OK, the engine has been rebuilt, but I suppose it should have settled by now. What on earth could cause this? Oh yes, I've double checked with my mechanical workshop type gauge. Tommy |
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Post by tommydp on Oct 22, 2012 5:37:43 GMT
Thanks Dave!
I'm using 10w40 now. On 20w50 the results were not that different. At least the relief valve seems to "blow off" at 75 PSI. I doubt there is a blockage, as you said I would have noticed and there's oil at the rockers.
I've also searched the net and found others who also have high idle pressure.
I believe the filter is correct, I have a spin on filter FRAM 966B, which I've always used.
I'll upload a video of the gauge when running, later.
Tommy
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Post by dave1800 on Oct 22, 2012 13:15:38 GMT
Have you changed the oil and filter after the initial running in following the rebuild? If so was the high pressure present before the oil change? If not it would seem to point to a fault within the new filter. Regards David Thanks Dave! I'm using 10w40 now. On 20w50 the results were not that different. At least the relief valve seems to "blow off" at 75 PSI. I doubt there is a blockage, as you said I would have noticed and there's oil at the rockers. I've also searched the net and found others who also have high idle pressure. I believe the filter is correct, I have a spin on filter FRAM 966B, which I've always used. I'll upload a video of the gauge when running, later. Tommy |
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Post by tommydp on Oct 22, 2012 14:14:22 GMT
I've changed the oil and filter at least once since the rebuild. The high pressure at idle was the same earlier too. Perhaps nothing to worry about, as long as it stays below 75PSI.
According to John Twist, MGB guru, the idle pressure doesn't matter. As long as it's not too low or extremely high, I suppose. The pump is capable of making pressure up to hundreds of PSI, blowing oil filter, seals etc. So I suppose the relief valve is critical! I'll post a video later. I've got a new, white shiny Iphone so will have to figure out how it all works first:-)
It seems the pressure fluctuates sometimes, especially when opening the oil filler cap. Pressure wil also drop a bit when I open the oil filler cap.
Perhaps the fluctuating is due to the fact the engine itself, tacho etc also does this at idle now and then. Hopefully the distributor will sort this, it annoys me! Perhaps I'm just being over picky..
I had a pressure gauge on a previous 1800 though, and it was 15 at hot idle and 60 when driving. Simple as that! It would drop to zero for a second when cornering or going uphill though, but that's another story!
Regards, Tommy
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Post by Keef on Oct 22, 2012 15:15:35 GMT
I had a pressure gauge on a previous 1800 though, and it was 15 at hot idle and 60 when driving. Simple as that! It would drop to zero for a second when cornering or going uphill though, but that's another story! My VDP used to show 50psi when I switched the ignition off! Turned out to be a faulty oil pressure pipe. The 1100 uses a flexible pipe between two rigid ones. Folk may have had a similar thing with brake hoses? They tend to collapse internally acting like a one way valve.  |
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Post by Penguin45 on Oct 22, 2012 17:19:11 GMT
What sort of gauge have you installed, Tommy? If it's an electric one with the pressure switch sender, they are notoriously inaccurate. The mechanical capillary types are supposed to be more accurate.
Mine currently has an E type Jag sender, which is incorrect, giving a High reading of about 35 psi. I know that it sends 40% low, so I'm not actually worried.
Chris.
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Post by tommydp on Oct 22, 2012 19:57:36 GMT
It's an electric one yes, BUT I've checked the pressure with a quality workshop type oil pressure tool too, as well as a Smiths mechanical gauge, and they all give the same high pressure reading at idle.
They won't go below approximately 50 and fluctuate a bit when idling. When revving pressure increases steadily and "blows off" at 75 PSI, as it should.
I'll try to post a video tomorrow, and hoock up the tachometer and vacuum gauge as well as the oil pressure gauge:-)
Tommy:-)
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Post by tommydp on Oct 23, 2012 22:29:49 GMT
Here are two videos showing oil pressure, and tacho too in the last one, when idling. I feel it's not right.. Click on the pics to watch. It's running at 700is rpm, the tacho fluctuates as you can see. I don't want to mess out my new Iphone, so same old phone cam. A bit hard to see, but the pressure is 60 psi idling. In the last video, which is later with the engine still hot it's actually around 70 at idle. Notice how it fluctuates when I open the oil filler cap. At least it seems to stop at 75ish psi when revving, but at slow idle it doesn't seem right. Could the relief valve be at fault I wonder? Funny thing is, just before I started filming the first video the pressure was around 45-50, then it started pulsing and rose to 60. The idle speed then starts to fluctuate/ stall a bit too, the reason is obvious I think, if you look at the picture of the spark plugs after this idle session... They are cylinder 1, 2, 3, 4 from right to left. So, is it oil? I think so as the spark seems fine. PS, after a drive the plug recovers, and shows no sign of fouling. You gotta love this car.................. But give up? never!    Close up of the gauge..  |
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Post by dave1800 on Oct 24, 2012 4:31:07 GMT
Hi Tommy Sometimes I get the feeling that you are still trying to be a teacher on this forum and bringing to the "class" some almost impossible questions! However, it is good for exercising the grey matter! My experience has always been worrying about low oil pressure, although having seen an Australian BMC service note on a B series engine that stated you don't actually need more than about 20-25PSI running and 10 at idle (I forget the precise figures) maybe my concerns were unfounded. Looking at your plugs that could be either excess fuel or oil but as it clears after a run I would hazard a guess that it could be petrol, you should be able to tell by touching and smelling it. That could be consistent with your erratic idling but then again also the distributor - you will hopefully know this when the new one finally gets through customs. As far as the high oil pressure is concerned, I would first double check your gauges on another engine. I doubt they are both at fault but it would in my view be a sensible and quick first test. If the pressure really is so high and you are clearly getting oil to the rockers which is the end of the line for the oil flow and the engine sounds sweet on your video then I wonder if the oil is flowing through the filter or just through the by bypass valve? I know the Mk1 cars had this valve, but not sure about the later engines with the screw in filter. The Mk1 cars had a blocked filter warning light operated by this valve. Maybe you should check with the engine re-builder what oil pump they fitted. I know there are high pressure pumps available for MGBs. I'm not sure why the pressure dips and then rises when the engine is accelerated, I'm not sure if that is normal or not it seems a bit strange. Let's hope some of your other "students" here have some ideas! One last thought, have you tried swopping the oil pressure release valve with a known good one -logically it shouldn't be the problem but it's one of the few parts in the oil feed system you can get to with relative ease and who knows? Regards David |
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