oil blowing out of dipstick tube - help!

[hyperhale]

Forgive me if I am asking stupid questions on the forum but I really appreciate the support you guys have given me in the short time I have  been a club member having purchased a mk4 spit a month ago.

My latest issue came up yesterday following a trip out when the accelerator pedal snagged on the carpet resulting in max throttle in neutral whilst driving for a few seconds before freeing it.

Oh c**p what now - oil is blowing up past the dipstick leaving puddles of oil on the floor.

Engine ran fine on the way home and I already plan to change the head gasket due to a small oil leak to the rear of the engine but looking at possible damage options here....

Hopefully blown head gasket - could that be it ?

Or I guess a broken ring or bent valve  ?

I'll be removing the head and realise its the only way to know for sure but wanted to see if there were any further checks I should carry out before I do that.

Compression test results hot with throttle wide open are...

Cylinder       dry         wet
1                  152         155
2                  145         180
3                  130         170
4                  150         170

[thebrookster]

Possibly head gasket gone, have a look for either traces of water in the sump or oil in the cooling system, as either of these symptoms require more urgent action! If it is just blowing you may be able to run it for while yet, though fixing it would obviously be the better option!!

The other possibility is piston rings, which may well have taken a hammering with WOT! Certainly the compression results you give hint at that, your #1 result has not changed between wet and dry tests so that is a possible culprit. Your compression results may suggest a bottom end rebuild could do to be planned anyway, as you have a fair jump in the wet tests!

[thebrookster]

Argh, posting too early!!

I would think a bent valve is unlikely, however you will be able to check for that by taking the rocker cover off and spinning the engine over on the starter, chances are a bent valve will show in sluggish movement, however I would expect other symptoms as well with this one, such as spitting out the carbs or backfiring more.

Hope that this helps anyway,

Cheers,

Phil

[Nick Jones]

Check the breathers are clear first but compression test results suggest the rings are not great so there may just be too much blow-by for the breather system to handle.

No bent valves with those compression figures and excessive blowby is not caused by head gasket problems.

Nick

[Velocita Rosso]

I `ve had oil (slight) coming out of the dip tube since fitting a new short engine and new head, so all was perfect
We assembled the whole lot from scratch, new timing gear etc tuned to ..ggery and you all know how well the car goes
Pistons/bores perfect 170 lbs all round............and never had any problems
All I did was, (when TB shouted to me that I had smoke) was to fit a short spring onto the dipstick, hooked around the stick at the neck and under the sump rim
(Some oil had blown out onto the exhaust, causing the smoke TB shouted about)  

[hyperhale]

Thanks to you all, really appreciate your input.

The pcv valve is all good and the problem is definitely linked to the wot yesterday , you can see the oil literally bubbling out of the dipstick tube and puddling on the floor.

Thinking ahead now as a piston ring change is a first for me, I see rimmers sell standard and various oversized rings that I assume are for engines/ oversized pistons after a rebore?

I dont know the history of the engine so will need to check the bore size I guess with a vernier but assuming its the original bore do I just purchase standard rings?

[Clive]

You need to see the pistons once the head is off. If they are not standard the oversize will be stamped on them. However, you must hone the bores if fitting new rings. And while you have the pistons/rods out you may well want to change the big end bearings. Maybe the mains and thrusts too.....
And that is assuming the bores are OK just to hone.......

[TedTaylor]

cliftyhanger wrote:

You need to see the pistons once the head is off. If they are not standard the oversize will be stamped on them. However, you must hone the bores if fitting new rings. And while you have the pistons/rods out you may well want to change the big end bearings. Maybe the mains and thrusts too.....
And that is assuming the bores are OK just to hone.......

And that the pistons themselves are sound enough to re-ring.

MUT

[Spider]

I suspect piston ring lands may have collapsed, a classic cause; over reving with no load.  :(

I do hope I am wrong as it will not be a cheap fix, new pistons etc

[JohnD]

Agree with Ian Spitfire6.

Oil "bubbling" out of the dipstick tube, to indicates excess crankcase pressure, but "clear breathers".
May not be necessary to remove rocker cover - just the oil filler cap.     How does the dip tube behave with that removed?
And is there a Mighty Wind blowing out of the rocker, instead of the usual light breeze?

If the bubbling stops, then you have a breather problem.    Is your rocker cover one with a small box tack welded inside over the breather?  Originally full of wire wool to catch droplets of oil, it can get clogged over the years.   Either remove box or scrape the wool out.

A Mighty Wind does mean excess blow by.

And your compressions.  No increase on No.1 when 'wet';  to me, means a valve seat problem.

JOhn

[hyperhale]

JohnD wrote:

Agree with Ian Spitfire6.

Oil "bubbling" out of the dipstick tube, to indicates excess crankcase pressure, but "clear breathers".
May not be necessary to remove rocker cover - just the oil filler cap.     How does the dip tube behave with that removed?
And is there a Mighty Wind blowing out of the rocker, instead of the usual light breeze?

If the bubbling stops, then you have a breather problem.    Is your rocker cover one with a small box tack welded inside over the breather?  Originally full of wire wool to catch droplets of oil, it can get clogged over the years.   Either remove box or scrape the wool out.

