Overheat detected in time, I hope

[mogindo]

Here is a short story.

Driving down the express way, the temp gauge goes past the normal horizontal, and climbs upwards. I stop.
Open the cap, and the coolant is steaming out, very hot and a lot of pressure.
The top radiator hose if rock solid (like a big pressure buildup there). I ran the heater, but not hot air coming out. (looks like no coolant circulation)

I waited for the engine to cool off a little and limped down the exit ramp 1km away. The temp climbed past the top white line on the gauge, but never went into the red zone. (of course the exit ramp was an incline :((

I stopped, opened the cap on the reservoir, and let the steam and the pressure out. There was a lot of coolant that came out very hot.

First thing I did was to take the thermostat out. It worked. Engine temp was back to normal and everything seems fine. The thermostat was only 4 months old (or my mechanic never changed it when I instructed him to do so).

Now the question is....how much damage has that done to the engine? Maybe I am too sensitive, but it seems to work a bit louder and rougher.
I also checked the top hose on the radiator yesterday and it was very hard again. But softened when I opened the reservoir cap.

Any thoughts?

[loanrangie]

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.

[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 :((

[steelo]

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 :D

[mogindo]

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 :D

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).

[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.

[mogindo]

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?

[Blknight.aus]

not with a rock solid hose he doesnt...

my moneys on a head gasket failure.

[mogindo]

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?

[zealand]

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?


Head failure
A few things but not limiting it solely to
1: Water in the oil - can be seen as a milky color on the dipstick
2: Oil in the water - can be seen in overflow bottle or radiator
3: Water blowing out of the exhaust tail pipe
4: Steam blowing out of the tail pipe
5: Gasket blown between cylinders causing combustion gases to enter cooling system which in turns over pressurizer the system and that then dumps the excess water out

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

Never ever open the cap on a HOT engine
1: Water boils @ 100 deg c Most engines run @ 90 deg c thermostat opens approx 80 - 85 deg c the only way they can maintain this is to pressurize the cooling system which will increase the boiling point of water,
very approx 120 ++ deg c
If you open the cap when the engine is hot the water will want to expand rapidly as soon as the water meets atmospheric it will be not just under pressure but also under the physics of law which is the above equation
so it blows out and up from the bottle at the operator at extreme temperatures and pressure usually hitting the person in the face - arms - chest,
The water will be so hot it could take your skin clean off and you will spend quite some time in hospital,
Ive seen this happen to quite a few people over time, [mainly from people I have come across at the side of the road]

I go along with Blknight.aus the chances are a blown head gasket across one or more combustion chambers, but a seized thermostat will cause very similar results as you said
" that there was NO circulation also no heat when I turned the heater on "

Have the engine tested by a good workshop it will only take them a short while to test things out, better safe than very sorry.:cool:

[disco2_dan]

Possibly warped head or head gasket, also just because the temp gauge didn't reach the red doesn't mean the engine hasn't over heated! As soon as that gauge moves from its normal position pull over and turn the engine off! By the time you get to the Red it can be waay to late! Especially if your already lost some coolant! Hopefully it's just the thermostat as that's a lot cheaper then rebuilding a motor! But if your still getting a swollen tight top hose with no/replaced thermostat then my guess is a gasket! Best of luck buddy

[mogindo]

Thanks for your contributions and the analysis. All put together really makes sense, especially the last comment from Disco2_Dan that summarized all of the above comments. Oh, boy, so now I need to have my engine checked. Let's hope it was just the termostat and the swollen top hose (after the incident) was just temporary. I may have put too much water into the system, I need to check the coolant levels again and monitor the top hose for hardnes. (and go to the shop to check my engine).

What I am a little (of a lot) upset with is that I had requested my mechanic to replace the thermostat 4 months ago, and in my view that should not fail, but it did (and may have screwed up the gasket). So maybe he didn't replaced and just told me he did. I should have done it my self, grrrrr....

[Blknight.aus]

http://i2.photobucket.com/albums/y20/Aussie110/Coolant%20Alarm/CoolingSystem.jpg

heres the flow diagram for the tdi, coolant flow through the heater is not dependant upon the thermostat opening.

On that note you shouldnt be able to force the thermostat open, without any heat its going to be held closed by the wax pellet.

if your heater worked before you cooked the engine and it isnt blocked or internally bypassing now then the problem is coolant flow related. check out the position of the heater hoses and the normal direction of flow (unlike the td5 it doesnt change direction at any point) and see if you can tell us why the heater stops working very early on in a low coolant situation. now would reversing the flow direction make that any different.

now for extra credit.....

note that the location of the temp sender is up on the thermostat region and they dont work as well when they are not immersed in coolant. Given the hieght of the outlet for flow into the heater matrix how much circulation would there be through the head by the time that

a, effective flow through the heater matrix ceased
b, effective flow past the thermostat and therefore the temp sender ceased?

[mogindo]

UPDATE:

Engine was inspected by my mechanic, compression and gasket are all fine.
IT SURVIVED!!


Thanks to all for your contributions!

[SLOWBOAT]

Great news for you. Now for the the other issue of no flow eh?