[Closed] Any car mechanics?

Airlock in the coolant perhaps? What does the manual say about the coolant warning - does that mean level is low or it's too hot?

I suppose there's bound to be some oil left in the system - you could try flushing it yourself.

Absolutely not.

I suppose there's bound to be some oil left in the system

And it will float on the top...

Coolant light means low coolant or high temp. The coolant is not low, and on the drive home the temp rose to 90 (normal) and stayed there.

Gears Suck - what do you base that on?

The temp could be inaccurate if the coolant is not circulating properly. Some cars have two temp senders, one controlling the gauge and another that does the light. I think.

The fact the gauge starts cold, warms up to mid range, and stays there suggests it is working. Coolant light comes on 15 secs after engine start from cold.

If the temp gauge is working ok it is probably the level sensor that is faulty due to oil contamination.sensor should be in the coolant header.try disconnecting see if light stays on or goes off.if coolant level is ok sure it will be ok.

Thanks markyboy - thats pretty much where I'm at. I was just a bit surprised by the amount of oil still in the coolant. Maybe, as sbob says above, the oil floats to the top.

ps - if anybody is actually a pro-mechanic, could you say so!!!

Oils a shit to get out of a coolant system and will mess with float switches bear in mind even a little bit of oil looks like loads on top of water. I take it they put new oil in the engine so it should be easier to see if it old or new oil in the coolant if its alot of oil in the header tank.

Ps actually a mechanic.

Yes, fresh engine oil, and the coolant is dark - guessing thats old oil. Would you be happy driving on the recommendation of the garage?

Ive had recommendations to use a dishwasher tab in the coolant system to get out the oil - mad idea, or worth it?

Without seeing it myself hard to say but if it is old oil in the coolant should be no problem. Not heard of putting a dish washer tab in to flush a coolant system but it could work. Would have to flush that out thoroughly aswell as no idea how it would behave with the different metals and seals in the system.
Easier to flush system a few times, let oil float to the top and use a sucker refill and repeat till its all gone.

Thanks. When i checked the coolant level today, I think I was just shocked to still see so much oil in it, but from the replies on here, and a bit of googling, it doesn't seem unusual.

All you can do is keep flushing it.oil is a nightmare to get out of coolant system.radiator will also be contaminated and will take a while to clear .may need replaced.heater matrix also sounds contaminated if your getting a smell from heating...ps pro mechanic(there said so!!!)

Thanks - will be driving it tomorrow with a/c turned off. I'll report back if I survive!!

Im no expert (at all) but I wouldnt keep driving it in the meantime. Keep searching for answers and try Pistonheads as well or VAG forums?

Nice car btw 😀

I'm not sure exactly how a coolant level sensor works, but it's something to do with the different electrical conductivity of air and water, so by knowing where on the probe that conductivity changes, it knows the water level.
Having a coating of oil on the probe spoils the reading.

We've had head gasket and oil cooler failures on buses and it can take weeks of flushing with dishwasher tablets to get rid of all the oil.
But then that's with 30m+ of heater hoses. 😉

As long as you have manually checked the level, it's safe to ignore the warning light.

As for the air con smell, I don't see how that could be related.

obviously make sure the sensor is actually plugged in, as this will trigger the light, it will most probably be on the underside. and make sure they used the proper coolant, it needs to be g12/g12+/g13 coolant from vw/audi, it should be bright pink, as aid above, it measures the resistance across the coolant, the wrong stuff can trigger the light.

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not a pro mechanic, but like I build my own bikes, I build my own cars, and have my own modded s4 b5 😀

Many thanks everybody! Well, the car was fine on my hour commute this morning - levels and temp fine. I had to turn off the ac and open the windows though due to the smell. Definitely smells like a mix of oil/coolant - not sure whether it's just spillage from the job, or internal contamination of the heater matrix as above. Is Heater Matrix change a big job
?

Is Heater Matrix change a big job
?

