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200Tdi coolant leak - now I'm stumped


Tetsu0san

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Hi all

I recently found a leak in the gasket behind the timing chest on my 200Tdi, which I repaired. I replaced all the gaskets and did a cam belt change at the same time and all looks good. No more leak from here, but I am still loosing water, and it seems to be loosing water quicker than before.

Does anyone have any other ideas as to where the leak could be coming from, or anything else I can look at? I am going to try to pressure test the system at some point if possible, but there are no drips or obvious water lines anywhere that I can see. The water system doesn't pressurise and there is no white scum in the oil, although I am not ruling out a head gasket problem.

One extra job I did at the same time as all this was to clean out the fins on the radiator as it was very clogged up with mud. I suppose this could have also exposed a leak or made the leak worse, but there is nothing obvious from here either.

Help!!!

Cheers

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Usually the antifreeze will leave 'furry' coloured stains [blue, yellow or red depending on the coolant used] at any leaks.

You can also get an ultraviolet-fluorescent dye to add to the coolant to trace leaks: this glows bright blueish-white under UV light.

My last coolant-leak was in the heater matrix. UV-dye didn't reveal it, the 'nasty niff' when you turned the heater-blowers on did.

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Ah, heater matrix. That is a possibility I suppose. I was seeing little puddles in the footwells after it rained which I put down to a leaky windscreen or sunroof, but it never seemed to appear on a warm day.

Again, I am not seeing any telltale streaks anywhere so I am a little stuck.

Has anyone heard of a cracked block or leaky cylinder on a 200Tdi? I don't think they are wet lined so I presume I can rule this out?

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Has anyone heard of a cracked block or leaky cylinder on a 200Tdi? I don't think they are wet lined so I presume I can rule this out?

Not sure about a 200, but have seen a crack from coolant jacket to intake port on a couple of 300tdi heads. One had no symptoms at all except for losing around 1L of coolant every 100 miles. The other had a rough idle starting from cold, eventually it started dropping enough to occasionally lock a cylinder when cranking.

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My old 300Tdi had a cracked head which caused pressurising in the water system. I think that if I can't find the leak after a pressure test it's going to be head off and have a look.

What about cracked blocks? Anyone seen anything like that?

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Once had an annoying leak on a Lada, turned out to be a small split in the pipe that went from the engine to the heater it was directly under the pipe and only when it was really hot but it evaporated almost instantly it hit the engine.

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The strange thing is that it only seems to lose water when it has been sat for a while. If I drive it every day, or every other day it seems OK. But leave it for a week or so and there is a loss of about an inch in the header tank.

Once I get a pressure test done, I should know more. Or at least know if I need to remove the head :unsure:

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A little update and I think I need some more advice.

I went out to start the Disco this evening, and to cover the engine in talc (to help see the water leak) and when I started the engine it seemed to run very lumpy. It idled OK, but when you rev it it seemed to misfire a little. There was also a lot of white smoke that came out the back while I was revving it. This soon cleared and it ran better, but not perfect. There has always been a little puff of white when you start her up, but not quite as much as this.

To me, this sounds like what TSD was saying about a leak into one of the cylinders which causes it to run rough when cold.

Any other thoughts before I strip off the head?

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