While travelling home from Devon, I noticed that the oil pressure was dropping and it got to a point where we only had 20 psi at 3000 RPM. Now although this sounds silly Im sure when i checked the oil before we left it was at the full mark, although its possible to (be a dipstick) and misread the dipstick.
So, Im a bit concerned as to 1) what is an acceptable pressure to revs scale, as 20psi is ok or idle but not really that good for 3000 rpm.
2) it is normal for mopars to use oil? The engine has no leaks and doesnt look like its burning oil. I used about a pint of oil on the journey to Devon
Oil pressure drop
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Anonymous
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Dave-R
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First or all your engine is most likely burning oil. If it does not leak when standing and if it is not sprayed around your engine bay after a run then it is burning and going out of the exhaust. Is there a fine haze on the rear bumper and lights? Thats your oil. It will be due to worn piston rings and or worn cylinder walls (the later needing a re-bore to fix).
Another place oil gets into the combustion chambers is down the valve stems if the valve guides are worn or if the valve stem seals are shot. Valve stem seals are easy to replace. Valve guides require machine work.
Also if you fill the engine with too much oil it will burn off. Never fill past the 'full' mark on the dipstick.
As for pressure. It does sound as if your oil pump is worn. However before replacing it consider these other factors.
First of all make sure that the gauge is reading correctly. You don't want to replace a pump just to find it was a bad connection on the sender.
Second make sure the oil you use is thick enough. These old engines were built with heavy oil in mind as as they wear they need a heavier oil to keep the pressure up. If the engine has never been rebuilt with new bearings you should be using a 20/50 multigrade. Anything thinner might give you the low pressure you are experiencing.
Another place oil gets into the combustion chambers is down the valve stems if the valve guides are worn or if the valve stem seals are shot. Valve stem seals are easy to replace. Valve guides require machine work.
Also if you fill the engine with too much oil it will burn off. Never fill past the 'full' mark on the dipstick.
As for pressure. It does sound as if your oil pump is worn. However before replacing it consider these other factors.
First of all make sure that the gauge is reading correctly. You don't want to replace a pump just to find it was a bad connection on the sender.
Second make sure the oil you use is thick enough. These old engines were built with heavy oil in mind as as they wear they need a heavier oil to keep the pressure up. If the engine has never been rebuilt with new bearings you should be using a 20/50 multigrade. Anything thinner might give you the low pressure you are experiencing.
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Anonymous
Well I do have an aftermarket gauge and it seems to be quite accurate. Normally I also get 60-70 psi at 3000RPM. The pressure drop was due to low oil, Im sorry if I gave the wrong impression before. Once I filled up I was back to normal. The engine did sound a bit more rattly when running at 20psi, i presume this was the lifters (these mopars have the hydraulic lifters right?)
I am using oil but I cant see any signs like dave mentions the spark plugs were sooty but not too bad but they weren't oily. I dont see any smoking so I guess I must be burning oil but not so much that id notice
As far as I know the engine had new piston rings and bottom end bearings. There is no smoke on startup which I get in my Ford Escort due to the worn valve stem seals so it cant be that can it?
I'll tak a look at that crankcase ventillation thread and see if that throws any light, cheers.
I am using oil but I cant see any signs like dave mentions the spark plugs were sooty but not too bad but they weren't oily. I dont see any smoking so I guess I must be burning oil but not so much that id notice
As far as I know the engine had new piston rings and bottom end bearings. There is no smoke on startup which I get in my Ford Escort due to the worn valve stem seals so it cant be that can it?
I'll tak a look at that crankcase ventillation thread and see if that throws any light, cheers.
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Dave-R
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So you lost a PINT and you think THAT caused pressure loss??????
The only way a low oil level will effect pressure is if there is not enough in the sump to cover the oil pick-up. The oil pick-up is only a quarter inch from the bottom of the sump. OK so windage can pick a lot of oil up but not at 2000-3000rpm.
My guess is your oil is borderline too thin. Pressure will hold up OK normally but if the engine gets too hot pressure will suddenly drop and you will hear the cam lifters (tappets).
It has happened to me before and it happened the other week to Linda.
When you stopped the engine and topped the oil up it will have cooled down. That is why your pressure came back up. 20-50 oil will stop it happening again.
The only way a low oil level will effect pressure is if there is not enough in the sump to cover the oil pick-up. The oil pick-up is only a quarter inch from the bottom of the sump. OK so windage can pick a lot of oil up but not at 2000-3000rpm.
My guess is your oil is borderline too thin. Pressure will hold up OK normally but if the engine gets too hot pressure will suddenly drop and you will hear the cam lifters (tappets).
It has happened to me before and it happened the other week to Linda.
When you stopped the engine and topped the oil up it will have cooled down. That is why your pressure came back up. 20-50 oil will stop it happening again.
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Anonymous
It sure is an interesting topic this....
There was a tiny bit of oil on the dipstick when I got to the services. I filled up with oil when the engine was still hot. The temp hadnt gone too high and I used Castrol GTX which is 15W/40 (me thinks). When the level is right even when I have droven through rush hour traffic in London on a very hot day (and believe me thats HOT), the pressure never dropped even with the same oil. So although what Dave says makes sense I reckon it was the oil level.
If the level is too low then surely the pump will be picking up a bit of air with the oil thereby thinning it out with air pockets (am i talking cak now?)
Anyway, my main concern is where does the oil go? Does everyones mopar use oil, that is as they say the burning question of this topic (pardon the pun).
