Excessive oil drain down

Hilux · Jul 2, 2006

Hi all

Just got back from the Retro Cars day at Santa Pod (superb day out, highly recommended) and wondered if my car was unusual.

If left in the garage for a week etc it rattles (tappets) on start up and the oil pressure takes a couple of secs to raise then goes straight to 5. It sits on just over 3 when hot, 4+ when hot and cruising and just under 5 when hot and on full chat. If I start it up, drive a short distance (couple of miles) and then `say` fill up with fuel or start it up to move it out of the garage and then stop the low oil light comes on when started again. When hot and after a few miles this doesnt happen.

Today I drove it (thrashed it) against my mates Ferrari 360 Spyder (paddle shift) and it was as quick once up and running over 60mph (he was mortified). Stopped and saw the show, went to start it up and it still very briefly rattled (tappets) for a 1/2 sec and then went to full pressure.

Question, is this the norm? Auto2000 used semi synthetic Audi oil 10-40 on its last service and use it in all Porsches serviced (they say) but I dont remember it being that bad on Magnatec or Mobil 1. At Weltmeister Andrew stated that it was not unusual but I feel that the drain down is somewhat excessive.

What do you think? I cant think why it drains down so quick? Any clues or past experiences?

carlmthompson · Jul 2, 2006

I sometimes leave mine unstarted for a month, and it makes no noise on start-up, and I don't see the low oil light at all (apart from the usual start up period).

I would think that the oil would be okay - is there a one way valve or anything on these cars? I would think that any period of low oil pressure, however short would be bad for the engine (of course I may be wrong!)

I know BMW used to recommend Magnatec on the E30 to stop the lifters being noisy on startup, but can't see why this would stop the low oil pressure. Is it maybe a lazy Oil Pump?

But good news on the 360!

Fen · Jul 2, 2006

Mine would only be rattly after 6 weeks or so of idleness over the winter, but then it was rattly for quite a while, sometimes 3 or 4 miles.

Hilux · Jul 2, 2006

but can't see why this would stop the low oil pressure.

Its not got low oil pressure, the light never comes on I was talking about the low oil level warning light [

]

I dont think its a lazy oil pump but I`d be interested to know if there is a one way valve anywhere. Do these cars have an engine oil cooler?

It obviously fills the head with oil when cold hence the low oil level light which then goes out and stays out when the oil has circulated and reached its temperature.

The oil obviously drains down and I assume the pressure of the valves drains some of the lifters when standing for a while.

There is no big end rattle (big ends tolerate relatively low pressure anyway as volume rather than pressure is key and regardless of pressure there is only so much oil you can squeeze through the bearings) Its when the bearings wear that the volume increases and the pressure drops so that the oil doesnt move quick enough to remove the heat.

Hilux · Jul 2, 2006

but then it was rattly for quite a while, sometimes 3 or 4 miles.

Mmmmmmmmmmmmmm...........interesting. Could have been dodgy lifters? Did it rattle if you drove it each day?

I`m sure it didnt do it that much on Magnatec and the hot and cold pressures were identical. I think I might go back to it despite all the advice to the contrary.

BTW the sump I swapped recently left me with my old one which was remarkedly completely clean ie; no brown residue so it's clearly had many and frequent changes I consider so I dont think its sludge etc anywhere affecting anything

Fen · Jul 2, 2006

No, mine would only rattle if left for a looooooong time undriven. It happened twice over the winter and after at least 6 weeks of lay-up. Up to a month or so it would be quiet from startup.

The oil level light is run by a float in the sump, it's supposed to stay on, I assume for a bulb check, then go out just like an airbag or ABS light. Excessive drain down would not make it illuminate as if anything the sump level would be high. They are prone to failure though (at least on the S2, leading me to wonder if the Turbo one is the same as I can't remember what it looked like).

There is a small oil cooler in the front, it sits under the offside fog/driving lamp unit and shares the vents there with a coiled pipe to cool the PAS fluid.

Hilux · Jul 2, 2006

Excessive drain down would not make it illuminate as if anything the sump level would be high.

It doesnt. It only lights up just after it is started, run briefly and then stopped. Clearly oil is cold, around the engine and draining back slowly. This large amount of oil circulation upon startup suggests that the drain down is too easy ie; the oil drains down completely from the tappets and head/cam too readily?? [&:][&:]

Kevin Welch · Jul 2, 2006

What do you think? I cant think why it drains down so quick? Any clues or past experiences?

Presumably you've had an oil and filter change!!!
Some filters have a non return valve in them to help with the drain down problem, mostly the less expensive filters don't have this valve (cheaper production costs).
Replacing the filter might cure your problem.

Indi9xx · Jul 3, 2006

The noisey lifters on startup is probably caused by the cylinder head non return valve... After about 1989 they redesigned the valve to stop these issuesb ,but even with the new version, the problem can still occure, which is something we have been researching recently.

In particular, we have been researching a better version of the valve, which may be available soon to overcome some of these issues.

Cheap oil filters can also make things worse... the check valve in the oil filter is designed to keep oil in the crank and block oil ways on shut down.. but because the crank naturally leaks oil on shutdown, the extra valve in the head is required to keep a head of oil within the head ready for startup.

The oil level issue is probably a sticking sender..

Hilux · Jul 3, 2006

The noisey lifters on startup is probably caused by the cylinder head non return valve... After about 1989 they redesigned the valve to stop these issuesb ,but even with the new version, the problem can still occure, which is something we have been researching recently.

In particular, we have been researching a better version of the valve, which may be available soon to overcome some of these issues.

Cheap oil filters can also make things worse... the check valve in the oil filter is designed to keep oil in the crank and block oil ways on shut down.. but because the crank naturally leaks oil on shutdown, the extra valve in the head is required to keep a head of oil within the head ready for startup.

The oil level issue is probably a sticking sender..

Ahaaaaaaaaaa

I knew it was not normal. Interesting re the oil filter as this has been changed recently. I will investigate and let you know.

Its not really an issue I feel as modern oils do well on start up (paticularly Magnatec) just annoying.

berg944 · Jul 3, 2006

My turbo lifters rattle very briefly on start up in cold weather when left standing for a week.

In the winter I let the alarm immobilise the ignition and turn the engine over until the oil pressure needle moves, no rattle.

I had similar problem on my lux. Would rattle for 10 seconds on start up but it would do it again for a couple of seconds if the engine was hot.
I soon found out the problem when I removed the cam box. I could push one hydraulic lifter in with my finger, all the rest had hydraulic lock.
I believe the lifter was completely drained when cold through lack of adequate seal and would also drain very quickly when the oil was hot.
Easy diy fix (only if your confident with the cam belt) £32 for one lifter (£55 OPC)
No more rattles on start up.

Mike[:'(]

sawood12 · Jul 3, 2006

I've noticed that this is an issue on alot of modern engines as well - particularly Audi/VW engines but i've also noticed it in other manufacturers as well. I know a few that rattle a scarry amount for the first few seconds after start up and we're talking about cars that are used every day. I must be lucky since i've not noticed my 944 rattle on startup at all and it has spent way too much time sat in the garage over the past 6 months or so - but I will listen out from now on.