Oil use and whistling under Acceleration

[ditchfinder]

Well, the first long run of the NTM V50 didn't go so well.

The 800 mile trip down to the middle of France seemed to be going ok, fuel use was 38mpg despite averaging 75mph on the French motorways.

There was a funny whistling noise when under hard load around 3250 rpm if going up a steep hill or overtaking but no misfires or smoke from the exhaust when applying the throttle after long downhill sections.

Within an hour of our destination after coming off the motorway and going up a right handed steep uphill bend the oil light flickered. I got the car stopped at a level layby very quickly and popped the bonnet. There was a bit of spitting around the coolant expansion tank cap but there was still lots of fluid in the tank - the level was higher than it had been before we set off.

I gave it 10 mins to let the oil settle into the sump and checked the level - it wasn't even showing on the dipstick so I put in 0.5 litres and left in another 10mins. Level was now on min mark so added another 0.5 litres.

Got to our destination and carried on checking level daily after 15-20 min drives and the level didn't drop.

Before the return journey oil and coolant checked before setting off and were fine. 5 hours in after plenty of 75mph motorway - again the whistling was still there but nothing else we pulled in for a rest and driver swap so I popped the bonnet to check all ok - it wasn't - coolant tank was nearly empty and very wet on top and oil not showing on dipstick again.

Topped up the coolant and oil and set of doing 60 with the intention of carrying on N Roads rather than motorway. At the next junction we pulled off the motorway and because I hadn't got the driving position right after our driver change due to something stopping the seat sliding back I pulled over to sort it. I thought as we had stopped I might as well take another peak under the bonnet.

Coolant tank was empty again and the underside of the bonnet was wet suggesting either a crack on the top or a blown cap - it was midnight at this point so hard to see.

Luckily I had Green Flag euro cover so got recovered, thank god we had pulled off the motorway when we did. As it was a Sunday morning at it was a public holiday in France there was no way the car was going to be fixed any time soon as everywhere was closed for 48 hours so we got a taxi to the airport and flown home, the car to be sent back to us on a truck in the next few weeks.

So when I get it back where should I start with the diagnostics?

I'm thinking expansion tank and cap is easy and I can do that on the drive - is there a chance this might have been the whistling sound I was hearing?

Then there's the oil use to try and get to the bottom of - could it be a bad PCV or most likely rings? More worrying is it possible the pressurizing of the coolant and oil use are connected?

[PNM]

What engine have you got, what mileage and what is the service history like?

[ditchfinder]

Blimey what a doofus I am

It's a 1.8 petrol with 111,000 on it. Service history to 70k was good, been a bit patchy since so I suspect it's skipped a few oil changes - especially during covid looking at mileages on MOT's

[ditchfinder]

So car finally back with me now after 3 1/2 weeks. Plan of action -

1. Inspect expansion tank and coolant pipes for cracks and leaks and replace any damaged parts. New expansion tank cap.
2. Refill and run to see if whistling noise on acceleration has stopped.
2a. If still whistling inspect air intake and hoses for any leaks.
3. If no whistling run to see if any further coolant loss
4. If no further coolant loss drive and monitor oil levels.
5. If still burning oil look to take inlet manifold off and clean/replace PCV valve and hose.
6. If it carries on burning oil then work out how much and see if it will pass an emissions test.

Anything else worth looking at or what would you do differently....?

[ditchfinder]

So expansion tank is cracked on the top and some numpty had tried glueing it before. Obviously hot coolant and glue aren't compatible. New tank on the way if this cures the whistling then it's onto looking at oil usage.

[Familyman 90]

Watching with interest for the result.

[ditchfinder]

So new expansion tank and cap on and coolant refilled.

Got the air out then revved it up to see if whistling is still there.

The whistling noise sounds like it's a vibration in the exhaust.

When the engine is revved to 3500 rpm the coolant level rises from minimum right to the top of the tank.

This doesn't seem normal to me.....or is it?

Also there's a foul smell from the exhaust when revved and there's black sooty residue on the drive near the exhaust. This is definitely not normal.

What is pressurising the coolant? no other signs of head gasket failure like mayo on the oil.

Could I have more than one issue here?

Obd2 not picking up any codes

[ditchfinder]

Had a quick chat with mechanic at local garage this morning on way in and he suspects head gasket.

Anyone know what typical costs are for this and is it worth doing on a £2k car?

Bearing in mind it could be burning oil as well as losing it via HG

[ditchfinder]

So the dealer I bought it from offered a refund with 35p/mile removed.
I decided to take it.

The two mechanics I spoke to about symptoms both thought head gasket and although fixable the fact it could be burning oil made me take the money. £800 for 2000 miles isn't great but not the worst case scenario.

Sorry we didn't get a definitive answer but I think we can chalk another 1.8 petrol onto the oil burner list