Anyone recommend a good oil then?
There was a tiny bit of oil on the dipstick when I got to the services. I filled up with oil when the engine was still hot. The temp hadnt gone too high and I used Castrol GTX which is 15W/40 (me thinks). When the level is right even when I have droven through rush hour traffic in London on a very hot day (and believe me thats HOT), the pressure never dropped even with the same oil. So although what Dave says makes sense I reckon it was the oil level.
If the level is too low then surely the pump will be picking up a bit of air with the oil thereby thinning it out with air pockets (am i talking cak now?)
Anyway, my main concern is where does the oil go? Does everyones mopar use oil, that is as they say the burning question of this topic (pardon the pun).
Anyone recommend a good oil then?
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Dave-R
- Posts: 24752
- Joined: Sun Apr 18, 04 11:23 pm
- Location: Dave Robson lives in Geordieland
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Sainsburys garage. ?5.99 for 5 litres of 20/50.
Lets face it. If you are loosing it at that rate you may as well save yourself some money until you find the problem.
Normally 15/40 would be OK. 20/40 would be better though. Bear in mind that the thicker the oil the slower you will loose it too. When you have found the problem go back to your GTX if you want although I have used it in both my cars and found it 'went off' quite quickly. I have gone back to using the Magnatex "for older engines" as I have always found that a good all round oil. It may even have saved my engine as it ran for some time with no pressure at all at SPR.
No. It is NOT usual for Mopars to loose oil. I never have to top mine up and it gets used hard although the total anual milage is not great I admit. The only oil leak i have on the whole car is a very small drip of trans fluid from the front seal on the trans. Now that IS a common place to leak from.
If there was just a trace of oil on the very bottom of the dip stick then yes your problem was most likely low oil level. But to be fair to me you said it lost a pint. If the level was that low you are talking almost two quarts? I forget how the markings are calibrated and I can't be bothered to go downstairs to look at a dipstick.
You have to be either dripping it out or burning it off Markie. It can't go anywhere else!
Lets face it. If you are loosing it at that rate you may as well save yourself some money until you find the problem.
Normally 15/40 would be OK. 20/40 would be better though. Bear in mind that the thicker the oil the slower you will loose it too. When you have found the problem go back to your GTX if you want although I have used it in both my cars and found it 'went off' quite quickly. I have gone back to using the Magnatex "for older engines" as I have always found that a good all round oil. It may even have saved my engine as it ran for some time with no pressure at all at SPR.
No. It is NOT usual for Mopars to loose oil. I never have to top mine up and it gets used hard although the total anual milage is not great I admit. The only oil leak i have on the whole car is a very small drip of trans fluid from the front seal on the trans. Now that IS a common place to leak from.
If there was just a trace of oil on the very bottom of the dip stick then yes your problem was most likely low oil level. But to be fair to me you said it lost a pint. If the level was that low you are talking almost two quarts? I forget how the markings are calibrated and I can't be bothered to go downstairs to look at a dipstick.
You have to be either dripping it out or burning it off Markie. It can't go anywhere else!
Second that Magnatec "for older engines" previously called "conventional engines". Paul Worrow was hooning on the '127 and lost all his oil but didn't back off and ran with no oil for a 1/4 and his engine survived on the Magnetec residue...(apparently 
) My one after it's re-ring and hone uses next to nothing oil wise and what does go probably exits the breathers. I was checking one of Halfords top semisynthetics and it did not have as high ratings (can't remember the Standards) as Magnetec and it was the same price.....RIP OFF! I was on a diesel course and my lecturer said where do you think the money comes from to fund that great Magnatec ad. He advised going to small oil producers and getting the same rating oil but without the ad mark up! I ain't found nothing as good as Magnetec' rating for a similar price. I 
Magnetec!
) My one after it's re-ring and hone uses next to nothing oil wise and what does go probably exits the breathers. I was checking one of Halfords top semisynthetics and it did not have as high ratings (can't remember the Standards) as Magnetec and it was the same price.....RIP OFF! I was on a diesel course and my lecturer said where do you think the money comes from to fund that great Magnatec ad. He advised going to small oil producers and getting the same rating oil but without the ad mark up! I ain't found nothing as good as Magnetec' rating for a similar price. I Magnetec!<center>
The name is Kev, nowadays known as Kevvy or Pommie C***!</center>
The name is Kev, nowadays known as Kevvy or Pommie C***!</center>
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Dave-R
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- Joined: Sun Apr 18, 04 11:23 pm
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Damn you Mopar kev! 
OK so after looking at my own 440 dipstick (a new hobby of mine) I find it offers no clue at all as to what the volume is between "ADD" and "FULL".
However if it is indeed a quart between the marks then there is about 4.5 quarts distance to the bottom of the dipstick.
If Markie was 4 quarts down that equals 6.5 pints.
OK so after looking at my own 440 dipstick (a new hobby of mine) I find it offers no clue at all as to what the volume is between "ADD" and "FULL".
However if it is indeed a quart between the marks then there is about 4.5 quarts distance to the bottom of the dipstick.
If Markie was 4 quarts down that equals 6.5 pints.
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Anonymous
For what its worth. i ran up to Shakey in May with an(unknown) sump leak. The oil pressure dropped but, not much. 70psi to 60psi (@3,000rpm)or slightly less. 70 psi at normal level, lower at 'fill up' level. '.To drop to 20psi seems a bit worrying and in need of further investigation. I got thru 7 litres in 500 miles. Funny that , cos the crank is shot now!