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Low oil pressure and different types of relief spring?
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Author:  gmsclassics [ Sun Dec 03, 2017 4:33 am ]
Post subject:  Low oil pressure and different types of relief spring?

Noticed today that the oil pressure on the Pageant Sprint has dropped. While it has never been high (around 45 when hot at 2500+ rpm) today it was 36 hot and only 24 at tickover. Today was warm at around 25C but coolant was at 82, same as thermostat, all the time. Went up to 90 when stationary at which the fan kicked in and pulled it back down.

It is due an annual oil change (Castrol GTX 20-50) in a few weeks but has only done 1600 miles since last done. Now at 117,500 miles on the clock, of which I’ve done 34,500 over the last 19 years of ownership without anything other than routine preventative maintenance. Doesn’t burn or lose oil and no noises that would indicate concern. No rumblings from the bottom end and nothing from the cam/valves.

I don’t want to start any significant work on the car now, given in a year’s time I will have a lot more time on my hands. Hence I would rather do something short term and perhaps look at a good refresh later.

I have thought about using a different oil, Penrite HPR30 (20W-60) or even perhaps Their HPR40 (25W-70) as they talk about better oil pressure / reduced consumption. There is also possibly the question as to whether the oil pressure relief spring is functioning correctly. I say that as on another Sprint I have had one wear and eventually break. However if I take the pump apart, what do I replace the current spring with?

In my box of bits I have three different springs and two types of fittings. If I read it correctly, Rimmers don’t stock the original type, but do have an uprated one. Not sure if it is even for the Sprint though as the part number 131535UR refers back to the Dolomite 1300/1500. However, I do appear to have one that looks identical to that, as well as a bigger one that is the same diameter as the original but significantly longer. The latter was one I removed from a Sprint that was running at over 100 psi.

The only supplier of ‘original’ type springs I can find is Robsport. They have a standard and uprated version, but can’t ascertain what the difference is (although I confess I haven’t asked them!) Does anyone know or have experience of these?

Any thoughts, experience or advice welcome.

Geoff

Top is the spring that was running at over 100psi and does fit in place of the standard one (one shown at the bottom of the photo) but is much longer. Middle one appears to be the same as the 1300/1500 spring, complete with the different ends that it was with (it will have come from a pump fitted to an 1850, but who fitted it, when and why is unknown). The setup at the bottom of the photo is clearly the only one I can find in any of my three parts catalogues, covering each of the first three series cars. This is an early fourth series car though and I don't have a parts catalogue for that one!

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Author:  James467 [ Sun Dec 03, 2017 8:39 am ]
Post subject:  Re: Low oil pressure and different types of relief spring?

So your top oil pressure relief valve is a Burman type for a Burman type pump, the bottom one is a Holbourn Eaton type for one of their pumps. Robsport supply the Burman type spring. Well that's the one that they gave me!

Author:  James467 [ Sun Dec 03, 2017 8:43 am ]
Post subject:  Re: Low oil pressure and different types of relief spring?

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Author:  James467 [ Sun Dec 03, 2017 8:43 am ]
Post subject:  Re: Low oil pressure and different types of relief spring?

Hope that helps

Author:  xvivalve [ Sun Dec 03, 2017 11:46 am ]
Post subject:  Re: Low oil pressure and different types of relief spring?

When I bought the Quicksprint, it too was running off the scale in excess of 100 psi.

I removed the same spring as illustrated top and replaced with the standard graded helix type and it then ran at about 40-45 psi warm idle after rebuild.

Whether the high oil pressure contributed to the early demise of the tensioner and chain, or whether it contributed to the slight play in the jackshaft front end can now only be conjecture...

Author:  soe8m [ Sun Dec 03, 2017 11:46 am ]
Post subject:  Re: Low oil pressure and different types of relief spring?

Using thicker oil for more pressure reading is fooling yourself. In a woman's shoe store women can walk in easily to buy shoes. No pushing on the door posts when walking in. At black Friday the shop has a discount on heavy duty shoes for plus size women. A large crowd is waiting for the store on Friday to open. When the door opens the first three women are stuck while going through the door and the crowd is pushing from behind to get in. The door posts are bending by the big pressure but no one is actually getting in the store.

Jeroen

Author:  xvivalve [ Sun Dec 03, 2017 1:11 pm ]
Post subject:  Re: Low oil pressure and different types of relief spring?

The Dutch have vivid imagination...do these women have red hair?

Author:  soe8m [ Sun Dec 03, 2017 2:51 pm ]
Post subject:  Re: Low oil pressure and different types of relief spring?

Stay on topic please Alun. :wink:

Jeroen.

Author:  Carledo [ Sun Dec 03, 2017 3:04 pm ]
Post subject:  Re: Low oil pressure and different types of relief spring?

