300 TDI burning coolant?

I have a 300 TDI, no coolant leaks, but level drops slightly over time. Topping off about every 500-700 miles. Now, when I coast downhill, exhaust is turning whiteish especially in low gears. And there is a smell in the cab that is not diesel… soo, what gives? Any ideas? Cheers!

Firstly, have you fitted a low coolant alarm? 300tdi suffer badly if coolant level drops due to the high level of the water pump.

I think you may have a head gasket failure if its white exhaust but I have no experience with this so better to wait for the experienced folk to give you advice on how to fully diagnose it.

However, from my experience with a slow coolant loss, check the state of your radiator. They tend to look in far better condition than they are and mine had the slightest leak on the back that I couldn't see. When I touched the back the vanes turned to dust!

Look in the coolant for oil.
If none in there look in the oil for coolant.
If none in there then it's either empty from expansion or burning it in the piston chamber , probably 3 or 4 .
Leave it for a couple of days then pull the heater plug relay.
Then cold start it and see how it fires up.
If it's lumpy then probably hgf.

300 tend to leak from the P gasket, only slightly so owners just assume the little coolant used is normal, then one day it gets just that bit lower and level drops below coolant pump and voila there pops the head gasket.

Oh and welcome to LZ.

lynall said:

300 tend to leak from the P gasket, only slightly so owners just assume the little coolant used is normal, then one day it gets just that bit lower and level drops below coolant pump and voila there pops the head gasket.

Oh and welcome to LZ.

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They only leak there if badly maintained

TheManWithTheGoldenDisco said:

They only leak there if badly maintained

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Many people still don't know they leak from or even what the P gasket is, and if the leak is slow enough the heat of the block dries out the leaky coolant.
People get complacent, so do not check anything.
Not many people lift their bonnets often enough, one bloke I know only lifted his when the screenwash ran out.

lynall said:

Many people still don't know they leak from or even what the P gasket is, and if the leak is slow enough the heat of the block dries out the leaky coolant.
People get complacent, so do not check anything.
Not many people lift their bonnets often enough, one bloke I know only lifted his when the screenwash ran out.

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Yep. Badly maintained 300s leak down the back of the water pump housing.
There a pain to do but this guy says he's got white smoke so it's probably burning coolant in piston 3 or 4....

TheManWithTheGoldenDisco said:

Yep. Badly maintained 300s leak down the back of the water pump housing.
There a pain to do but this guy says he's got white smoke so it's probably burning coolant in piston 3 or 4....

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Not sure how you think they are a pain? done a few with no issues.

TheManWithTheGoldenDisco said:

Yep. Badly maintained 300s leak down the back of the water pump housing.
There a pain to do but this guy says he's got white smoke so it's probably burning coolant in piston 3 or 4....

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Water pump on a 300tdi a pain , my 11 year old nephew done mine

Durangodefender said:

I have a 300 TDI, no coolant leaks, but level drops slightly over time. Topping off about every 500-700 miles. Now, when I coast downhill, exhaust is turning whiteish especially in low gears. And there is a smell in the cab that is not diesel… soo, what gives? Any ideas? Cheers!

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They do start chuffing at the back of the head between the engine & bulkhead it may be just starting to go, perhaps
thats the smell in the cab. ???

Could do a compression test.

kevstar said:

They do start chuffing at the back of the head between the engine & bulkhead it may be just starting to go, perhaps
thats the smell in the cab. ???

Could do a compression test.

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Compression test was done, all in range, P gasket replaced by reputable shop 4 months ago.

Great feedback from all. Not sure why white smoke and smell only show up at coasting or using engine to slow down…. Accelerating and uphill no issues whatsoever…

Durangodefender said:

Compression test was done, all in range, P gasket replaced by reputable shop 4 months ago.

Great feedback from all. Not sure why white smoke and smell only show up at coasting or using engine to slow down…. Accelerating and uphill no issues whatsoever…

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Pump timing checked?
Breathing much?

lynall said:

Pump timing checked?
Breathing much?

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P gasket and timing belt were done at the same time, should be fine?

Durangodefender said:

P gasket and timing belt were done at the same time, should be fine?

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Never assume anything, especially if this is a new issue!
I would recheck timing which is non invasive, then make damned sure the crank bolt is tight.

Durangodefender said:

Compression test was done, all in range, P gasket replaced by reputable shop 4 months ago.

Great feedback from all. Not sure why white smoke and smell only show up at coasting or using engine to slow down…. Accelerating and uphill no issues whatsoever…

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Has it been doing this for months or is it a new issue. White smoke on overrun might be unburnt fuel.

lynall said:

Never assume anything, especially if this is a new issue!
I would recheck timing which is non invasive, then make damned sure the crank bolt is tight.

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Thanks. So true. I guess my defenses popped up… just spent money on that…

Durangodefender said:

Thanks. So true. I guess my defenses popped up… just spent money on that…

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Only a few minutes work to check pump timing, you are not after checking is 100 percent, so long as hole and slots line up, then you can eliminate that from your enquiries.

If it smells like coolant or not like exhaust in the cab, the coolant could be leaking around the house to the heater (on the firewall)? Its winter here in Minnesota and I checked my expansion tank and it was almost empty, can't remember last time I looked. topped it up and then checked the next morning and it was down again. I could have just moved that fluid into the system. Need to check again this morning (hang on..), yup - about where I filled it yesterday. New section of cardboard under her and not stains.