Thread: Overheat detected in time, I hope

Sounds like the typical head gasket failure, worst thing you can do is open a cap on an overheated engine while still boiling hot.
What colour is the overflow bottle, black tend to split and the upgraded ones are a white/opaque colour.

The overflow reservoir is black, but it hasn't split or anything.

Can you please help me understand your statements:

1. Why do you think that this was a typical head gasket failure? (truck drives fine, does not smoke, does not leak anything. I always though that if head gasket fails, there would be white smoke or something)

2. Why the worst thing you can do is open a cap on an overheated engine? (whats the principle behind this?)

I guess I really don't want to hear the "head gasket" in the sentence (

Originally Posted by mogindo

The overflow reservoir is black, but it hasn't split or anything.

Can you please help me understand your statements:

1. Why do you think that this was a typical head gasket failure? (truck drives fine, does not smoke, does not leak anything. I always though that if head gasket fails, there would be white smoke or something)

2. Why the worst thing you can do is open a cap on an overheated engine? (whats the principle behind this?)

I guess I really don't want to hear the "head gasket" in the sentence (

Not to sure about no.1 but no.2 usually means that after hot coolant has flowed out there's nothing (or next to) in the motor including pressure, just hot metal which warps. If you then put cold coolant in, cracked metal somewhere in motor or gaskets, try putting cold water on a hot fry-pan straight off the stove you'll see what I mean.
Just my understanding from over the years

Originally Posted by steelo

Not to sure about no.1 but no.2 usually means that after hot coolant has flowed out there's nothing (or next to) in the motor including pressure, just hot metal which warps. If you then put cold coolant in, cracked metal somewhere in motor or gaskets, try putting cold water on a hot fry-pan straight off the stove you'll see what I mean.
Just my understanding from over the years

Well, I think I did OK in this department, as it took me a while to take my tools out and take out the thermostat. I think it was close to an hour before I started to pour water back in (only coolant I could find). The bottom bolt gave me a bit of trouble, so I think the engine cooled off significantly in that time.

In my mind letting the pressure out was the only way for me to get to the thermostat as there was a big pressure buildup in the top radiator hose. Opening the cap released the pressure.

Letting the engine cool down too quickly initially, (by letting the pressure off) could have been an issue I understand, but the temperature outside was 34C anyways, so it wouldn't drop like a rock.

My question is that there is pressure build up in the top radiator hose NOW. And of course I am paying attention to this only after the incident. I am just not sure if that's normal or not. And I am trying to determine if I should worry at all, or just as I said, I merely missed the overheat. I may replace the water pump just in case. (taking all of the above in to the consideration, the engine seems OK, I haven't lost power and its not smoking, so I don't know).

You said it seemed to be working harder, if you read thru the tdi gasket failures here they are quite often between cylinders and not necessarily directly on a coolant passage .
Releasing the pressure is one thing but you could have lost all the coolant and seriously injured your self at the same time.
You could also just have a faulty reservoir cap.

Originally Posted by loanrangie

You said it seemed to be working harder, if you read thru the tdi gasket failures here they are quite often between cylinders and not necessarily directly on a coolant passage .
Releasing the pressure is one thing but you could have lost all the coolant and seriously injured your self at the same time.
You could also just have a faulty reservoir cap.

Good point about the inter-cylinder failure. Hmm, I think will keep an eye on it, but keep the extra gasket at home for now. (I have one The loss of power (if there) is not dramatic.
So I think I just might have avoided the overheat...?


(I have waited for it too cool down a little, and I had work heavy duty gloves, so no worries. I'll take that point too regardless.
I filled up about 4.5 litters of water back into the system, so it wasn't entirely empty, but certainly more than I expected it to be. (tdi 300 auto takes 11.7 ltrs)

Now, what are the symptoms of a faulty reservoir cap?

not with a rock solid hose he doesnt...

my moneys on a head gasket failure.

OK, thanks all for contributions. Its not a good news for me, a kind of really sucks if it is the head gasket.

From what I understand the temp increase was due to a stuck (broken) thermostat, because when I removed it everything went back to normal. I tried to open the thermostat by hand and it would not let go until I preyed a screwdriver in there with a lot of force.

There was no circulation, which explains the hard hose and pressure, but also no heat when I turned the heater on.

I still don't understand, why it happened and how?
Can you give me more detail to the process of head gasket failure?