It's not even remotely the same engine, but the Carledo's Vauxhall unit is very sensitive to both time and oil grade. I run it on the recommended 10/40 semi synthetic but once put 5/30 in by mistake, within a week, I was experiencing considerable pressure loss, especially when hot. Changing back to the proper stuff fixed that, but the car also does circa 2000 miles per year, yet at close to it's annual oil change time, there is a warning drop of about 0.5bar from it's normal max of 4.5bar and idle drops from 3bar to 1bar. When I drop the oil out, it's almost as clean as the new oil going in and looks and feels fine, but it's obviously "lost it's edge" cos when I put the new oil and filter in everything returns to normal -until the next year! It's been like that for 5 years now without changing, but this year I have been using the car more and I am getting the early warning signs now rather than in March as is usual. I probably should use a better oil, that would last longer, maybe a full synthetic, but I expect I will just stay with the cheap stuff and change it a bit more frequently.

Before you start messing with what works, try an oil change first, it might just be enough to last till you have more time to deal with it!

Steve

Author:  Jon Tilson [ Sun Dec 03, 2017 3:12 pm ]
Post subject:  Re: Low oil pressure and different types of relief spring?

You only want sixty psi for the valve to open. Higher pressures cause wear in the front jackshaft bearing, which you really dont want. I cant imagine the GTX has gone out of grade after such a low mileage unless you are getting fuel in the sump somehow and its being diluted, so check carb float valves and the fuel pump diaphram

Its not hard to whip the pump off and look for anythig sinister. Wear on the lobes or the spring going weak should be easy to diagnose.

Robsport have issued warnigs about the replacement pump they sell having too stiff a Spring for TR7's and Stags that they mostly deal with and tell you to reuse your old one.

Maybe the club should think about getting some 60psi ones remade?

Not wanting to be doom monger but some of the racing boys had a similar maginitude oil prressure drop after trouble with cracks around the center main bearing cap. Hope that's not the case here.

Jonners

Author:  gmsclassics [ Mon Dec 04, 2017 7:33 am ]
Post subject:  Re: Low oil pressure and different types of relief spring?

Thanks everyone, very helpful for my thinking processes. Little did I know I would be entertained with stories of large women in a shoe shop.

So it is a Holbourn Eaton type, but given a spare spring is 12000miles and 10 days away, I haven't had a look inside yet. I have changed the oil and filter, after adding flushing 'stuff' and running with that for 20 minutes. Used the standard Castrol 20W-50 that I've used for decades. Incidentally the oil filter cartridge cost me $33 after my discount. That's around 20 quid! Talk about getting ripped off.

Once hot, idle is around 32psi (was 24) and at 60mph in overdrive 40psi (was 36), rising to 44psi at 4000rpm.

Next I am going to order the Robsport replacement spring and try that, but amidst the Christmas mail, that will not be until the end of next week. Ironically I dismantled another used pump I have lying around and guess what, a broken spring. I have two springs, both broken, so my logic tells me the chances are this car has either a broken one, or one well on its way to breaking.

Will let you know how I get on

Thanks again for the prompt and informative replies.

Geoff

Author:  gmsclassics [ Sat Dec 16, 2017 8:16 am ]
Post subject:  Update

Received the new spring from Robsport in 6 days, which surprised me given how near Christmas. So took the pump off today and found I don't need a spring, existing one is fine and none of the clearances in the pump are out of spec. Both the inner and outer end floats are at the max of 4 thou and there is quite a bit of fine scoring. However, that doesn't look any worse than a couple of other old pumps I have lying around.

So it might be indicative of wear within the engine which I can tackle in a years time, but not now. So will put everything back together and keep a watchful eye out for any further drop. I'm unlikely to do more than 1500 miles in the next year so fingers crossed.

Geoff

Author:  dursley92 [ Sat Dec 16, 2017 2:07 pm ]
Post subject:  Re: Low oil pressure and different types of relief spring?

This is one of the problems with having an oil pressure gauge, without it you would still be blissfully ignorant.
When we have one you will always have half an eye on it - "just in case".

Before you all ask, yes I do have one so I know.

Author:  gmsclassics [ Sun Dec 17, 2017 5:28 am ]
Post subject:  Re: Low oil pressure and different types of relief spring?

I had exactly the same thought, ignorance is bliss as the saying goes!!

Author:  gmsclassics [ Sat Dec 23, 2017 7:44 am ]
Post subject:  Re: Low oil pressure and different types of relief spring?

Got around to fitting the new spring and reassembling the oil pump yesterday evening, finishing it off today. Interesting that the O-ring between the two halves of the pump was much thicker than standard so replaced with the thinner version.

Further improvement so that when engine thoroughly hot, pressures are now 33 @ 650rpm tickover, 38 @ 1000 and 48 at 3000.

I'm happy enough with that for the moment, but will have to keep an eye on it. I must admit though to being surprised how much difference a change of oil and PRV spring has made, especially when there appeared nothing wrong with the oil or spring that were there before.

Have a good Christmas everyone, if it makes you jealous we've had two weeks of temperatures in the mid twenties, peaked at 27 today in Auckland! Now on two weeks holiday so more time to work on cars

Geoff

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