V70: Engine Diesel estate is producing light coloured smoke around 40mph

[Percival12]

Very recently our diesel V70 SE has started puffing white smoke out of the exhaust (I assume) when I put the accelerator down firmly at around 40 mph. Not when it's going slowly (however quickly I put the accelerator down) and not at the bypass speed of 55-65mph. I only noticed this out of the back mirror, and at first thought it was just a chance puff of fog or something.

The engine has been starting to sound slightly "growly" for a couple of weeks. I was thinking we might have an exhaust situation building up, but I don't think that would produce smoke (or steam?) on acceleration?

I left it with the garage today, but they can't find a problem. They say they can't see anything amiss with the exhaust, and all the pipes and wires are in the right place. So I have to wait and see.

Something isn't right. I don't want to end up dumped by the roadside during the rushhour. Has anybody any suggestions where the problem might be?

[Simon Jones]

Light smoke can indicate unburnt fuel or coolant getting into the exhaust. How's the coolant level? Is it changing (up or down) and is there any sign of excess pressure building up in the expansion tank?

[Tatsfield]

Have the coolant tested for combustion product. Hydrocarbons in the coolant would confirm a blown head gasket. Let's hope not!

[Percival12]

Thank you for those suggestions. I can check the coolant level and monitor it, I think. I'm going to go back to the garage next week when the guvnor is back from holiday (they suggest).

[Tatsfield]

The hydrocarbon test is just a litmus paper test and takes 30 seconds! Dip the paper test strip, compare the colour and impart the news. There are also reusable testers that garages use which draw up the coolant and test it and give a reading.

[Percival12]

Update: First problem: get the coolant cap off. Not a chance. Call Volvo dealer in nearest city to ask if I am doing it right. Anti-clockwise and push down, he says. Tried both those, try them again, no go. Eventually someone with an engineering degree uses a jar opener (the rubber kind, not the kind with teeth) to lever it open.

Coolant does not look low, and does not resemble mayonnaise in any way. (Someone who knows a lot more than I do, told me that is what is meant by "hydrocarbons in the coolant", I hope I got that right. Presumably not so different from hydrocarbons in pancake mix.) Asked if we should pipette some out and hold it up to the light. No, he says, not unless you want to use your turkey baster. It's clear.

So I THINK neither of those is the problem. No idea why the Coolant cap is so still, I physically can't get it off, and he had to resort to kitchenware. The push-down spring clearly isn't working. The car is about 6 years old. I thought we had the cap off in the winter, but maybe I'm wrong. It doesn't look dirty or gritty. Do I need a new one?

No manual actually tells you these things!

Ah! The litmus paper post just came up while I was writing this. Can I get litmus paper from Halfords? (If it's part of the kit, I ought to have some.)

[Model flyer]

Have you had the oil changed recently ? Or could it be diluted with fuel ? Check if the level is up. This can happen during a DPF regeneration and is usually fixed with a software update by a main dealer .Diluted fuel can cause smoking exhaust or could be bypassing the turbo oil seals causing the smoke. Another possibility is a dodgy fuel injector squirting instead of spraying or misting the fuel into a cylinder. This can cause the change in sound you mention . Try a good dose of injector cleaner .

[Percival12]

Thank you, the last service was back in July and these symptoms only started recently.

Where should I best look for injector cleaner, and do I need a particular grade/brand?

PS I recognize the signature line, I tried that at the station a couple of weeks ago and failed the second part :-)

[Model flyer]

Try any well known injector cleaner additive Redex or similar. You can also check your oil level to see if it has risen due to DPF regeneration. There is a small dipstick at bottom left of the crankcase . The oil level should be half way between the high and low marks. Dip it and also smell to see if it smells of diesel fuel ,if it does then it will need changing. How many miles has your car done ? It may not be any of these problems but worth checking the simple stuff first.

[Percival12]

We went to Halfords and put a small bottle of WYNN's injector cleaner in. So far the smoke hasn't recurred, but I haven't been far, will be going further tomorrow and see what happens.

I will look at the oil. DFP regeneration, does that just mean the filter (in that case) would need cleaning? Or does it just mean ongoing deposit of residue in the oil? It had a full service back in July, and it's about 6 years old and 145,000 miles approx. I believe it was well looked after by the previous owner's garage.

Believe in the simple stuff. One or two friends (like Tatfield above) have been muttering about head gasket. That I think is the "not simple stuff" and the garage didn't come up with anything. (But they didn't make any useful suggestions either. The govner is away at present.)