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Discussion Starter · #1 ·
Hi.My Car has done 56K,.. 25 of this mine, and very carefully driven. There is a coolant leak, confirmed by a pressure test. Garage says two possible causes; cracked engine head, or the egr cooler.
Interestingly, they were to force the engine to heat up ( by running at 4500 revs) in order to do a dye test and use a scope camera. However, they stopped as the engine was 'clattering' - a sign of wear only likely to get worse.
My dilemma and question is - do i replace the egr cooler as the cheaper suspect, or go for the engine rebuild / replacement as the likely cause (.. and the elephant in the room ultimately)
I notice on other threads coolant leaks are hard to locate... Also, Has anyone replaced an Engine/ rebuilt top end before ? ( its a TDI dsg 140bhp model ) Thanks
 

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You don't say what year or engine variant? The older Tdis pre- about 2010 are relatively simple but the newer CR diesels have a lot of added emissions clutter and an EGR cooler located at the back which is an absolute pig to get to and probably involves a lot of labor? 56K is very low mileage and rattles from the engine aren't healthy. Did they check the engine oil pressure? If they put a U.V test dye in the coolant, did they find it in the engine oil?

No internet poster will tell you what exactly could be wrong with an internal engine fault such as yours. Your garage is in a better position with experience and actually looking at the engine. A V.W dealership would probably only fit a new engine at great expense. Unless you have experience rebuilding engines, getting others to do it will be expensive and you never know what you are going to find until you start paying them hourly labor which could be all in vain as they dig deeper.

There aren't enough facts and a diverse range of possibilities to give you a better answer. You could have coolant leaking into and diluting oil causing serious engine problems according to how long the fault has been there? There are several things to check when looking for a coolant leak, where coolant is going and what specific evidence can be found. When cyl. head gaskets fail, the coolant system over time usually pressurises, when coolant leaks into the combustion cylinder, you often see white smoke. When coolant leaks from other places you may find it on the engine tray or floor. Some modern engines share the same water and oil pump drive with seals between the two which can fail causing coolant to mix with engine oil or vice versa because the oil is at a higher pressure.

AFIK the EGR cooler is fed with coolant using hoses or fixed pipes and it might be possible to fit a test bypass? The ECU would after time fault on low cooler temperature, but that should't stop a pressure test being done. Having built many engines in the past and time doesn't cost me, I start tearing down on the basis I have nothing to lose if I have to fit a used engine. But on a low mileage engine like yours with ownership history I might take that chance as a used engine is always a risk. You can start from the top and bottom. Bottom end sump etc to look at water, oil pump and bearings and top and rear for gaskets. Did they do a hot/cold compression test?
 

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How much coolant are you leaking?
Does the car run fine otherwise?
Consider using a "radiator stop-leak" product. I've used them on a couple cars in my life time and the worked fine.
Find a good, independent VW/Audi mechanic. I seems like the mechanics you used were guessing. I don't know why the had to run the engine at 4,500 rpms to do the testing.
 

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Does the car run fine otherwise?
However, they stopped as the engine was 'clattering'
Yes, get a second opinion from a garage that is familiar with the engine and cooling system design. At 56K some V.W engine types need cam belts and water pumps replaced as per the relevant routine maintenance schedule.
 

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Discussion Starter · #5 ·
You don't say what year or engine variant? The older Tdis pre- about 2010 are relatively simple but the newer CR diesels have a lot of added emissions clutter and an EGR cooler located at the back which is an absolute pig to get to and probably involves a lot of labor? 56K is very low mileage and rattles from the engine aren't healthy. Did they check the engine oil pressure? If they put a U.V test dye in the coolant, did they find it in the engine oil?

No internet poster will tell you what exactly could be wrong with an internal engine fault such as yours. Your garage is in a better position with experience and actually looking at the engine. A V.W dealership would probably only fit a new engine at great expense. Unless you have experience rebuilding engines, getting others to do it will be expensive and you never know what you are going to find until you start paying them hourly labor which could be all in vain as they dig deeper.

