So newly built type 4 motor with about 500 miles on it now. Have been using VR1 20w50 as recommended by the gurus. At start up from cold i am pushing 80-85psi oil pressure at 2-3k rpm. This drops to around 40psi when hot and about 10psi at idle which i am happy with. However is 80psi a bit high and likely to cause oil leakage from seals? Would i be better switching to a lighter viscosity oil? Am I risking hot idle oil pressure dropping too low with a lighter viscosity ? Thoughts appreciated Oh no not another oil thread
I use 15/40 as did on all my ac vws and I get 1 bar at idle when warmed up/hot and around 4-4.5 bar at cold start so hmm interesting.. you sure your readings are correct? Maybe its worth to switch to something thinner to see if it changed anything?.. Sent from my iPhone using Tapatalk
Its a later single relief valve case which I believe just bypasses the cooler when the oil is cool & pressure high. So i believe
Have you not got a relief valve right at the end of the system as well? 80psi cold sounds scary to me. Sure your pressure gauge is right?
It’s a single relief valve next to the filter. The later type 4 cases went back to single relief system. Think i will see what i get with 10w40 oil. Might check & possibly change the spring as its the one that came with the case & could have been changed for a heavy duty one. The gauge is reasonably accurate, i was getting 50-55psi cold 40psi hot and 10psi idle with the previous engine.
On my newish type 1 I found it ran a bit cooler on 15/40 than 20/50 I think the pressure was about the same as the bypass valve worked at.
My setup with a 26mm pump and a dual relief case used to spike over 104 psi on startup at -3 C with 20W/50. Apart from popping a looseish pipe once off the oil cooler, no other issues.. Also 40-50 psi at speed warmed up around 100C I believe it was the relief valve sticking . The preservation Parts engine hits about 70 psi.. new case no wear step in the pressure relief valve drilling.. the old engine had the plunger wedged when i got it. Old engine got through so much oil it was cheapest to go with green goop Halfords tin cans of it. New engine, warranty demands 20W/50. And it runs cool.
Ok , i`ll come clean on some issues i`ve had with the engine when it was rebuilt 3-4 years ago ... First oil was 10/40 for running in so never really got hotter than it should ... all good . Changed to 20/50 GTX which i`ve always used and started using it `properly` . Temps and pressure were fine but resulted in a weird sympton of oil pressure building UP on the overun . 40-ish psi running normal temps and it spiked up to 60 psi when i shut off from full throttle - weird !! Dropped the 20/50 and tried going back to 10/40 but that ran too hot and got thin ... Sooooo ... 10/40 appeared too thin , 20/50 built up pressure on the overun - what does a guy do ?? WELL .... Currently running a 50:50 mix of 10/40 and 20/50 which seems to work apart from getting a tad hot on long runs ... Going to drop it this weekend and try GTX again , i`ll be watching this thread with interest as i`m suspecting a relief spring cock up by the builder ...
Hmm. I’d check the last bit... Remember Laurie P saying that 20/50 was a bit too thick for a “new” engine...
How can i check it’s the correct spring rate etc for a single relief case? Is it likely to be the same spring as a duel relief case?
Not the same. Somewhere in all the technical data there are spring lengths compressed and uncompressed. Using a ruler and a set of scales...
Also make sure you got og spring not the aftermarket one as I heard they might couse the high build up pressure symptoms.. Sent from my iPhone using Tapatalk
According to Bentley the loaded length is 39mm and the spring pressure is 6.8kg to 8.8kg. You have about the same pressure I’m getting on a new Type 4 and single relief case with 15w40 oil, expect mine has slightly lower hot idle pressure. Oil pressure has nothing to do with the pressure at the crank seals so don’t worry about leaks. The single relief case uses the same pressure relief valve and spring as the duel relief and the oil system works in exactly the same way as a duel relief except that excess pressure is routed back to pump suction instead of dumped to the sump. When the oil is cold and thick pressure is high and the cooler is bypassed and changing to lighter oil should reduce the oil temperature but unless you have high oil temperature I’d find something else to worry about.
Cheers Geoff thats want I wanted to here I will probably switch to a lighter oil. Duckhams Q 10W40 looks the favorite, and find something else to worry about By the way I tried a Mann w14 filter rather than the w17 and the pressure build up from startup is definitely quicker. Good call thanks
Good idea, especially in the winter, but you might find the hot idle pressure a bit low; try 15w40 if it is.
I use Valvoline VR1 20/50 in mine and my MG - the pressure holds up when hot in the MG according the gauge - no idea on the bus as no gauge but assume the same
Changed it to Mobil 1000x1 15w40. Checked the loaded spring length against the spring from the engine I removed a bit back. It was a bit longer than spec loaded so i have put the one in from the other engine that was in spec. Cold startup pressure was only about 5psi lower Haven’t had chance to take it for a run yet to see what hot pressures are.
I'm going to change my oil and filter tomorrow, I've read through this and now I'm really confused everyone seems to use a different oil, what do I buy, who do I always turn to when faced with a problem like this.... @snotty help
