ppenguin Posted July 6, 2006 Report Share Posted July 6, 2006 I currently have a strange oil pressure problem on my TR3A. On start-up and running, when cold, the gauge reads a steady 70psi at 2000 rpm as per the manual but then increases as the engine gets up to operating temperature. At around 3000 rpm the gauge indicates just over 95 psi which is worrying. I have read the earlier postings, particularly those which advocate uncrewing the oil pressure relief valve but not sure if it is as simple as that. Has anyone else experienced a similar problem with a professionally rebuilt engine? The engine is using 2.2 liners and has an unleaded head with approximateley 150 miles on the clock so far. Pete P. Quote Link to post Share on other sites
Peter Nyberg Posted July 6, 2006 Report Share Posted July 6, 2006 I currently have a strange oil pressure problem on my TR3A. On start-up and running, when cold, the gauge reads a steady 70psi at 2000 rpm as per the manual but then increases as the engine gets up to operating temperature. At around 3000 rpm the gauge indicates just over 95 psi which is worrying. I have read the earlier postings, particularly those which advocate uncrewing the oil pressure relief valve but not sure if it is as simple as that. Has anyone else experienced a similar problem with a professionally rebuilt engine? The engine is using 2.2 liners and has an unleaded head with approximateley 150 miles on the clock so far.Pete P. When just started and for a some minutes thereafter the oil pressure in my 2138 TR4 engine is about 60 psi at 2000 rpm. When the engine comes up to operating temp the pressure raises to 75. I use a cheap 20/50 mineral oil. Peter Quote Link to post Share on other sites
stephen cooper Posted July 6, 2006 Report Share Posted July 6, 2006 My Spitfire used to do this a bit, from a cold start up it would be around 60psi maybe with regardless of revs, as it warmed up it would be about 60-70 at 2000 revs and more with more revs. Oil pressure was always really good. Not sure why pressure increased with temperature though... Quote Link to post Share on other sites
Nigel Lay Posted July 6, 2006 Report Share Posted July 6, 2006 TS952 is the same as Peter N's, around 60psi cold at 2000 rpm going up to about 80psi at same revs when at operating temperature. I assumed the reason is that using a 'bog standard' 20/50 oil the viscosity is higher when hot (ie the 50 end). However of course I may well be wrong! Nigel Quote Link to post Share on other sites
Les Posted July 6, 2006 Report Share Posted July 6, 2006 (edited) My TR2 oil pressure cuts off at 70psi when cold, but climbs to 95-100 when cruising steadily at 50mph and above. The car will idle at 500rpm when the pressure drops as low as 20psi. The engine was rebuilt a few thousand miles ago ( six months ) with all new shells, including the cam bearings. I use Halfords "Classic" 20/50 oil, which seems very much like Duckhams, and Valvemaster Plus in the petrol. Edited July 6, 2006 by Les Quote Link to post Share on other sites
ppenguin Posted July 7, 2006 Author Report Share Posted July 7, 2006 Thanks to you all for your replies, it's good to know that this problem is not unique. My gauge readings are very similar to yours Les except on tickover when it still reads 50+psi. I am using Duckhams 20/50 as I did during the mid 60's with my first '3A but didn't see readings as high as this. The engine on that car had done nearly 40,000 miles when I got it so maybe our rebuilt units will go the same way in time. Quote Link to post Share on other sites
unclepete Posted July 12, 2006 Report Share Posted July 12, 2006 (edited) Strip out and clean the oil pressure pressure relief valve on the side of your oil filter assembly. The oil will drain out of this with the engine off so you don't need to drain down. Replace PRV and run up engine untill WARM. Set revs to 2000rpm and adjust screw to give you 70 psi and nip up lock nut. Unc Edited July 12, 2006 by unclepete Quote Link to post Share on other sites
Nigel Lay Posted July 13, 2006 Report Share Posted July 13, 2006 Peter, Like others I have set the PRV exactly as you say but that still does not explain the pressure increase when things are hot, I would have thought the PRV would have taken care of things but it dosn't. Like Les and Pete P I rebuild the engine on TS952 and I get about a 20psi increase with a hot engine. I took the PRV apart again in the first instance and reassembled, no difference. I am not worried at all, just curious. Nigel Quote Link to post Share on other sites
