Blue smoke on startup

[dern]

When I start my car in the morning when it's been left on the drive facing nose down (the drive is on a slight incline) I get blue smoke coming out of the exhaust for a couple of seconds. If I park it nose up on the drive overnight or on the flat for the whole day I don't get any blue smoke when I start it up. If I leave it nose down from warm for a few hours I don't get any blue smoke on startup.

Given that the car is an 8v 2.5l porsche 944 and rwd and the engine sits in the car front to back, am I right in assuming that probably the valve seals at the front of the engine are worn and letting oil through when oil pools at the front of the head?

If this is the case am I doing any damage to the engine leaving it like this for the time being given that I keep the oil topped up when it goes down and I park it nose up most of the time? It doesn't seem to burn any oil normally but this is only through not seeing smoke coming out of the back even when pressing on. Unfortunately I can't measure how much is lost by how much I top it up as it also leaks out of the main drive oil seal too (yes it's going to be a busy summer).

If my assumption is correct and I do the work removing the head and putting it back on, does anyone have any idea how much a shop would charge to recondition the head for me?

Any other ideas are gratefully received.

Thanks,

Mark

>>> Edited by dern on Sunday 7th March 17:48

[dern]

Hi Justin, if it starts to worry me I may take it to Northway to have a look or I may get a compression gauge and have a play.

Numbnuts, it's not overfilled with oil. If it's just the oil seals I could change those.

Danhay, £1500? Eek, I won't be doing that then, the car only cost £3000 and I can pick up another engine for £500

I'll have a tinker with it at some point, as it isn't smoking under normal use I'm not too worried but if it needs work I'll do as much as I can myself and then get a workshop to do the rest.

Cheers,

Mark

[dern]

wedg1e said:

Valve stem oil seals are normally included in a top-end gasket set. So you could use the 'decoke' excuse to get the finance approved by 'er indoors , then whip off the head and see what's what. However: last time I did this it cost me almost a grand... and I didn't even think there was any problem with the engine! Drop the valves with a spring compressor and see if they move sideways in their guides. If they do, spend your wad (or sell it quick). If not, rebuild with new seals.

I think this is the way I'll go. The gasket set is about 60 quid so I could take the top off as you suggest and if there's no play in the guides I can just do the seals. I got a quote from a local shop who will overhaul the head for me for 280 quid incl the guides (incl vat). I'm not giong to worry about it for now though as I can live with the odd puff of smoke.

Thanks for the advice.

Regards,

Mark

[dern]

B*gger, seems to be substantially worse today

Mark

[dern]

At least the rapid transition seems to suggest the seals rather than the guides. I'll get a compression tester at the weekend and make sure it is the top end.

Cheers,

Mark

PS... actually, if it changed this quickly and it was the bottom end that would indicate a broken ring wouldn't it? If that was the case then it would blow oil out all the time and not just on start up. Does that follow or is this wishful thinking?

>> Edited by dern on Monday 8th March 18:12

[dern]

Justin S said:

If it had popped a ring,you would get uneven low speed running due to loss of one compression and on the over run from speed you would get a good waft of smokey blue from the exhaust.

Ah, ok, I'll stop worrying about that one then.

Justin S said:

If you want to try the compression tester route,I have one you can use.

Thanks for the offer but I'm going to get one as they're pretty cheap and I can use it on the other wrecks I own

Regards,

Mark

[dern]

Quick update...

Firstly a confession, check oil at work yesterday and was at maximum on the dipstick... hmmm.

Bought a compression tester anyway just to be sure. I got a Gunson screw in type which holds the pressure while you crank and then releases it when you press the valve.

I followed the procedure in the haynes manual which was disconnect coil, remove all spark plugs, hold throttle wide open and crank a few times and record maximum values.

The values I got were...

Piston Dry Wet (3 squirts of oil)
1 210 210
2 210 220
3 210 220
4 210 220

The haynes manual says that anything over 165 is ok. These seem a bit high too me but it's possible the gauge is not as accurate as it might be and maybe I added a few psi by cranking more than the prereq 4 times (however you measure that).

Anyway, to my untrained eye these figures look ok. They seem to suggest that there is no leaks and that the rings are ok too as the wet figures are pretty much the same as the dry.

Judging by the high oil reading after 3 or 4 days of topping it up I'd say that that was the problem. It has cleared up to a large degree over the last day or so.

Am I reasonably safe in coming to the conclusion that the car is fine (although the owner is a complete dumb-*rse)?

Moral of the story: don't assume the obvious isn't the problem even when you are under the mistaken assumption that you're competant

Cheers,

Mark

[dern]

Justin S said:

Better check the Westies oil,as you say that leaks too!!!Might need to get the shorter dipstick.......;-)

LOL

Maybe I should get rid of them all and buy a newer car... nah, what would I do with all that spare time?

[dern]

wedg1e said:

Aye, that would tend to rule out the rings, leaving the valve stem seals as the likely culprit. Apart from the high oil level, that is...

I'll see how we get on as the oil level falls. If it continues to blow blue smoke then I'll take the head off and look for wear in the guides. If it has any or the gasket face isn't flat I'll get the head overhauled otherwise I'll put new seals in and put it back together. At least it doesn't sound like it's about to self-destruct.

Cheers,

Mark