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How long can I drive with an over heated engine?

kobechu

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Thanks everyone for your replies. Yes it is actually overheating and not just a gauge thing. I know this because I can hear a loud gurgling/bubbling/boiling sound in the left side near the engine somewhere, and sometimes there is a leak of coolant under the car. Sometimes this is a large leak where it basically loses all coolant, but more recently it has only been a small leak.

If the engine is overheating, and two mechanics can't find the reason, suggest you look for a couple more with knowledge.... eg Natrad or similar.
Thanks for this! Didn't know specialists like this existed! Will definitely pay them a visit.
 

immortality

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Bubbling/boiling coolant is an indication of a loss of pressure in the cooling system. Replace the radiator pressure cap with a new genuine unit for starters.
 

J_D 2.0

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Hi all,

Seems like as with many others, I have an engine that over heats at random times, and the cause is unknown. I have had it looked over by two mechanics and neither know the problem. So I have just come to live with it and have spare coolant in the trunk at all times.

My question is, how long can I drive for once the temperature needle hits high and I get a warning that the engine is over heated? Obviously I know I should stop asap but this isn't always possible. One time I was about 1km from home and was wondering if I could just slowly drive home with an over heated engine? Or would the engine blow up?

Also, how long should I usually wait until it's safe to open the coolant cap?
My two cents worth? The ability to drive the car when it’s overheating depends a lot on what the cause is and where you are driving (city or highway). Generally speaking if the car has lost a bit of coolant or the thermostat has stuck shut you can somewhat get around this by turning on the heater if your on the highway with low load and plenty of airflow (speed).

If your accessories belt has snapped and the water pump doesn’t work at all forget about it and get it towed. If your in the city with stop start traffic forget about it and get it towed. If your in a mountainous area where you will be on the throttle a lot forget about it and get it towed.

The heater core is normally further down in the cooling system and will be full of coolant even if the top of the radiator is empty so provided the pump still has some ability to pump coolant around turning on the heater might reduce the temperature sufficiently to make it home.

I‘ve personally done this myself with three different cars. First one was a Subaru Tribeca that cracked the radiator end tank, the second one was my SV6 when the inlet o rings went and I didn’t realise until the the temp started going up (presumably because the pump couldn’t pump sufficient volume anymore as it was partly in air) and the third was with my SSV when the thermostat failed shut. None of them suffered any long term damage.

The important thing is that the temp must go down sufficiently to be kept below the red zone. If the temp keeps climbing or stays in the red zone get it towed.

I know everyone here is going to bang on about blowing head gaskets and hot spots in the head but in my experience this doesn’t happen (at least with my three cars anyway) and I don’t see how it will happen if your gentle with throttle inputs as the available overhead in the cooling system and oil galleries (and thermal transfer in the heads) are made to cope with the cars maximum power output.

For example my SV6 makes 200kw at the flywheel and you only use around 20kw to drive the car at a steady 100kph on the highway so the cooling system capacity required is only 10% on a relatively flat highway. My SV6 was also probably running for a few weeks with hardly any coolant in the top end of the cylinder heads as the o rings would have been leaking for a while and the heads didn’t disintegrate from it (I don’t flog my cars for the most part and rarely go over 3000rpm so this probably has something to do with it).

Again I would like to reiterate that this is just my two cents and my personal opinion and you need to make the judgment call yourself on if your willing to take the risk of doing cylinder head damage from lack of coolant in the cylinder heads vs paying for a tow truck as cylinder head damage is definitely a possibility.
 
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kobechu

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Bubbling/boiling coolant is an indication of a loss of pressure in the cooling system. Replace the radiator pressure cap with a new genuine unit for starters.
Thanks. Do you mean this?

20210116_091611.jpg
 

tml678

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How long before you open the cap ? How much pain can you bear ?
Yep this...

Give it longer than the hour I gave my old VS..trust me, this is a pain you wouldn't wish on your worst enemy..
..07A4E053-226F-46BA-AA34-040D5B341A5C.jpegAFD58558-AFE0-4958-B122-1F49D6A81A15.jpeg
 
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immortality

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Ouch. That's a hard way to learn but hopefully others heed the warning.
 
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tml678

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hopefully others heed the warning.
Absolutely. The top hose was barely warm when this happened. Thought I was safe..nope..I'd go as far to advise people now to only do it on a stone cold engine.

As you say, let my pain be a lesson..
 

kobechu

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you can somewhat get around this by turning on the heater
Why would this help?

Yep this...

Give it longer than the hour I gave my old VS..trust me, this is a pain you wouldn't wish on your worst enemy..
..View attachment 218253View attachment 218254
Ouch, sorry to hear. I actually burnt myself once too, that's why I was asking lol. My engine over heated and I was scared my wife would get the shits with being stuck on the road at 10pm, so I wanted to refill the coolant asap. Opened it and it came bursting out everywhere, the burn on my wrist was exactly the same as yours in the pic. I'm surprised I didn't burn my face. My main concern at the time was the cap had flown somewhere and I needed it to keep driving.

Oh well, at least now I know what coolant tastes like.
 

kobechu

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My engine over heated tonight, made it back home just in time. This time I made a short video. What's hard to see is there is a bit of smoke coming out from near the yellow coolant cap area.

 

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Why would this help?
This helps because you are expelling more heat out of the cooling system than is normally the case with the heater off. It is only a relatively small amount but it can be enough to stop it from overheating.

When the thermostat broke completely shut on my SSV I had just left work 5 odd minutes before hand and the overheat chime/display happened. My drive home is nearly all highway and turning the heater on bypasses the closed thermostat and gave me enough cooling to pull it back out of the red zone and get it home.

It was a 35 degree day so it wasn’t pleasant at all driving in hot weather with the heater going full blast but it got me home! Interestingly enough the oil temperature gauge (the factory one in the dash) said the oil temperature only rose from its normal 108-110 degrees to 120 degrees by the time I got home (about a 20 minute drive on the highway) so the temperature rise suffered by the engine itself wasn‘t that great.

My engine over heated tonight, made it back home just in time. This time I made a short video. What's hard to see is there is a bit of smoke coming out from near the yellow coolant cap area.
If you haven’t replaced your coolant cap before do it because it will be fuked, guaranteed. I just had to replace the caps in both my SV6 and SSV when I had to do coolant system work on them as the o rings perish and stop them from containing any pressure as soon as you remove them and break the seal. They are basically a disposable cap!

If you’ve already replaced the cap then it sounds like you have a blown head gasket between the water jacket and the combustion chamber. This will over pressurise the cooling system and the only place that excess pressure can go is through the overflow tank.

The easy way to tell if this is the case is to refill the cooling system when it’s stone cold (to reduce air space in the cooling system) and start the engine from stone cold. Check the pressure by squeezing the top radiator hose. If it builds up pressure and the hose goes hard well before the temperature goes up then the head gasket is probably blown. You would need to verify with a compression test after but this is normally a good first step to see if it has blown the head gasket to the water jacket.
 
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