Driving home from work this morning I thought I would plug in the laptop and take some logs.
I had a few parameters up on the screen one was the coolant temp.
I did a WOT 3rd gear pull and all seemed ok,I did get a couple of knock events and backed off at 6000rpm,anyway I carried on my journey and after a couple of minutes I noticed the temperature rising from 93* up to over 100 so started to get worried,looked down at the cars temp gauge and all was normal(just over half way),drove for another 30 seconds to find somewhere to pull over and by this time temps were reading 110* and steam pouring from the engine.
The SUBARU temp gauge still reading normal!!!

I've only had a quick look but water is leaking from the area where the bottom hose joins the thermostat housing. I'm hoping it's just a split hose but I know the water pump is in that area and could be that's failed?

At what temps will the engine and steel head gaskets start to become damaged? The car was only driven a minute at over 100*

If a head gasket fails would I see water pouring out?
AND
At what point does the Subaru gauge tell you the car is overheating? Thankfully I'm running ESL and had my laptop plugged in!

Cheers
Rich

 

It's taken you 8 years to work that out?

You won't see water pouring out if it's done the head gasket.

It lets you know when it's almost boilt itself dry. A bit like the engines fucked oil light.

 

I know it's not a reliable gauge to go by but thought it might have gone up when reaching 110

 

120 it will move again.

 

It's useless. I have a Defi one, the OE one lags it by ages. It only really starts to read after 70 deg. I only left it in situ as I couldn't cope with seeing it constantly at 0.

 

I have a couple of gauges to fit,oil temp and pressure so I will invest in a temp gauge
I'm sure it's not far from goodnight engine when reaching 120+ and before the oem one tells you there's a problem.

 

My water temp was doing 109 when on track and the oem gauge did not even move. I read it before they are set so they only go off when it's seriously high water temp because otherwise everyone will freak out every time they see it moving a bit.

 

This. It simply reads: below operating temp, at operating temp and meltdown imminent. If it ever goes above normal, you'd probably already know there was an issue...

 

Split bottom hose.
Good job I had the laptop plugged in,just hope it's not done more damage!

 

oops, not good, well and good, if that makes any sence lol

 

PSI3 data monitor was great in my old hawk for this. dash temp gauge never really flucuated between 88-98c according to PSI3, and the fans always came on at 96c

 

Welcome to 1995

I said it many times pretty much ALL cars have a temperature gauge like this. And I'll keep posting it until people finally realise that. This is not new It been like this since the Shamen and Prodigy were in the charts and Kurt Cobain was still alive (showing my age)

BMWs, VAGs, Fords, GM, Rovers the lot: The Focus MK1 was the first car I encountered with this style of gauge. I believe the MK1 Mondeo has this, and that pre-dates the Focus by a few years.

The gauge is designed not to move in a temp range of approx 80 to 105 degrees. Above that it will jump from halfway to straight into the red, smoothly..sometimes in a few seconds (Mini, Ford), on some cars it'll just creep up over longer period. The same when its overcooled...on some cars the gauge will still sit in the middle until temps drop to 75degrees, then below that suddenly and smoothly drop to 1/4 on the gauge. The idea is that manufacturers don't want people hassling dealerships because their gauge reads a little higher or lower than someone elses. So the "normal" middle position has a extremely wide deadband. And therefore utterly useless for anything other than telling the coolant is warm....you may as well just place your hand on a heater outlet for what its worth (and hence why many modern cars don't bother with a gauge at all).

Some cars do have "inbetween" stages between cold and hot. 1/4, 1/2 and 3/4. But again, its not linear.

For example I've regularly seen overheating Rover 75s (K-series head gasket...not unlike the EJ25 )....fans on full gauge reading normal...but OBD temp shows 105c...then it hits 106 and bang it goes straight into the red,

If you are concerned about temps and want to monitor them accurately then only use the OBD live data. This will give the exact reading the engine ECU is seeing and providing fuelling for (engine coolant temp is a prime variable in calculating fueling). This, of course assume good coolant flow; an airlock, say from a dodgy gasket or pump sucking air can cause coolant not to circulate around the sender whilst the cylinder heads are overheating.

This is why I always use a laser thermometer to check temps of heads, headers and t-stat housings after performing cooling system work to ensure coolant is flowing.