A Mighty Wind does mean excess blow by.

And your compressions.  No increase on No.1 when 'wet';  to me, means a valve seat problem.

JOhn

Ok so I have run the engine , removed the oil filler cap and the problem instantly disappears,  put it back on and within 8-10 seconds oil is coming out of the  dipstick hole and running down the side of the engine block and dripping on the floor.

There seems to be fair wind blowing through the rocker filler hole, held a nitrile disposable glove there momentarily and it was full to bursting in seconds.

It has an aftermarket alloy rocker cover and I can feel the breeze from the vent  pipe when disconnected from the pcv valve and the valve is new so all good there and I had no problem prior to the unfortunate WOT event on Sunday.

I have the luxury of a large garage so hope to get out there and start dismantling in the next day or so to investigate further.

Thank you all once again.

[thescrapman]

10041 wrote:

Engine ran fine on the way home and I already plan to change the head gasket due to a small oil leak to the rear of the engine but looking at possible damage options here....

It hasn't been mentioned but the small leak at the rear of teh engine is normal, it was "factory fitted" I think as so many do it.

It can be resolved by careful cleaning and fitment of the new gasket with a few smears of sealant ought to stop it.

But you have bigger problems now.

[JohnD]

10041 wrote:

Ok so I have run the engine , removed the oil filler cap and the problem instantly disappears,  put it back on and within 8-10 seconds oil is coming out of the  dipstick hole and running down the side of the engine block and dripping on the floor.
There seems to be fair wind blowing through the rocker filler hole, held a nitrile disposable glove there momentarily and it was full to bursting in seconds.

Yup, I'm sorry, that does sound like excess blow by, and some problem with the ring(s).
I like the glove trick!  Cunning measure!
But with the head off, do inspect your No.1 valves as well.  The wet test shows that oil doesn't improve the seal, so either a gross ring problem or valve not seating.
JOhn

[hyperhale]

thescrapman wrote:

It hasn't been mentioned but the small leak at the rear of teh engine is normal, it was "factory fitted" I think as so many do it.

It can be resolved by careful cleaning and fitment of the new gasket with a few smears of sealant ought to stop it.

But you have bigger problems now.

Thanks for the info I will bear that in mind when fitting the new gasket.

[hyperhale]

JohnD wrote:

Yup, I'm sorry, that does sound like excess blow by, and some problem with the ring(s).
I like the glove trick!  Cunning measure!
But with the head off, do inspect your No.1 valves as well.  The wet test shows that oil doesn't improve the seal, so either a gross ring problem or valve not seating.
JOhn

Thanks JOhn - I will be going in well prepared now thanks to all the great advice from you guys.

[hyperhale]

Had a chance to strip the engine down and found the exhaust pushrod for cyl 3 badly bent just below the rocker to a point that i doubt if it is opening at all...

Could this cause the blowback i am experiencing?

The head gasket has signs of leakage between cyls 2 and 3

Filling the upturned cylinder head with petrol has identified some leakage over time through the valves but the seatings look pretty good so will re grind and decoke.

The bores show no sign of visible scoring, a minimal lip at the top where the piston reaches tdc.

The pistons are my worry as although no physical damage can be seen to the  lands I assume the rings are worn from my compression test detailed at the start of this post and there is a lot of up / down play  in the land against the top compression ring - ranging from 20 - 22 thou.

I really need guidance on whether i need to replace both pistons and rings as have read that the top lands can wear.

Also do I need to buy just the standard size rings/ pistons ?

[thebrookster]

May I suggest at this point that pistons notwithstanding you do a full rebuild on the bottom end, particularly in regards to the camshaft? I would be worried at this point that the cam lobes may well have taken a hammering.

Sorry!!!!

Cheers,

Phil

[hyperhale]

thebrookster wrote:

May I suggest at this point that pistons notwithstanding you do a full rebuild on the bottom end, particularly in regards to the camshaft? I would be worried at this point that the cam lobes may well have taken a hammering.

Sorry!!!!

Cheers,

Phil

I had hoped that  the pushrods or valve stems would have taken the brunt of it...

[JohnD]

A bent push rod!
And bent at that position, implies that the valve could not/would not open.
Stuck exhaust valve?  How does that look?  If it had stuck slightly open, then that would explain the poor compression, but doesNOT explain WHY?

Galled/worn valve guide?
Was the valve struck by the piston?  Witness marks on crown?   Again, why?  Big end bearing broken up?
And any damage to the cam follower or cam lobe?

And none of the above could explain the excess crankcase pressure.
Just an engine  rebuild might not be advisable, if cam and/or crank are damaged.

John (looking black, as always!)

[hyperhale]

JohnD wrote:

A bent push rod!
And bent at that position, implies that the valve could not/would not open.
Stuck exhaust valve?  How does that look?  If it had stuck slightly open, then that would explain the poor compression, but doesNOT explain WHY?

Galled/worn valve guide?
Was the valve struck by the piston?  Witness marks on crown?   Again, why?  Big end bearing broken up?
And any damage to the cam follower or cam lobe?

