Coolant Issues - Is It Serious?

[adam.w]

I bought a 996 a few weeks ago. I noticed that the coolant looked a bit dirty and took it to a mechanic. He said that the coolant has combustion products. He was worried about a cracked block or headgasket and wanted to do more tests. The car has ran fine. I drove it 2,000 miles with no problems. Previous owner said it was fine, but he did mention topping off the coolant a few weeks ago. There is no coolant in the oil from what I can tell. Car does not smoke. And really nothing wrong except that the coolant has a few black specs - doesn't look like oil, but more like dirt or black flecks.

Mechanic did a leak down test and looked at each cylinder with a camera. He said he couldn't find anything wrong. He said that one spark plug looked like it had coolant on it because it was white. I could not appreciate that. The tubes were also melted. I found out that the car overheated because of water pump failure 20,000 miles ago. But hasn't had problems after that.

After I drove it from the shop, I got a low coolant indicator. After filling with distilled water and driving further, I got a check engine light. I drove 600 miles on a road trip and the car drove fine with no problems other than the check engine light still being on. I refilled the gas, but light is still on.

Does anyone know what might be going on? I will be taking it to another shop to get the check engine light looked at and another opinion on the coolant residue.

[Loren]

Check your oil for coolant it will look like a chocolate milk shake.

Check your coolant for oil.

If you can't find the problem externally you may need to pull the engine and pull the heads off. But I wouldn't do that unless I was pretty sure there is a problem. So get a second opinion.

[wvicary]

The impeller on the water pump is made out of black plastic. When the brng starts to fail the impeller will rub against the engine block which could be the cause of your black flecks. I would remove the belt and inspect the pump.

[adam.w]

Check your oil for coolant it will look like a chocolate milk shake.

Check your coolant for oil.

If you can't find the problem externally you may need to pull the engine and pull the heads off. But I wouldn't do that unless I was pretty sure there is a problem. So get a second opinion.

I can't appreciate any oil in the coolant or coolant in the oil.

[adam.w]

The impeller on the water pump is made out of black plastic. When the brng starts to fail the impeller will rub against the engine block which could be the cause of your black flecks. I would remove the belt and inspect the pump.

The water pump was replaced 20,000 miles ago. Car doesn't overheat now. Is it possible that the water pump would fail again?

I think I am loosing very small amounts of coolant somewhere, but can't see any leaks.

[adam.w]

This morning I looked at the coolant again when the car was cold. When I opened the cap, coolant started to leak out. It appears that I overfilled the coolant this weekend. The cap is what allows excess pressure to escape, right? I looked at my cap and it ends in 0.

Also, the black residue seems to be coming from my cap. Does this make sense?

I have the black coolant cap and from what I read that is an aftermarket part.

Edited May 2, 2010 by adam.w

[Loren]

Your coolant cap should 996.106.447.03 (or newer). For only $21.05 MSRP I would replace it and take it out the possible faults.

[Ahsai]

This morning I looked at the coolant again when the car was cold. When I opened the cap, coolant started to leak out. It appears that I overfilled the coolant this weekend. The cap is what allows excess pressure to escape, right? I looked at my cap and it ends in 0.

Also, the black residue seems to be coming from my cap. Does this make sense?

I have the black coolant cap and from what I read that is an aftermarket part.

There's a black rubber gasket on your old cap. Maybe it's crumbling. Hopefully, that's where the black residue came from.

[adam.w]

Thanks for the input, guys. I have some pics:

I'm definitely ordering a new coolant cap, but just wondering if anyone knew what was going on.

[adam.w]

Any thoughts on the pics? Is the black residue coming from the coolant cap rubber?

[Loren]

Looks like the cap to me.