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2005 Passat B5 2.8l V-6
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Bought a used 2005 Passat V6 with 78k miles on it. Very very poorly maintained and needs a paint job but I think it has a lot of life left in it. Really bad mechanics have been at this car based on the number of missing and broken screws just getting it into radiator service position. Anyway, I just started to dig into changing the timing belt on this pig and when removing the block drain plug, of course, nothing. Pushing a wire on up into the hole is not enough to do anything other than create a very slight super dark ugly brown dribble. There was what appeared to be a mix of red and green antifreeze in the system when I bought the car. I got that straightened out, or so I thought. The color of the coolant in the tank has been normal for the last 20K. Recently restored the heat by back-flushing the heater core with water and replacing the temperature control motor (combo problem). Anyhow, I am going to put the car back together to run the engine (of course, with the newly cleared heater core bypassed) trying a chemical flush called Ironite ThoroFlush. I want to use it with all the old cooling system parts installed so as to not ruin the new cooling system components that are going in with the new timing belt. I read that this stuff is pretty strong but might just actually do the job. I discovered a lot of "cholesterol" in the old hoses too so I am flat out replacing those as well. So, after all that .... The question is ..... Can air and/or water be blown backwards into the block drain to maybe loosen and free up that gunk in there before using the chemical flush without damaging or plugging anything else up? Does anyone understand and know the construction of those coolant flow channels enough to answer this? Thanks a lot.
 

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I see no problem with blowing air/water into the drain hole, with the reservoir cap off.
I have the upper and lower hoses off now. I am just worried that I will blow that gunk somewhere else that it shouldn't be. Thanks.
 

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Introducing compressed air into the coolant system can be done safely as long as you don't instantaneously blast 90 PSI into it.
Remember, coolant hoses are only good for about 20 or so PSI.
Remove coolant reservoir cap for sure.
The (2) things I would take caution with are the little coolant hoses that go from the hard pipe (rear of engine and under intake manifold) to the throttle body and the passage through the throttle body itself.
There is also a rear crankshaft seal cover plate that has oil / coolant passages behind it. Not that it'll blow off the back of the engine or anything like that, but the coolant in that area doesn't flow very fast. You might get a coagulated chunk of goo trapped in that area.
 

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If you've never had the engine out or haven't seen the rear side of the V6 engine...


Here's the rear of the engine.
100247




Inside the blue area is coolant, inside red area is oil.
100248




Close up view drain plug at arrow.
100249




Rear crankshaft seal cover plate.
100250
 

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I had the same issues on mine, mixed coolant and clogged drain plug. I flushed the motor out with a hose through the open water pump housing, but never cleared the drain plug. I never had a plugged heater core though and the replacement coolant was fine over the next 10 years that I ran the V6.
 

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2005 Passat B5 2.8l V-6
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Discussion Starter #7
If you've never had the engine out or haven't seen the rear side of the V6 engine...


Here's the rear of the engine.
View attachment 100247



Inside the blue area is coolant, inside red area is oil.
View attachment 100248



Close up view drain plug at arrow.
View attachment 100249



Rear crankshaft seal cover plate.
View attachment 100250
Really, Thank You so much for the info and the pics, very helpful to know what it looks like in there. I took my '98 Passat V6 to 337k mi. I never had any of the problems that I have discovered on this car and those issues that people write about with the cooling systems on their V6 Passats. I believe that proper and timely maintenance is the key and fix what is broken. I have found that the single biggest challenge to owning a Passat is finding a mechanic to work on it. Even 'factory trained' mechanics at dealers have messed up my car more than any others. Another example of poor maintenance on this car; As I moved the power steering cooling tube out of the way it sprung a leak at one of the hose clamps. Honestly, I have never seen power steering fluid that looks as nasty as what leaked out. Just means more work for me. Haven't figured out if the tube is cracked or just a loose factory clamp. Anyway, cheers for the great help. I think I may just inject a bit of cleaner backwards into the hole to help.
 

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2005 Passat B5 2.8l V-6
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I had the same issues on mine, mixed coolant and clogged drain plug. I flushed the motor out with a hose through the open water pump housing, but never cleared the drain plug. I never had a plugged heater core though and the replacement coolant was fine over the next 10 years that I ran the V6.
Thanks a lot. Promising info. Like I wrote, the coolant in the tanks still looked normal even with the blockage. I hope I don't muck it up and make it worse.
 

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there is a distinct possibility , since there is evidence of "two" different coolants being introduced into the system, that there was at some point in time, a coolant leak, and they or their "mechanic"possibly "fixed it" using a "stop leak" product. Using the wrong coolant is telltale evidence that that somebody did not know what they were doing.
 

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there is a distinct possibility , since there is evidence of "two" different coolants being introduced into the system, that there was at some point in time, a coolant leak, and they or their "mechanic"possibly "fixed it" using a "stop leak" product. Using the wrong coolant is telltale evidence that that somebody did not know what they were doing.
Hmmmm. Possibly a factor as well that I didn't think about. Of course, I am hoping for the best clearing the block drain. There was a slight dribble of something coming out while sticking a wire in there. I don't think that this radiator is original so it is possible there was once a leak, (not to mention the clear mixing of different antifreeze solutions). The only reason that I am discovering all of this is because there are no service records for the car and wasn't sure if the timing belt had ever been replaced. After digging in, by way of visible damage and missing screws, I did find that the radiator was put into service position previously even though there was only 78k on the engine. (The owners manual recommends the timing belt at 110k). Even the wheel well covers on this car were damaged by a bad mechanic trying to remove the front bumper cover. Thanks for the insight.
 

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(The owners manual recommends the timing belt at 110k)
That's a pretty ambitious statement.
More like every 70 to 80k miles.
Remember, that timing belt and it's pulleys / rollers are mission critical. Prolonging the change interval is dangerously risky.
 
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