unclepete Posted July 18, 2006 Report Share Posted July 18, 2006 On start-up and running, when cold, the gauge reads a steady 70psi at 2000 rpm Like others I have set the PRV exactly as you say but that still does not explain the pressure increase when things are hot The pressure relief valve is only a spring loaded ball bearing and will react differently to different oil viscosities and temperatures. I adjusted my PRV with the engine HOT. I don't know if it makes any difference but I have a spin off filter adapter on mine but have gone from the supplied oil filters to the larger capacity zetec oil filter (Ford fitting but different sizes for different oil capacities, the one supplied with the adapter is for a 1600 engine with about 7.5 pint capacity the Zetec is around 10.5 pints and is nearer the 11 pint capacity for a sidescreen) Unc Quote Link to post Share on other sites
Rhodri Posted July 18, 2006 Report Share Posted July 18, 2006 My theory is that, when starting from cold, there is air in the pipe to the pressure guage, as the oil has drained back out of it therefore the pressure registered is lower than it actually is. Once the engine has warmed up the air has been displaced by oil and a true pressure is now read on the guage. Perhaps connecting a guage with a very short pipe, close to the outlet, or an electric guage would prove or disprove my theory ...??? Quote Link to post Share on other sites
unclepete Posted July 18, 2006 Report Share Posted July 18, 2006 Rohdri Didn't think of air in the guage pipe! It's messy, but I believe you can loosen the coupling at the back of the oil guage (with the engine running) and bleed the air out. Unc Quote Link to post Share on other sites
tr4-thomas Posted July 19, 2006 Report Share Posted July 19, 2006 Rhodri, i don't think it's possible that oil can drain back out of the pipe. pipe and guage is a closed system, so once filled with oil the oil will stay there. it's easy and not that messy to bleed the system: get yourself some old clothes, start the engine, carfully loose the coupling on the back of the guage (only one turn is enough) . when oil is seeping out get it all thight again. regards thomas from germany Quote Link to post Share on other sites
Mike Kitchener Posted July 19, 2006 Report Share Posted July 19, 2006 I believe that in a closed system the pressure will be the same throughout the system , be it oil , air , beer or a mixture of all three so I wouldn't bother bleeding it.......maybe I'm just lazy!! Can't explain why pressure rises with temperature , unless of course bearing clearances close up a bit on heating. Cheers, Mike. http://mikek.9online.fr/index.htm Quote Link to post Share on other sites
unclepete Posted July 19, 2006 Report Share Posted July 19, 2006 I believe that in a closed system the pressure will be the same throughout the system , be it oil , air , beer or a mixture of all three so I wouldn't bother bleeding it.......maybe I'm just lazy!!Can't explain why pressure rises with temperature , unless of course bearing clearances close up a bit on heating. http://mikek.9online.fr/index.htm Probably because its not a closed system! The pressurised part of the oil circuit pushes the oil up to the rockers - from there its all gravity back to the sump You are right about the pessure rise with temp that's why you set the oil pressure PRV with the engine hot! Uc Quote Link to post Share on other sites
Mike Kitchener Posted July 19, 2006 Report Share Posted July 19, 2006 Probably because its not a closed system! The pressurised part of the oil circuit pushes the oil up to the rockers - from there its all gravity back to the sump Uc I was only considering the oil gauge pipe as the closed system....the rest being open....especially to ground!!! Cheers, Mike http://mikek.9online.fr/index.htm Quote Link to post Share on other sites
unclepete Posted July 19, 2006 Report Share Posted July 19, 2006 I was only considering the oil gauge pipe as the closed system....the rest being open....especially to ground!!! Cheers, Mike http://mikek.9online.fr/index.htm You are dead right Mike Once the Oil pressure guage capillary is filled the oil will stay there unless air leaks back in at the guage end. Unc Quote Link to post Share on other sites
D Murton Posted July 19, 2006 Report Share Posted July 19, 2006 My 4A also has a higher oil pressure when hot but it is only noticeable at above 2500rpm when it rises to 80 -90 psi It has also been more noticeable since the last oil change. Penrite 20/50 I have aways assumed that the oil gets thinner as it gets hot but with modern multigrades is this correct. If the viscosity rises then this could explain an increase in pressure. The other possible explanation is that the relief valve cannot pass enough oil to relieve the pressure. DaveM Quote Link to post Share on other sites
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