low oil pressure

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Farmer
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Joined: May 30th, 2010, 7:03 pm

low oil pressure

Post by Farmer »

Evening all

Went out for a blast late this afternoon for the first time in nearly 2 months as I've been so busy working and refurbishing my sons uni. accommodation .

A couple of times the oil light came on which has happened before when getting "enthusiastic" round a roundabout but usually takes a lot of provocation and pressure quickly recovers. then to my horror I noticed the oil pressure gauge showing only 1 bar pressure , I instantly dropped the pace and cruised gently home . Pressure was fine when I first struck up and I'd checked the oil , also fine .

What's the first thing to check? oil pump?
The engine seems to be running free enough , but as background information has been running poorly at low cruising speeds, which stems from a fueling issue on number one cylinder that I've yet to get to the bottom of
WhizzMan
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Re: low oil pressure

Post by WhizzMan »

I'd be looking at my big end bearings, possibly main bearings as well. The fueling issue could be causing fuel to mix in your oil, making it too thin to lubricate those bearings effectively. This being said, if you do find traces of damage there, the rest of your engine will most likely have suffered as well. It could be something totally different of course, but often, these bearings are the first to go and that does cause a drop of oil pressure.
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Farmer
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Re: low oil pressure

Post by Farmer »

Hi

Thanks , The fueling issue seems to be a lack of fuel to number one in steady running rather than too much, but I bow to your experience and will check the big ends if I get the sump off . The engine is not rattling any more than usual .

Regards
Ian
WhizzMan
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Re: low oil pressure

Post by WhizzMan »

It could be something totally different causing low oil pressure. It was just a guess based on the information that was there. Once a carburetor bowl overflows (speck of dirt between the needle valve), oil gets thinned out really quick, so it was something that seemed plausible. Please view anything posted on forums as suggestions, opinions and advice. A lot of knowledgeable people gather here, but doing diagnosis based on a few paragraphs of text is nearly impossible to do right 100% of the time, even by demi-unacceptable like Guy, let alone mere mortals like myself.

If your oil pressure overpressure valve is sticking in an "open" position you will get very similar symptoms, to name one of many other possible causes. Have you started the car at all since you drove it back home? How is the pressure when cold? Any rattles when starting, before it gets on to pressure? Any "Latte" in the oil or in the coolant? How was the oil consumption of this engine so far, before you lost pressure? When and how many miles ago was the last oil change? What specification of oil is in the engine?
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Farmer
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Re: low oil pressure

Post by Farmer »

WhizzMan wrote:It could be something totally different causing low oil pressure. It was just a guess based on the information that was there. Once a carburetor bowl overflows (speck of dirt between the needle valve), oil gets thinned out really quick, so it was something that seemed plausible. Please view anything posted on forums as suggestions, opinions and advice. A lot of knowledgeable people gather here, but doing diagnosis based on a few paragraphs of text is nearly impossible to do right 100% of the time, even by demi-unacceptable like Guy, let alone mere mortals like myself.

If your oil pressure overpressure valve is sticking in an "open" position you will get very similar symptoms, to name one of many other possible causes. Have you started the car at all since you drove it back home? How is the pressure when cold? Any rattles when starting, before it gets on to pressure? Any "Latte" in the oil or in the coolant? How was the oil consumption of this engine so far, before you lost pressure? When and how many miles ago was the last oil change? What specification of oil is in the engine?

Hey no problem, all suggestions gratefully received . I did wonder if there is a pressure relief valve somewhere that could be stuck, is it located in the pump and if so (and turns out to be the problem) can it be released externally ? The engine was running fine in terms of normal noises and no catastrophic bang or sudden change in characteristics to suggest major failure . The engine started fine later once cool but still low pressure on the gauge . Not checked for scum under the filler cap , but will do. Last oil change was less than 4000 miles ago but over a year . The car is not used a lot but I do try to start it and give it a run as regularly as possible . The engine does weep a bit of oil from various places but consumption is negligible. I use a good quality 10/40 mineral oil that is also used in our high output turbo diesel tractors .

Thanks

ian
Guy Croft
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Re: low oil pressure

Post by Guy Croft »

I can virtually guarantee it is not a relief valve or filter problem, sorry.