In general the single most awkward job possible - there are obviously exceptions, MK2 Golfs? - most manufacturers start with the heater matrix and build the car around it.

As for the air con smell, I don't see how that could be related.

Maybe he has a pinhole leak in the matrix?

Try radweld..?

Well, the sensor hadn't been clipped back on properly, so the coolant light is sorted - just the oily smelling aircon now!

Dan, as an aside, not sure how much of a 'gauge' the temp gauge is? I've a suspicion it's got about three positions - cold, 90degs and warm.

Incidentally, how many miles??

60k ish.

Why do you say that? It takes about 5 min to slowly get to 90, not seen it hotter.

I don't think you will see it hotter - unless there's a fault.

I'd just keep a careful eye on oil and coolant levels: if the heater matrix is blocked internally, surely it wouldn't lead to an external smell?
My money is on smells from residual oil/coolant spills.....but I'm not a pro.

Ok - if that's how it's designed then no issue I guess?

If you google, I think there's a way of displaying various parameters, including coolant temp on air conditioning panel?? Seem to remember doing this on my A3.

I've a suspicion it's got about three positions - cold, 90degs and warm

That's cos cars have a thermostat to send cool and back into the engine when cold instead of through the radiator. So the hotter the engine gets the more coolant goes through the rad to keep it pegged at 90. The rad is designed to shift a lot of heat, so you only see the gague go up of the stat is fully open and the fans and the rad aren't enough to cool the engine. It has to be pretty damn hot for this to happen nowadays with modern cars, hotter than we get here in the uk.

Molgrips, I understand that, but I still don't think it';s a gauge in the traditional sense.

I don't see why not? What other sense of 'gague' is there?

I love a good stw tangential argument!!

As far as I'm aware, the 'gauge' will read 90 if the temp is within prescribed limits - but it's not a direct readout of water temp. But I may be wrong. As I say, you can display the actual water temp on the climate control panel.

Slight tangent. But was told the temp gauge on my td5 was not a proper reading
It will slowly rise to the mid point and the moment the temp goes any hotter it will just push the gauge straight into the red at the top of the dial,

Maybe utter tosh though

I reckon it'd be harder to implement logic like that than just stick a normal meter in there.

Well, I seem to have flushed out all the oil, but I still have an oil smell from the heating. Will this go over time, or do I need to change the heater matrix?

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No thanks required.

Most likely spiled coolant oil etc hiding around the engine bay. Have a bit of a cleanup in the engine bay and airintake for cabin also changing the interior pollen filterwouldnt hurt.

Oh yeah good point - spilled oil on the engine makes the car stink for ages.

Garage changed the pollen filter. The smell only comes with heat. On LOW A/C setting there is no smell at all. Ask for any heat, and immediately the smell returns.

Sounds like a spot of spilled oil on the heater.

Usually, changing the heater matrix involves pulling the entire dash - massively labour intensive so not a job you'll be asking the garage to undertake without very good reason.

Give it a while, oily smells take aaaaages to go.

(not a pro mechanic)

You could try finding the air intake for heating and spraying soapy water into it 🙂

Current plan is just to run it on cool for the summer and see how it goes. Would flushing the system with dishwasher powder get as deep as the heater matrix?

The inside of it, yes. But the air being blown into your cabin goes over the outside of it...

Would flushing the system with dishwasher powder get as deep as the heater matrix?

Assuming it did, what would it achieve?

Dishwasher tabs might dissolve the remaining oil in the cooling system but you need to be sure to flush out all the dishwash detergent as it's extremely caustic - hot caustic dishwash solution actually attacks and erodes alloy... guess how I know that?

And no, if oil was spilled on the outside of the heater matrix this won't clear it. The matrix is just a smaller version of the main engine radiator so there's an awful lot of surface, onto which runny hot oil can spread. Eventually the oil will get clogged up with dust and start to look like a badly maintained bicycle cassette.

Give it time, perhaps you're smelling oil evaporating off the manifold and other hot parts.

