Rough Running Engine - White Smoke

[roy666]

Hi All – I have a rough running engine which seems to be firing on 3 cylinders only – I think. Once moving and engine warmed up it runs normally. However, today the engine would not turn over. Sounded like the engine wanted too, but was stuck, as if a cylinder was jammed. I put it in 3rd and rocked the car back.. and then she started normally, still rough running and now quite a lot of white smoke from the exhaust. The smoke did not really smell of anything so I’m thinking steam perhaps. And if that is the case then it’s the Head Gasket. Any thoughts on how I can check this out would be very appreciated. Thanks MB

[theelanman]

open the header tank......the water should smell and will be discoloured
the other is remove the oil filler cap...and look in......
if you have mayonnaise the HG has gone

[roy666]

Hi - no sludge on the oil stick... checked it at various times and all good there. Water in the header tank seems ok - but difficult to tell, I've been topping it up so much now, there's no additive left in I guess. it does not seem over smelly though.

[rip]

I had no mayo in my oil or fumy smell in my coolant when my HG went, but I had your other symptoms, ie. rough running & lots of steam.

Look inside your engine: Take out your spark plugs, check their electrodes & shine a light into each cylinder to look at the colour of your piston crowns.
One of my plugs looked oily (actually sooty & wet).
3 of my cylinders had silvery piston crowns & the bad one had a black piston crown.

[dapinky]

If the HG has gone, it will usually be in one of 2 ways - a breach between water system and oilways, or between water and cylinder......

The first would lead to the 'mayonaise' scenario, the second to white 'smoke' (steam) from the exhaust.

Either one will get worse with wear, and may be difficult to isolate in the early stages, where the first noticable difference will be in the lowering coolant level.

Logically, a breach between water/cylinder will show as a loss of coolant (as it is drawn into the cylinder during it's downstroke with valves closed) which then turns to steam on the upstroke (compression), and the next downstroke (ignition). It is thrown out of the exhaust valve on the last stroke where it cools in the pipe and returns to water vapour (white smoke).

If the breach is small, this is all that may be seen, but as it gets worse, then upon the compression stroke, the pressure in the cylinder will force it's way through the weakness in the gasket into the water system, causing the symptoms which you are trying to find (smell of hydrocarbons in the header tank).

If the leakage (water to cylinder) is noted, then the next stage will be cylinder to water - which may be quite quick, or may be many weeks (miles) away - who knows?

The 'smell test' will only show up (unless you're a bloodhound) when it gets to the last stage, but a good garage should have a piece of kit which can test for much smaller quantities of HCs in the coolant than you can smell.

Additionally, once it gets past the first stage, but not yet at the second, you may well notice that the excess pressure into the water system will manifest itself as bubbles in the coolant - this can sometimes be observed by topping up the coolant level, then running the car without the pressure cap fitted - if the coolant starts to bubble (or froth) then it is the signs of confirmation you are looking for - the difficulty with that approach is that the coolant level will keep changing during the test (getting higher as it warms up, then lower as the thermostat opens, then higher again, but also lower as coolant is drawn into and through the exhaust before getting higher as the exhaust gasses push through into the water system, leading to smelly bubbles! - and it may only breach at certain temperature ranges (before full temp or after full temp)....

.... overall, a proper HC test at a garage is the best way to diagnose it (or just rip it apart and change the HG anyway).

[Fredjohn]

Concur with all above comments re HG, but one other cause of white smoke in exhaust is a leaky servo: the engine is drawing in brake fluid and burning it off.

Whilst this may not give all your symptoms, it may be worth checking if all the other tests draw a blank. Suggest though you do all the other tests first and assume it's the servo as a last resort.

[Enright]

I only skimmed the above but I didn't see any mention of a compression test.
One of these is a good tool to have, and may be able to help you pinpoint the fault without resorting to garage bills, and leaving you with a tool to show for your troubles that you can use again at the end of it.

[roy666]

Thanks Guys.... all good info. I did take the sparks out and the discolouration on one of the cylinders was spot on. No 1 slightly black.. and the others clear. AA'd just delivered it to Kelvedon, who since have done a couple of checks.. and, Yep, its the HG, buy only around No 1. Hopefully, just the gasket and no other damage. I had my old 93 SE for 160,000 miles and nothing major went wrong with it; this 96 S2 with 50,000 and the HG goes! But thanks for all the advice. R

[roy666]

Hi Guys - just thought I would finish this off with a pic. HG definitely breached.. in fact, corroded was the word used by Kelvedon. Fortunately, only around No1 cylinder (notice the black mark bottom of the cylinder), but the head still needs to be machine skimmed.

R