It has some pressure but very low (if the gauge is right) do it will not likely be the drive to the pump although a very worn spline on the oil pump drive could do it. You should pull the pump out and check it.

My money is on a bearing or sump bashed and starving the oil pump pickup, bad news is could be a main as it's not knocking..


G
WhizzMan
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Re: low oil pressure

Post by WhizzMan »

I mentioned the pressure valve since I once got tricked by that happening and it took me a while to figure it out. The valve got stuck in one location, so oil pressure was totally dependent on temperature. Because your pressure remains low with a cold engine, I agree with Guy it probably won't be that. In fact, his analysis of a main bearing fault, sounds as the most plausible cause to me, with the facts we have now.
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Farmer
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Re: low oil pressure

Post by Farmer »

Ok

Thanks one and all , I simply have no time to even take the sump off for a poke about for now , so it will need to be a winter project especialy if I need to take the crank out for main bearing scrutiny . I will revisit and report when I get to the cause, but in the mean time if anybody has any more comments they will be greatly appreciated.

Regards for now

Ian
WhizzMan
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Re: low oil pressure

Post by WhizzMan »

If you have a damaged bearing, most likely, you will spot it without having to take the crank out. Usually the bottom part where the pressure from combustion is landing on will be the one taking the damage. Even if it's the top part, your crank journal will most likely be showing signs as well, so it won't be that hard to find once you have the sump off. It's unfortunate you won't be able to drive for the remainder of the time weather will allow. Hopefully the damage will be something you can deal with so you can take your car out next spring at least.
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Farmer
Posts: 28
Joined: May 30th, 2010, 7:03 pm

Re: low oil pressure

Post by Farmer »

WhizzMan wrote:If you have a damaged bearing, most likely, you will spot it without having to take the crank out. Usually the bottom part where the pressure from combustion is landing on will be the one taking the damage. Even if it's the top part, your crank journal will most likely be showing signs as well, so it won't be that hard to find once you have the sump off. It's unfortunate you won't be able to drive for the remainder of the time weather will allow. Hopefully the damage will be something you can deal with so you can take your car out next spring at least.
Thanks for the extra info, but even if it is the cap side of a main bearing damaged, the whole set will need replacing so the engine will need to come out and the bottom end stripped to check the journals properly. All good fun !!! I'm just thankful I discovered the problem now rather than next spring. It leaves me with options if the damage is severe to bail out completely and source a fresh lump.

thank you
Ian
WhizzMan
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Re: low oil pressure

Post by WhizzMan »

Given the symptoms, chances that the engine will have to come out for repairs/replacement are high indeed. If it was my car, I'd be impatient to get to know the cause regardless of that. When you find the time to start on it, please come back here and post photos of the carnage.
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Farmer
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Joined: May 30th, 2010, 7:03 pm

Re: low oil pressure

Post by Farmer »

WhizzMan wrote:Given the symptoms, chances that the engine will have to come out for repairs/replacement are high indeed. If it was my car, I'd be impatient to get to know the cause regardless of that. When you find the time to start on it, please come back here and post photos of the carnage.
Ok

Though I'm a little disturbed by your morbid curiosity !!! Many thanks for showing an interest :)
thank you.
Ian
Brit01
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Re: low oil pressure

Post by Brit01 »

please come back here and post photos of the carnage.
Sounds like it's turning into a thread like mine with pitted oil pump gears, flat lobes, concave tappets etc.

Hope it's not as serious.
Farmer
Posts: 28
Joined: May 30th, 2010, 7:03 pm

Re: low oil pressure

Post by Farmer »

Got a chance to check the oil pressure with a different gauge today and voilà 3 bar at idle and 5 bar at high revs when warmed up . "Hienz" manual says 2.9 to 4.9 at 6000 revs . just got to get my fueling sorted to stop the poping and banging at idle and I'm away . Took it for a ride and it's a bit disconcerting driving with the oil light glowing and 0 oil pressure but the car seems fine apart from the erratic idle and general pops and bangs

Thanks all for your input

Ian
WhizzMan
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Re: low oil pressure

Post by WhizzMan »

This sounds like a busted sensor then. Lots cheaper than rebuilding your engine. I'd get a new sensor ASAP, you don't want to run your engine into bits because you are assuming oil pressure is good, even though the dial tells you otherwise. It seems you are steering towards a happy ending.
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