There aren't enough facts and a diverse range of possibilities to give you a better answer. You could have coolant leaking into and diluting oil causing serious engine problems according to how long the fault has been there? There are several things to check when looking for a coolant leak, where coolant is going and what specific evidence can be found. When cyl. head gaskets fail, the coolant system over time usually pressurises, when coolant leaks into the combustion cylinder, you often see white smoke. When coolant leaks from other places you may find it on the engine tray or floor. Some modern engines share the same water and oil pump drive with seals between the two which can fail causing coolant to mix with engine oil or vice versa because the oil is at a higher pressure.

AFIK the EGR cooler is fed with coolant using hoses or fixed pipes and it might be possible to fit a test bypass? The ECU would after time fault on low cooler temperature, but that should't stop a pressure test being done. Having built many engines in the past and time doesn't cost me, I start tearing down on the basis I have nothing to lose if I have to fit a used engine. But on a low mileage engine like yours with ownership history I might take that chance as a used engine is always a risk. You can start from the top and bottom. Bottom end sump etc to look at water, oil pump and bearings and top and rear for gaskets. Did they do a hot/cold compression test?
Thanks , this is great. I've been considering what you have said.
The car is services by a VW dealership. I'm not a mechanic, so have to consider all actions as costly. There is no white smoke from exhaust. The coolant has been losing for about 3 months ( about 1200 miles ). No puddles under car, nor any exernal evidence detected by the garage ( I guess from obvious pipe junctions etc ). engine is a 2009 model.
I think from what you saay my options are;
  • ask for a bypass test on the egr cooler to prove / disprove
  • forget the cooler leak and ask to investigate / elaborate on the engine clatter. As this would be the bigger issue and it may fix the leak or give opetrtunity to fix at the same time.
 

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Discussion Starter · #6 ·
How much coolant are you leaking?
Does the car run fine otherwise?
Consider using a "radiator stop-leak" product. I've used them on a couple cars in my life time and the worked fine.
Find a good, independent VW/Audi mechanic. I seems like the mechanics you used were guessing. I don't know why the had to run the engine at 4,500 rpms to do the testing.
Lost about 4 litres over 1200 miles so far. Its a slow leak noticeable after a 200 mile drive, as it needs topping up again. The car is services by a vw dealer, so I have to go by their authority. Car runs like a dream... which is why I am in no rush to fix it, despite knowing if I dont, it will cost me in the end. I'm not sure about the 4500rpm test other than s was to get the engine hot, as part of the dye test. Thanks for your input.
 

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Discussion Starter · #7 ·
Yes, get a second opinion from a garage that is familiar with the engine and cooling system design. At 56K some V.W engine types need cam belts and water pumps replaced as per the relevant routine maintenance schedule.
So Iwas wondering if the egr cooler was the only part that might be the leak source , other than the obvoius things a visual check would identify? lLike the water pump - would that be a coolant leak suspect. It would be a shame to replace the egr cooler alone, to no effect
 

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You said you aren't a mechanic, what are you trying to achieve that others with more experience and eyes on can't? You should have gathered by now that unless you can see pools of coolant on the floor, finding the cause won't be easy.

Getting a second opinion from a shop familiar with V.W/Audi/Skoda/Seat engines is my best advice. Where did you get the idea that a water pump problem would always show a visible leak? I thought you said they had done a dye test? If it's not coming out the engine it must be leaking internally? Just like the human body, you can have an external bleed you can see or an internal hemorrhage you can't see, but the end result is the same.

For those that suggest putting stop leak gunge in your car, they've never torn down a modern engine or radiator and seen the consequences of using it. Ask a V.W shop what they think about it. It's not just fixing the leak, it's what it leaves behind. You've never seen inside an EGR cooler or some of the other coolant parts fitted to modern vehicles. I have and I know just how narrow cooling channels are to achieve high efficiency.
 
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