Can oil pressure be too high?

This forum is about the Fordson Dexta, Super Dexta and Petrol Dexta.
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Nick
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Can oil pressure be too high?

Post by Nick »

Hi guys, I haven't had much time to spend on the dexta lately, but I can finally see some light at the end of the very busy tunnel! So I would like to know, why is the oil pressure on my dextas engine 80psi??

Shouldn't it be about 40?

I have re-built the whole engine, new oil pump, ground crank and new bearings, new liners, one new conrod, three pistons, rings, small ends, big ends etc etc
Oh yay, look, another seized bolt! Lets get a hammer.....and some kano.....and some cider!

Bensdexta
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Re: Can oil pressure be too high?

Post by Bensdexta »

Are you sure your gauge is accurate? 80psi does seem on the high side.

Perhaps the pressure relief valve on the output side of the oil pump is not working correctly? It should be pre-set to 60psi, see lubrication section of the workshop manual. And yes manual also says that oil presure measured at the pressure switch should be 40psi, but mine was 50-60psi when I put two different gauges on it.

One other thing to check is the oil filter isn't blocked.

Guess high pressure is better than too low.. Reading the web, I gather it's not uncommon for 3-cyl Perkins(like) engines to have oil pressures above 40psi. :wink:
Bensdexta - 1961 working for a living!

Nick
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Re: Can oil pressure be too high?

Post by Nick »

Hi ben, the oil filter is brand new, as is everything really. I haven't run the engine for long, but oil is getting up to the rockers etc so im assuming its getting to the crank etc. Where would the filter be blocked?

It is a brand new gauge, meant for a major but im going to make a bracket so i can keep an eye on the pressure.

Do you reckon its safe to run it? I was thinking of taking it for a drive to see if it dropped a bit once it warms up?
Oh yay, look, another seized bolt! Lets get a hammer.....and some kano.....and some cider!

Bensdexta
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Re: Can oil pressure be too high?

Post by Bensdexta »

You say you fitted a new oil pump? Where did you get it? I believe the relief pressure is set by the spring that is fitted. Perhaps you can enquire of your pump supplier about the origin of pump & spring?

I'm guessing that it's OK to run your engine - but I'm not an expert, hopefully one will be along shortly...! I'd try to find out about the pump first. :wink:
Bensdexta - 1961 working for a living!

Nick
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Re: Can oil pressure be too high?

Post by Nick »

I bought the pump online, agriparts i think, seemed good quality.

I will have a look at the oil filter when I get chance. I did put 15w40 oil in it, just to run it in, I suppose I could get some different oil and try that?

It didnt go any higher than 80 when I revved it, so im assuming the blow off is working even though its set a bit high, didnt think I would be worried about high oil pressure lol!

Has anyone else had this problem?
Oh yay, look, another seized bolt! Lets get a hammer.....and some kano.....and some cider!

Bensdexta
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Re: Can oil pressure be too high?

Post by Bensdexta »

I wouldn't go any thinner than 15w40. I'm running SAE30 at present.

I would ask Agriline what the relief valve should be set to - bet they don't know!
Bensdexta - 1961 working for a living!

Nick
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Re: Can oil pressure be too high?

Post by Nick »

Your right ben, they have no idea!

Is the gallery where the oil pressure switch is screwed into the block before or after the oil filter?
Oh yay, look, another seized bolt! Lets get a hammer.....and some kano.....and some cider!

Nick
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Re: Can oil pressure be too high?

Post by Nick »

Hi, I checked the oil filter (which is new) at the weekend, and saw nothing that would cause this pressure, although if it were blocked wouldn't the oil pressure be low??????

I just want to check with everyone that it cannot be anything else than the pump relief valve thats faulty before I take it apart???
Oh yay, look, another seized bolt! Lets get a hammer.....and some kano.....and some cider!

Bensdexta
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Re: Can oil pressure be too high?

Post by Bensdexta »

Are you sure that your oil pressure guage is reading correctly - might be worth confirming before you start delving into the sump... :wink:
Bensdexta - 1961 working for a living!

Nick
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Re: Can oil pressure be too high?

Post by Nick »

Well I bought a brand new pressure gauge thats meant for a fordson major, so I guess that should do the job? I wonder whether I can borrow a proper oil pressure tester from a mechanic or something just to confirm it!
Oh yay, look, another seized bolt! Lets get a hammer.....and some kano.....and some cider!

Jan 59
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Re: Can oil pressure be too high?

Post by Jan 59 »

Had a similar problem after a complete overhaul of my 59 Dexta. The new pump was an original delivery from Perkins, but required the piping modification.
After start up with SAE 20 run in oil had a leaking seal of the oil filter housing. . Checked the oil pressure with a gauge in the port for the electric switch.
The oil pressure went up very high and then fall down repeating that all the time . Opened up the engine , checked all bearing shells to see if they were fitted correct. nothing wrong. This new pump had a 3 lobe inside, did not know how the original pump was built, as I throw it away. ???????????????????
In the end made up a primitive extra relief valve connected in the port for the oil pressure switch, together with a tee piece for the gauge and a piece of hose to drain excessive oil into the oil filler on the valve cover . After setting the oil pressure to some 45 psi it was reasoanble stable but the exces oil flowing from the hose was that much that it nearly overflow the rocker cover.. Had various mails with Perkins England,but??????????????????
So bought a second hand oil pump from an old Dexta , ground the rear cover flat and fitted this with the original pipe set. This pump is 4 lobe. The oil pressure is still fluctuating with a gauge straight in the switch port , but is normal for a Dexta. Due the high pressures also my oil pressure control switch was broken.
Sorry have no clue wat is wrong, but suppose the later type pumps don't match the F3/144 engine

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