(Not a mechanic but a former Land Rover bodger)

Yes - if you spill oil in the engine bay on something hot (ie engine block, which is actually pretty easy to do) it makes the interior smell for ages because some of the air coming into the car comes via the engine on many cars. Speaking from personal experience.

Right, so the coolant flows inside the matrix, and air over the outside. So in theory, the fact I had oil in my coolant shouldn't mean an oily smell in the heating system. It's more likely a secondary contamination of the outside of the heating fins.

Have I got that right?

dantsw13 - Member

Right, so the coolant flows inside the matrix, and air over the outside. So in theory, the fact I had oil in my coolant shouldn't mean an oily smell in the heating system. It's more likely a secondary contamination of the outside of the heating fins.

Have I got that right?

Or a small leak in the matrix that's alowing the oily coolant in to the air passage. Radiators and the heater matrix(small rad) are a bugger to get all the oil out of.

If I had a leaky matrix, wouldn't I have had a coolant smell in the air before?

Yes to your first post - possibly to the second. But what does coolant smell like? Oil is pretty pungent, I'm not sure antifreeze is.

However, with only a trace of oil in the coolant, you'd have to be losing enough to notice it in order to smell it like that, I reckon.

Any oil visible in the engine bay anywhere? Black griminess? Or just open the bonnet see if it smells. When it's hot and running of course.

Posted 24 minutes ago #

dantsw13 - Member

If I had a leaky matrix, wouldn't I have had a coolant smell in the air before?

Possibly, although flushing has been known to cause previously week but not leaking area(or had leaked but sealed with the normal gunk that builds up in the cooling system) to leak.

Antifreeze smell is noticable if you know what it is, it's a kind of sweet smell

I'd say the current smell is sweet oily, exactly as you'd expect a mix of burnt oil and coolant to smell.

Dan, if you check your coolant and oil levels and they're not moving you're fine.
As you say, the coolant is inside the heater matrix ( it's just a heat exchanger), so there shouldn't be any smell even if the coolant inside is contaminated by oil.
At least this stuff hasn't got organophospahates in it.......

That is a slight worry, being in the aviation industry where the whole toxic air debate is a big issue.

If it was just contaminated air from the engine compartment, I'd expect some fumes whatever the temp setting.

If you're selecting a cool temp, then the air won't be passing through the heat exchanger.

Exactly, but someone above was suggesting it might just be contaminated air from spilt oil on the hot engine compartment. I'd ruled that out from the lack of smell on cold temps.

Worth adding a k- seal to the coolant.if there are any small leaks it will seal it.good stuff even if it doesn't fix it it won't do your coolant system any harm unlike some adatives. Pick it up in most good auto stores possibly even halfords for about a tenner.

Thanks.

molgrips - Member
I reckon it'd be harder to implement logic like that than just stick a normal meter in there.

Worked on various instrument clusters a few years ago, if they have a "gauge" now, it will be driven by a micro-controller, not a analog gauge. As such this needs SW and a transfer function to define where the pointer should be in relation to the temperature - which will most likely be received from the engine control unit via network comms on the car.

As others have mentioned the transfer functions are generally non-linear - as that gives an impression of more stable coolant temperature. What actually is implemented is a ramp up from cold followed by a large dead band around "normal" - typically from about 75degC to 110degC[1], with a further ramp when temps start to increase beyond that.

A tri-colour "lamp" could achieve the same effect - blue-warming up, green-just fine, red-getting a bit warm down the noisy end chaps. Though to be honest, I don't see why most people even need anything other than the over temp warning.

One consequence of this is that if you do have a "gauge", modern cars appear to warm up faster than older ones with a more traditional analog gauge.

[1] - Engine coolant happily runs at well over 100degC - one because it's pressurised, and two, the coolant additive increases the boiling point (as well as other benefits). Back in early/mid nineties - systems I worked on were designed to "boil" at 131degC at sea level with correct coolant mix, which equated to about 127degC at high european mountain pass altitudes.