Urgent: Burning smell

[lloydyyy]

On my way home from work earlier, as I exited the dual carriageway and slowed down to enter the roundabout, there was a really strong burning smell coming from somewhere around the car. After a few minutes it more-or-less disappeared. I had a look around the car when I got home and couldn't see anything untoward but the smell was still lingering from somewhere. I kept the engine running as I checked the car and then this unsettling rattling noise was coming from somewhere near the alternator. I managed to record a clip using my phone and the noise is at its worst between 17-19 seconds into the video. I intend to get the car checked ASAP but would be very grateful for any advice. The car is a 2008 Mk6.5 Fiesta with about 92k miles on the clock.

Video here

 

[Tdci-Peter]

19 minutes ago, lloydyyy said:

there was a really strong burning smell coming from somewhere around the car. After a few minutes it more-or-less disappeared.

Follow your nose! The biggest risk is an electrical cable or component overheated. Electrical faults tend to have an acrid smell that really lingers. Get as close as you can to various places like the fuse boxes, behind the dash, door linings, door & boot hinges, where cables are numerous, and see if the smell is still there. Pry up trim or coverings where possible.

If there is no visible damage, and no lingering smell, it may have been a bit of vegetation flicked up on to the exhaust or brakes, that smouldered a bit.

I am not at all certain there is a link between the rattle and any overheating. It could have been there for some time, but not very obvious unless you are intently looking for a problem.

[lloydyyy]

Thanks for the advice. I'll give everywhere a good sniff! I'll also check if the wheels are hot after a quick spin, and I'll jack the car up to see if the wheels spin freely.

[lloydyyy]

I've just taken the car out for another spin. I couldn't smell the burning from anywhere inside the car (including the vents). It seemed to brake fine and didn't pull to one side. I jacked the car up span each wheel; the rear ones span fine and freely. The front driver's side seemed to have a little resistance and I could smell a faint trace of burning up close at the wheel, and I could hear the pad faintly grazing on the disc. I rotated the front passenger's side wheel which seemed to have span a bit more freely and I couldn't really hear the pad grazing on the disc. Even though none of the wheels seemed hot, I suspect the cause of the burning smell is the driver's side brake binding - which is odd because both front calipers were replaced two years ago (about 20k miles ago).

Driver's side wheel

Passenger's side wheel

The car was suspiciously low on oil (at the minimum marker) but there wasn't any sign of a leak on the floor. I'll get the car booked in for a full brake check.

Edit: The rattle from the engine bay was bad when the car was idling. I think it could be the water pump (which is slightly leaking and due to be changed anyway).

[Tdci-Peter]

51 minutes ago, lloydyyy said:

Even though none of the wheels seemed hot, I suspect the cause of the burning smell is the driver's side brake binding - which is odd because both front calipers were replaced two years ago (about 20k miles ago).

There is often a light contact between pad & disk when turning by hand, especially if the brakes were applied (as usual) just before stopping. There is no return spring, it relies on a bit of vibration and wheel movement to ease the pads clear when running.

But check the caliper brackets. I doubt these were changed, and can develop small wear ridges that stop the pads sliding freely. If very small, a fine file can remove them. Just in the small areas where the pads contact the brackets. Also that the caliper guide pins were properly greased, and are still free. These can gunk up quite quickly, I clean & grease my caliper pins every year, a really easy job, usually.

I thought from the way the smell seemed to disappear quite quickly that it originated outside the cabin, and got in through the ventilation system. But electrical faults are potentially serious, so I did suggest a fairly thorough search.

[lloydyyy]

It's definitely coming from the driver's side area; I stuck my head in the wheel arch again this morning and in the engine bay. It seems to be around the alternator area. I think it could possibly be the timing belt and/or water pump - which would explain the area the smell is coming from and where the rattle seems to be.

My guesses are: timing belt, water pump, alternator or drive belt.

[alexp999]

I'd have thought its more likely to be the alternator itself burning out if it's making a smell. The belts wont smell, and nor should the water pump really.

The amount of electrical energy going through an alternator can easily make it smell if it's going though.