And none of the above could explain the excess crankcase pressure.
Just an engine  rebuild might not be advisable, if cam and/or crank are damaged.

John (looking black, as always!)

I have the pistons / conrods etc out checking for any play in the big end bearings as i went but all looking good, cam lobes also look good and are lifting at the same amount, no damage to cam followers and no sign of marks on the crown.

Crank also shows no sign of damage.

I have also removed the valves , no sign of damage or excess play in the guides and the valves are freely moving in the guides.

Could it simply be the WOT that caused the bent pushrod ?

Any advice on the worn top lands and piston replacement would be much appreciated guys,  starting to feel sick to my stomach now reading some of the feedback of possible issues you guys have suggested :-(

[thebrookster]

I can't give advice on pistons etc, as not something I have any experience off on these cars.

On the rest, I certainly hope that myself and John are scaremongering, however I think we are both reading off the same hymn sheet as too why! There is a cost involved in rebuilding the full engine, however with a bit of luck you should be able to restrict that to gaskets and rings etc, if everything else proves good.

The issue to me here is that you have a bent pushrod, after having a WOT moment, and issues with pressurising the crankcase. I personally would advise checking any other linked parts as well now, as the last thing you want to do is rebuild the head then have a cam lobe break loose and ruin all the hard work again! You have the engine halfway there, so now would seem the best time to check the rest to me.

Hopefully someone else will provide technical details for you soon anyway ;)

Phil

[hyperhale]

thebrookster wrote:

I can't give advice on pistons etc, as not something I have any experience off on these cars.

On the rest, I certainly hope that myself and John are scaremongering, however I think we are both reading off the same hymn sheet as too why! There is a cost involved in rebuilding the full engine, however with a bit of luck you should be able to restrict that to gaskets and rings etc, if everything else proves good.

The issue to me here is that you have a bent pushrod, after having a WOT moment, and issues with pressurising the crankcase. I personally would advise checking any other linked parts as well now, as the last thing you want to do is rebuild the head then have a cam lobe break loose and ruin all the hard work again! You have the engine halfway there, so now would seem the best time to check the rest to me.

Hopefully someone else will provide technical details for you soon anyway ;)

Phil

Thanks Phil

So should I be inspecting the cam more closely now looking for stress cracks etc.?

[Nick Moore]

'Sick to the stomach' - don't worry, it really shouldn't be too bad. A standard rebuild should have it right again. After all, it was still running after the Throttle Incident. These are simple, tough engines!

Have you removed the engine from the car? If not, you'll need to pull it to rebuild it properly. Get a machine shop to wash the block and measure the bores. They can check for unusual wear patterns as well, and crack test the crankshaft and camshaft if you think it's necessary - I'm not sure it will be needed, but I've never rebuilt an over-revved engine. If the bores are worn enough to require a rebore, that's not an expensive job. If they are reboring, make sure they have the new piston set to measure against before boring. Different manufacturers' piston sizes vary slightly.

If the block doesn't need a rebore, have them check your old pistons very carefully. Not just by eye, have them measure everything! Conicity, gudgeon pin movement, the ring groove heights, overall piston heights... Or even better, get a micrometer and measure them yourself. They may be distorted, and the ring lands may have been slogged out. How were the old rings, by the way? Any broken? Did any seem easier to get off the piston, indicating a lack of tension?

As for the rest, check how the valves move in their guides. It's possible that the bent rod came from a valve that seized momentarily. Check each valve for straightness by rolling it, and do the same for the pushrods. If you only need to replace the bent rod, make sure it's the same length, as Triumph used various length rods. Make sure the valve springs are all the same heights when they're removed from the heads. If some have been damaged and lost their springiness, it won't be apparent while they're still on the head. Also, check the valve seats and heads. Lastly, get the machine shop to check the head for straightness, as it could have been bashed by the pistons. Of course, if that happened, there should be some marks on the piston crown!

Do you see what I'm getting at? Check everything for damage, straightness, ease of rotation, clearance and so on. And if it all seems OK, it should be.

[Nick Jones]

It's possible that the bulk of your extra blow-by was caused by the loss of exhaust valve opening on no3.  

You reported it as "driving fine" after the over-rev incident, so it must have been opening a bit at least and allow no 3 to fire.  However, it was probably struggling to clear the exhaust after firing giving higher cylinder pressures, for longer.  

With more extreme loss of lift even non-opening exhaust valves you get weird running issues caused by exhaust (or just compressed air possibly) being ejected back out of the inlet valve due to residual pressure and it can also cause piston damage due to overheating by compression effects.

Now you've got it apart, with a bit of luck all you'll need is a quick hone of the bores, new rings and new bearing shells.  I'd have a real careful look at number 3 piston though - it could have been suffering on the drive home.

Doubt the bent push-rod was caused by valve/piston contact - these are a long way from being interference engines.  Struggling to think of a good reason for the bend when the rod was apparently still in place.  Over-revving causes valve bounce which sometimes unseats pushrods, which then get bent by other valve gear, but they don't put themselves back on afterwards!

Nick

[JohnD]

Sorry, but what's a WOT moment?
JOhn