Capri Mk1 Crossflow. Variable oil pressure for first mile.
Discussion
Hi all,
I have the 1600cc Kent engine, 103000 miles.
Have previously had rock steady 40psi at anything over 1500rpm, with 25psi at tickover. No problems here - ref Ford manual.
Now, for no apparent reason on my last 4 days I have had a VARIABLE pressure of between 40 to 5psi for the first mile, then it settles at 40 for the rest of the journey.
The variation of pressure between 40 & 5 has a cycle of about 15 seconds - imagine a 'sine wave'
The revs have no bearing on the pressure during this first mile. Seems to be only varying with cold oil.
Today I stripped the oil pump. All good condition, rotor clearances were well within spec. The two pressure relief valves in the pump housing were flushed with petrol, their springs were sound. Put in fresh Valvoline 20w/50 and new filter and the problem still there.
I don't know what to check now, does anyone have any ideas please ??
Thought I might check the pump inlet's oil strainer in the sump. Does anyone know if the sump pan can be removed without raising the engine please?
Thanking you, Capricrazy.
I have the 1600cc Kent engine, 103000 miles.
Have previously had rock steady 40psi at anything over 1500rpm, with 25psi at tickover. No problems here - ref Ford manual.
Now, for no apparent reason on my last 4 days I have had a VARIABLE pressure of between 40 to 5psi for the first mile, then it settles at 40 for the rest of the journey.
The variation of pressure between 40 & 5 has a cycle of about 15 seconds - imagine a 'sine wave'
The revs have no bearing on the pressure during this first mile. Seems to be only varying with cold oil.
Today I stripped the oil pump. All good condition, rotor clearances were well within spec. The two pressure relief valves in the pump housing were flushed with petrol, their springs were sound. Put in fresh Valvoline 20w/50 and new filter and the problem still there.
I don't know what to check now, does anyone have any ideas please ??
Thought I might check the pump inlet's oil strainer in the sump. Does anyone know if the sump pan can be removed without raising the engine please?
Thanking you, Capricrazy.
Are you sure it's not just a sensor issue? Is the sensor electric or capillary? Oil cooler fitted? Original pump or high pressure?(sorry for the bombarding of questions)
Strange how it's only when it's cold.
If you drop the sump, it's a t
t to reseal again. Why nobody ever made a 1 piece gasket I'll never know. Also make sure the pickup is seated properly into the block. It's a possibility it's cracked or moved and pulling air in when it's cold. I ran I tiny bead of sealant around the pickup pipe into the block on mine in the hope that it won't move.
Strange how it's only when it's cold.
If you drop the sump, it's a t
t to reseal again. Why nobody ever made a 1 piece gasket I'll never know. Also make sure the pickup is seated properly into the block. It's a possibility it's cracked or moved and pulling air in when it's cold. I ran I tiny bead of sealant around the pickup pipe into the block on mine in the hope that it won't move.Hi Adam & Marshalla,
Thanks for replying.
The gauge is capilliary, direct oil feed from block. Standard Capri set up, no cooler & original (good) pump.
Like your point about air getting into the suction pipe, might have thought it would get worse as oil thinned with distance but would be well worth checking. I have heard of these working loose come to think of it.
Do you know if the engine has to be lifted to get the sump pan out please?
Capricrazy.
Thanks for replying.
The gauge is capilliary, direct oil feed from block. Standard Capri set up, no cooler & original (good) pump.
Like your point about air getting into the suction pipe, might have thought it would get worse as oil thinned with distance but would be well worth checking. I have heard of these working loose come to think of it.
Do you know if the engine has to be lifted to get the sump pan out please?
Capricrazy.
Basically air is compressible and the oil can be considered to be incompressible. Increase oil pressure may just compress the air and not send the true reading to the Bourdon gauge. The air compression speed can also set up shockwave reflections in the trapped air and give spuriously high/low readings on the gauge. It is very common to see these severe fluctuations. It may not be the OPs problem but it 'sounds' very similar and worth a 'look'.
Peter
Peter
I had the same fault many years ago on a 71 MK1 Capri 1.6 (mid 80's) I tried changing the oil and filter to no avail renewed oil pump but kept same filter problem solved, I didn't investigate just assumed there was something wrong with the PRV and the rotors were scuffed anyway never seen this problem since 
same capillary gauge mine was a GT too
same capillary gauge mine was a GT too PeterBurgess said:
Basically air is compressible and the oil can be considered to be incompressible. Increase oil pressure may just compress the air and not send the true reading to the Bourdon gauge.
Come on Peter, surely you know better than that? It makes no difference that air is compressible, it can't magically reduce the pressure in the tube. Unless there is a physical blockage, oil and air in the tube will be at the exact same pressure.
Mr2Mike said:
Come on Peter, surely you know better than that? It makes no difference that air is compressible, it can't magically reduce the pressure in the tube. Unless there is a physical blockage, oil and air in the tube will be at the exact same pressure.
And can often be seen with those transparent lines looking more like a Zebra's stripes Hi All,
SUCCESS at last!!
I connected a master gauge into the block and it showed pressure varying - so gauge in the dash was OK after all.
Anyway, I put in 400ml of Wurth Engine Flusher, idled for 30 mins and drained out the sump.
As back as yer hat!
In with fresh oil and pressure goes straight to 40 and there it stays, apart from the usual 25psi at hot tickover. What a relief.
Will do another flush in a months time to make really certain it is all clear.
So, even after me cleaning out the 2 relief valves in the pump body it seems like that still wasn't good enough. Perhaps more crud got in after my manual cleaning of them.
Anyway, thanks to all of you for your comments and suggestions.
Really appreciate that.
Capricrazy.
SUCCESS at last!!
I connected a master gauge into the block and it showed pressure varying - so gauge in the dash was OK after all.
Anyway, I put in 400ml of Wurth Engine Flusher, idled for 30 mins and drained out the sump.
As back as yer hat!
In with fresh oil and pressure goes straight to 40 and there it stays, apart from the usual 25psi at hot tickover. What a relief.
Will do another flush in a months time to make really certain it is all clear.
So, even after me cleaning out the 2 relief valves in the pump body it seems like that still wasn't good enough. Perhaps more crud got in after my manual cleaning of them.
Anyway, thanks to all of you for your comments and suggestions.
Really appreciate that.
Capricrazy.
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