It's like a motor in reverse, think how they smell when they burn out.

[lloydyyy]

11 minutes ago, alexp999 said:

I'd have thought its more likely to be the alternator itself burning out if it's making a smell. The belts wont smell, and nor should the water pump really.

The amount of electrical energy going through an alternator can easily make it smell if it's going though.

It's like a motor in reverse, think how they smell when they burn out.

Saying that, I'm fairly sure my lights were dimmer when I took the car for a test drive last night. I might be wrong but the alternator wasn't on my mind (so I wasn't consciously of the lights) but they did seem dimmer.

Good thing the car is due a timing belt change - the alternator can be changed at the same time.

[alexp999]

Is the battery light going out when you start the engine?

[lloydyyy]

Yeah, no lights are left illuminated after starting the engine.

[Tdci-Peter]

11 minutes ago, lloydyyy said:

Yeah, no lights are left illuminated after starting the engine.

Light on would indicate a fault, but light off could still have a fault, like one phase gone. If that were the case, the alternator would still appear to work, but would put ripple onto the electrical system, that could upset some sensitive electronics, and may not be able to cope with full demand.

Burnt out coils or diodes really do pong, and release chemicals that smell for a long time after. Usually you can tell if something has burnt out, even days later.

DIY diagnosis of partial alternator faults is very difficult. A specialist test would be the best.

I would check the aux belt, ideally by removing it. Temporary seizure of alternator, a/c pulley, or tensioner pulley would make it get hot very quickly. I am not sure if the water pump is aux belt or timing belt driven. Probably timing belt. What engine is it?

If the noise is around the alternator, then aux belt related problems are more likely.

[TomsFocus]

1 hour ago, Tdci-Peter said:

I would check the aux belt, ideally by removing it. Temporary seizure of alternator, a/c pulley, or tensioner pulley would make it get hot very quickly. I am not sure if the water pump is aux belt or timing belt driven. Probably timing belt. What engine is it?

It's a 1.25...Lloyd is good at detailing the year, mark and spec of his car without giving us the engine size in previous threads as well.   So the water pump is aux driven, but on a stretch belt which isn't easily removed to try without unfortunately.

 

Something sounds pretty bad in that video though, easiest thing to do would be take it to a garage where they can use a stethoscope to pinpoint the area that's coming from.  

[lloydyyy]

Haha, you got me. I didn't realise that until you pointed it out 😂

The car's been booked in for next week to have the timing belt and water pump changed. I've given the indie a heads-up about what's happened and they'll have a thorough look at the same time. I'll keep the car off the road until it goes in.

[lloydyyy]

I've had a chat with the indie and they said they wouldn't want to quote for a replacement alternator unless they're sure that's the cause and which amperage mine is. But the car is booked in for next week.

[isetta]

If it was mine I would take the alternator drive belt off and then spin things round and see if any pulleys etc are loose like bearings gone or stiff like siezing.  A few years ago on my 2001 focus petrol 1.6 the bearing on the alternator drive belt tensioner (a spring loaded tensioner wheel)siezed and the plastic tensioner wheel melted and the belt came off (on the M1). I believe it melted because when it seized, the belt was being dragged around the stationery tensioner wheel building up loads of heat. I never smelt anything but if I had been driving around town instead of hacking down the m1 I may have done. 

[lloydyyy]

It's going in on Wednesday for its timing belt change, so the alternator will be checked at the same time.

Bit concerned that the oil level is at the minimum marker. It was last changed 12 months ago, so it's due a change, but a few months ago it was at the maximum marker. I really hope it has just burnt some off over the past few months, rather than there being a bigger problem.

There doesn't seem to be any oil in the coolant, and the oil filler cap and inside the engine looks completely clean of the typical mayo gunk.

[lloydyyy]

The car is back - they've done an absolutely brilliant job. They fitted a Gates water pump and timing belt kit, changed the auxiliary drive belt and replaced the coolant. I asked if they could also squeeze in a brake fluid change as that was due - and to be fair, they did, and did it for free. The water pump was leaking badly so I was lucky to have the work done when I did.

