zero oil pressure

[excess baggage]

Happened twice on Saturday during a blat with some seriously suicidal people. No problems while they were trying to get me to kill myself on the open road as the revs were up (I mean UP) but when we stopped the pressure dropped to nil. It returned to normal after 3-4 seconds of bliping the throttle. Do I need to fit a dry sump or is there a cheaper option? I'm going on Le July as a total novice regarding track days in a 7 and I need to give myself the best chance of getting there and back without blowing it up! Ideas please.

[oilyhands]

Sounds like classic oil surge to me, when you brake hard the oil is flung to the front of the sump and rides up out of the 'well' causing the oil pickup to suck air.. not good news, if you have a normal oil level and this is happening then you need to baffle the sump or , if you are serious about it use a back up reservoir of some kind like an accusump or apollo tank, ultimately a dry sump system will cur the problem permanently.

 

You could try a little extra oil (up to the max level) and see what happens, but every time the pressure drops you risk permanent damage to your bearings *DONT BLIP THE THROTTLE* when the pressure is zero, it may bring the pressure up but it also risk multiplying the damage, either turn the engine off and wait a minute or two, or let it idle.

 

Oily

[EFA]

Gary,

 

What engine do you have??

 

Check the oil level (should be close to max), and if its a VX take off the sump and replace the foam insert.

 

Also make sure you are not using 0-40 oil (regular Mobil 1 or Comma SynerZ) as these will give very low readings at idle when very hot. (Mobil 1 Motorsport or Comma SynerG are 15/50 and 5/40 respectively and work much better)

 

Arnie Webb

The Fat Bloke blush.gif in a Fast Temporarily Indisposed Vauxhall wink.gif

 

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[StewartG]

I don't think this is oil surge from the description given because assuming the engine is healthy the pressure should return almost as soon as the cornering or braking forces are removed and the oil can get back around the pick up pipe. It could be that the pressure does come up again much more quickly than the heavily damped gauge can register. I suspect Arnie is on the right track and thicker oil will at least alleviate the problem, an oil cooler might help. I don't know what engine you have but is it a Vx or K with hydraulic tappets as these will be the first thing to sound horrible with lubrication problems.

[Swiss_Tony]

I had similar problems with my vx.

I tried replacing the sponge baffle but this did not work.

In the end I fitted a different type of wet sump without a sponge baffle. This has cured the problem.

Not wanting to tell anyone how to suck eggs but Mobil 1 should be fine. If you use a thicker oil with the sponge baffle the problem will be worse!

What happens is the oil cannot flow through the sponge quickly enough and you end up with no oil at the pick up pipe.

 

Good luck James

 

[oilyhands]

If there is no pressure and it returns shortly that means the pickup is sucking air for a short while, if the oil isn't moving away from the pick-up, where is it? on holiday? You can call it surge or you can call it a banana, the affects are the same. Damped gauge or no, *any* interruption to oil pressure is risky.

 

Synthetic oils are much more stable under the affects of temperature than normal blended stock, even with low visocisty synthetics, the fact that the pressure returns 'to normal' in 2-3 seconds shows that the viscosity / temperature is not the problem. Hot oil doesn't shed its heat that quickly.

 

I've seen far too many wrecked angines entirely due to this phenomenon, your engine has given you a warning, ignore it at your peril.

 

Oily

[StewartG]

Whilst taking your point that hot oil doesn't cool down that quickly I still think that if it's due to surge you would see the pressure dissapear whilst the G force is being applied. If the pressure only dissapears when the engine is idling then then I might be tempted to look elsewhere. It's fairly well documented on these pages that a little while ago I suspected an oil surge problem. I changed the oil, several times, the filter, the foam baffle and even bought a QED baffled race sump all to no avail. I too hatched the "oil can't get through the blocked foam" theory, I even butchered a foam insert to try and make it more free-flow all for nothing. In the end it was the pressure releif valve.

To help further I think we need more info.

What engine is it?

What oil are you using?

Is it filled to the max on the dipstick?

What's the idle oil pressure hot and cold?

What's the oil pressure when warm at say 4000 rpm when not accelerating, cornering or braking?

What happens to the oil pressure whilst accerating hard, cornering hard to the left and then to the right?

What's the water/engine temp after a good thrash?

Does the oil you can see either in the catch tank or under the filler cap look okay or is it perhaps milky or foamy?

Finally I agree with the respondent who said don't blip the throttle to get the oil pressure back up. Extremely hot bearings starved of oil don't need any extra stress on them. I would suggest you just let the engine idle to pump oil into the bearings to cool and lubricate them. I wouldn't switch the engine off as this cuts oil flow to the bearings whilst they may be very, very hot and if the oil film breaks down the bearing may be damaged either through carbonised oil comtamination or lack of oil on restart.

Hope this helps and if you can answer the questions it might narrow the problem down.

[excess baggage]

Many thanks chaps. Problem is you all assumed it is a VX but it's a Xflow. Pressure drop happened after some fairly serious motoring. We then pulled into Goodwood and I drove in a tight circle to park. That's when the pressure dissapeared. Any more ideas? Please?

Gary

PS Oil level was up to the full mark

 

Edited by - Excess baggage on 7 May 2001 20:58:23

[oilyhands]

I most certainly didn't assume it was a Vauxhall, driving around in a tight circle will cause massive oil surge, centripedal/fugal force will fling the oil up out of the sump-well all around the engine and cause the pickup to suck air..

 

Have a re-read of my first posting.

 

oily

[excess baggage]

Oily,

I have checked with Redline and Mick is almost certain that the standard Caterham sump is baffled. Apparently Xflows suffer from 'sweeping left hand bend syndrome'. This is exactly what happened. A serious blast for 30-40 minutes, pulled into the car park at Goodwood and swept around, left handed, to park in line. Although I wouldn't have a problem going the dry sump route I have been informed that this would intrude into the passenger footwell which is not an option as the car will always need to be 'comfy' for two. How do the accusump and apollo tank options work?

Gary

[oilyhands]

The accusump is a separate accumulator tank which contains a volume of oil pressuriszed by a piston backed up by air pressure, when the oil pressure to the engine falls oil delivery is backed up by the accusump device., it can provide pre-oiling before engine starting too, its primary purpose is to prevent oil pressure loss in conditions of surge during braking or cornering, it has some side effects which may be of benefit too, lowering of the oil level in the sump and therefore potentially reducing windage losses.

 

The apollo tank is an anti cavitation (or anti-aeration) device which is a secondary oil reservoir designed to rid the oil of any air before it makes ts way to the engine, it has a secondary affect of improving oil delivery characteristics during conditions of surge.

 

Oily

 

Edited by - oilyhands on 9 May 2001 16:15:03

[Peter Carmichael]

The efficacy of the Apollo tank depends on the design of the oil pump. The k-series pump pumps air quite efficiently and self primes easily after a surge event. This means that even during surge the pressure only drops to ~30psi. Without the Apollo tank, this 30psi would be pressurised air venting the oil out of your bearings (bad); with the Apollo tank you have foam-free oil being delivered at 30psi rather than normal running of ~60.

 

I don't like Accusumps. Too little capacity, too sensitive to preload (related to expected oil viscosity/hot running oil pressure) and they don't get rid of the air. Yuk.

 

When my engine returns from Roger Kings, it will be going back in with a dry sump and the Apollo tank.

[Robster]

If the oil is 0 w 40 and thin when hot, so reducing pressure at tick over...this shouldn't be a problem should it? I would assume that the oil is still between the bearings it is just a thinner but more lubricating layer, so should cause no damage??