carlton x Posted January 17, 2022 Share Posted January 17, 2022 I have a 1500 midget engine in my herald and it’s recently developed low oil pressure after about 15 minutes driving on start up its in 80 then it will go down to 20 and when this happens you can hear a rattle , iv changed the oil pump and also the oil pressure relief valve clean oil and filter I’m at a loss , so I’m contemplating getting rid of the engine Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted January 17, 2022 Share Posted January 17, 2022 Sounds like you’ve got some sad bearings. 1500s like to “do” bearings, especially if held at reasonably high rpm for long periods. What diff ratio in you Herald and do you have overdrive? Mains tend to drop the most pressure and big ends make the most noise. Did you look at them while you were in there? Also, new oil pump doesn’t always mean good oil pump. You must measure them before fitting. Some are worse than the one being replaced! Nick Quote Link to comment Share on other sites More sharing options...
carlton x Posted January 17, 2022 Author Share Posted January 17, 2022 It’s got all spitfire 1500 running gear diff etc and the oil pump was brand new , no overdrive , it ran perfect for about 10 months it still runs nice just that worrying rattle when pressure drops ☹️ Quote Link to comment Share on other sites More sharing options...
PeteStupps Posted January 17, 2022 Share Posted January 17, 2022 Is this 20psi at hot idle? If so what sort of rpm is tickover? 1 Quote Link to comment Share on other sites More sharing options...
Clive Posted January 18, 2022 Share Posted January 18, 2022 Well worth dropping the sump and checking the big end, and even the main bearings. A fresh set can often give an engine a new lease of life for minimal outlay (except shampoo!) but it sounds like you have already been into the engine. What oil (brand+rating) are you using? Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted January 18, 2022 Share Posted January 18, 2022 10 hours ago, carlton x said: the oil pump was brand new Yeah….. new doesn’t always mean fit for purpose though. Did it improve matters at the time? Nick Quote Link to comment Share on other sites More sharing options...
Roger Keys Posted January 18, 2022 Share Posted January 18, 2022 I assume you changed the oil pump because you had low oil pressure? Quote Link to comment Share on other sites More sharing options...
carlton x Posted January 18, 2022 Author Share Posted January 18, 2022 17 hours ago, PeteStupps said: Is this 20psi at hot idle? If so what sort of rpm is tickover? Yes tick over is about 10k and is very smooth Quote Link to comment Share on other sites More sharing options...
carlton x Posted January 18, 2022 Author Share Posted January 18, 2022 22 minutes ago, Roger Keys said: I assume you changed the oil pump because you had low oil pressure? Yes after doing some research Quote Link to comment Share on other sites More sharing options...
carlton x Posted January 18, 2022 Author Share Posted January 18, 2022 9 hours ago, Nick Jones said: Yeah….. new doesn’t always mean fit for purpose though. Did it improve matters at the time? Nick Yes the pressure went up further than previous one Quote Link to comment Share on other sites More sharing options...
carlton x Posted January 18, 2022 Author Share Posted January 18, 2022 10 hours ago, Clive said: Well worth dropping the sump and checking the big end, and even the main bearings. A fresh set can often give an engine a new lease of life for minimal outlay (except shampoo!) but it sounds like you have already been into the engine. What oil (brand+rating) are you using? I used and and always use classic car oil Quote Link to comment Share on other sites More sharing options...
Roger Keys Posted January 18, 2022 Share Posted January 18, 2022 3 hours ago, carlton x said: Yes after doing some research Assuming the oil pressure climbs with RPM, unless the relief valve is sticking open, it seems likely the bearings are worn. Depending on crank wear, you might be OK changing the shells in situ, but still major work. Quote Link to comment Share on other sites More sharing options...
carlton x Posted January 18, 2022 Author Share Posted January 18, 2022 Thank you for all the reply’s very helpful iv got a few options but I’m thinking of just getting an engine at the moment Quote Link to comment Share on other sites More sharing options...
Clive Posted January 19, 2022 Share Posted January 19, 2022 7 hours ago, carlton x said: Thank you for all the reply’s very helpful iv got a few options but I’m thinking of just getting an engine at the moment You may be better off getting yours machined or whatever. Buying a used engine can be a case of frying pan and fire..... unless you get to see the engine running, get hot and still maintain oil pressure and drive correctly. Honestly, if you changed the oil pump, the bearings are a simple job. Or even a reground crankshaft, but that requires the engine to be taken out of the car. But then you know it is correct. Quote Link to comment Share on other sites More sharing options...
PeteStupps Posted January 19, 2022 Share Posted January 19, 2022 18 hours ago, carlton x said: Yes tick over is about 10k and is very smooth Hmm ok, so what pressure do you get at 2000 rpm when hot? The manual says it should be over 40psi I think. Not doubting your diagnosis but it's worth double checking before doing major surgery! My pressure will drop to around 20psi at tickover when hot, but that's at about 700-800rpm so doesn't concern me. You've got the rattle as well, which sounds worrying but is there any chance it's something else? Exhaust downpipe knocking on chassis rail? Quote Link to comment Share on other sites More sharing options...
carlton x Posted January 20, 2022 Author Share Posted January 20, 2022 On 19/01/2022 at 11:28, PeteStupps said: Hmm ok, so what pressure do you get at 2000 rpm when hot? The manual says it should be over 40psi I think. Not doubting your diagnosis but it's worth double checking before doing major surgery! My pressure will drop to around 20psi at tickover when hot, but that's at about 700-800rpm so doesn't concern me. You've got the rattle as well, which sounds worrying but is there any chance it's something else? Exhaust downpipe knocking on chassis rail? Definitely not the exhaust ,I wish it was ! , mine drops to around 20-25 after been driven for a while and that’s when the knocking starts it gets louder on acceleration Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted January 20, 2022 Share Posted January 20, 2022 Bearings bearings bearings. You need to drop the sump and have a look. As you can hear noises when the pressure is low, there will be damage beyond plain west, but do it now and you just might get away with new shells only. Big ends are easy enough to access, as are the centre and rear mains. The front is a bit awkward as the bridge piece has to come out to give access. I have been known to leave the front ones alone and just renew the others. The front main is generally the least worn and the bottom half of the centre main the worst….. as it takes the most thump. Obviously check out the oil pump again while you are in there. Nick 1 Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted January 21, 2022 Share Posted January 21, 2022 Wot @Nick Jones said 👆 My 1500 runs relatively low oil pressure at HOT tick-over (even with an oil cooler) but no rumblings or noises... Bearings. Quote Link to comment Share on other sites More sharing options...
carlton x Posted January 21, 2022 Author Share Posted January 21, 2022 Mmmm are you saying it’s the bearings lol , thanks for the advice very much appreciated 👍🏾 Quote Link to comment Share on other sites More sharing options...
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