They used a stethoscope and traced the noise to the air con pump. I honestly thought it was the alternator but looks like I was wrong! They said the alternator is working perfectly and if I source a second-hand air con pump then they'll fit it for about £50.

[lloydyyy]

There's plenty of air con compressors on eBay so I've chosen one from a low mileage (45k miles) 2008 Mk6 Fiesta, as it'll probably have minimal wear and tear. The seller has asked if mine is a 3-bolt or 4-bolt fitting. I'm not sure, but looking at others on eBay for my car they all seem to be 4 bolt, but for other years (like 2005) or models (ST) they seem to be 3 bolt. Is there a way to check to be sure? My Fiesta is a 2008 (2002 - 2008) 3-door Mk6.5 Style Climate 1.25 petrol.

Edit: This one seems to fit my car but it looks like a 3-bolt. Pretty confused now 😫

[lloydyyy]

I put the front of the car up on some ramps and had a look at the compressor. The part number is 6S6H19D629AB. I ran my hand over the top and could see that it's definitely a 3-bolt fitting. I didn't think it would matter. Glad I checked now!

The part number of the 4-bolt compressor is YS4H-19D629-AF. Other than the number of bolts, I had no idea what the differences are between the two.

[Tdci-Peter]

5 hours ago, lloydyyy said:

The part number is 6S6H19D629AB.

Typing that into eBay gave 37 hits, from under £20 to £60 or more. If possible, try to find out if the compressor came from a car with a working a/c. If the system is de-pressurised for any length of time in a car, water can get in, and if it is operated, it will not be getting oil (there is oil in the refridgerant circuit.) This can damage the compressor.

There are lots of variants for the compressor, I could not make any sense of it, so the part number you have is the best way.

£50 is a very good price to fit the pump & re-fill the system.

[lloydyyy]

I was looking at this particular part (can see traces of green PAG oil in the holes where the seals are) but also looking at obtaining a compressor from a Fiesta belonging to this breakers yard as then I can find out if the car has working A/C or not.

[lloydyyy]

Part ordered. Found a compressor for £30 including delivery with a 45-day warranty, fully tested, from a breakers yard specialising in Fords and the feedback is 100%. I'll get it fitted in the week and have the system re-gassed at the same time. Hopefully that'll be the end of it.

[Tdci-Peter]

22 hours ago, lloydyyy said:

I was looking at this particular part (can see traces of green PAG oil in the holes where the seals are) but also looking at obtaining a compressor from a Fiesta belonging to this breakers yard as then I can find out if the car has working A/C or not.

It may be worth phoning up the breaker. If they are responsible, they should have de-pressurised and drained the a/c system before dismantling. There are heavy penalties on commercial operators who vent a/c systems to the atmosphere, and are caught. So they should know if it was pressurised, when it was de-pressurised, and if it was sealed up straight away. Though whether they will be honest about it is anyone's guess!

Ah, that has changed a bit with your last post, came in as I was typing! Probably as good as you can do, as I said you are reliant on them being honest and responsible. But it is vastly better than a new or re-con compressor & fill at a dealer, I suspect that would be between £500 and £1000!

 

[lloydyyy]

This is the part I've bought. Should be about £40 to fit and then £60 for a re-gas on top. There's an excellent air con specialist in Bridgend who will fit it and re-gas the system. I doubt there'll be any problems with the compressor as it comes with a 45-day warranty, but if there are any surprises during fitting and re-gassing then at least I have the warranty to fall back on.

[lloydyyy]

Phew. The air con compressor has been fitted and works fine, so the old one was definitely knackered. Happy that the horrible rattling noise has gone. The system has been pressure tested and it's holding fine so no leaks. There was a slight scare when I brought the car into the workshop from the outside and then the pressure dropped but it was just the system settling. The air con specialist has injected new oil into the compressor and then regassed the system.

I took my car to Red Dragon Air Conditioning in Bridgend. Steve (owner) seriously knows his stuff and it's put my mind at rest knowing the system has been properly checked and is working properly.