The dreaded temp gauge red light...

[hogweed]

Originally Posted by suzublu

Fit a digital temp gauge, lifesaver

Sorry for the thread hijack, but... should I/is it even possible on my TF?

[Steve1966]

Hi Simon, I’ve managed to get home ok. Temp initially rose to 99 before dropping back and cycling 92-98 ish again. After 15 miles this had stabilised to 90-95, usually hovering around 93. So, perhaps things have settled down. Bottom hose is cooler than top. Just checked level and it’s fine again. I’ll run with the OBD on for a few days (weeks) but it might just have taken one of those enormous gulps you hear of (probably IMG related) and that’s it. It did misfire particularly badly this morning on start-up. I’ll check the level again in the morning.

EDIT: I forgot to mention that I managed to remove the clip on the air bleed/jiggle valve hose top left of the head before I left work (company scissors..). I wonder if the hose is blocked with K seal as I’ve noticed a hiss before when removing the hose after re-filling the system. This may account for the improved temps on the journey home.

[SD1too]

Originally Posted by Steve1966

Bottom hose is cooler than top.

The temperatures you've mentioned are ok so long as they don't rise above 104 degrees approximately, but the bottom hose should feel almost as hot as the top hose. If it's distinctly cooler then your thermostat may be stuck partially closed (K-seal?) or there's a blockage in the radiator, so don't lose any sleep over it will you!

Simon

[Comfortably Numb]

Worn/corroded/ineffective water pump?

[Steve1966]

Originally Posted by Comfortably Numb

Worn/corroded/ineffective water pump?

It was fitted May 2013 (65k miles ago) so that is a possibility.

[Steve1966]

Currently waiting for the RAC. Temp rose to 100 then dropped a tad then rose and after 5 miles had hit 117 and rising. Parked up in my local golf club..I’m assuming stat not opening as bottom hose and rad cold. I flushed rad a few months ago so it shouldn’t be blocked and the journey home yesterday was fine.

[SD1too]

Originally Posted by Steve1966

I’m assuming stat not opening as bottom hose and rad cold.

Agreed; that's the first thing to check given the symptoms.

Simon

[Steve1966]

Towed home and now having a look at the car. Before I tackle the thermostat can someone just confirm that the following symptoms aren’t pointing to a water pump that is underperforming?

First I checked the bleed screw in the bottom hose. Steady stream of water straightaway so all seems good. However, when the engine is at 90+ temps the inlet hose to the heater is still only warm but the outlet is hot. The heater blows cold but as soon as the revs are increased to say 3000+ the heater blows hot air and quickly checking the pipes they are both hot. The inlet pipe soon cools, and the heater soon blows cold. The radiator and bottom hose remain cold throughout. I thought the heater should be hot during warm up and before the stat opens so a stuck stat shouldn’t affect this whereas an underperforming water pump may, and may also be the cause of the cold rad?

[SD1too]

Originally Posted by Steve1966

... can someone just confirm that the following symptoms aren’t pointing to a water pump that is underperforming?

In my experience Steve, water pumps don't "underperform". They might leak, but the impeller will keep turning at the speed it's driven by the engine.

You should check your thermostat without delay. If it's not properly opening all sorts of strange effects can occur. We're talking about fluid dynamics here which is a horribly complex and highly academic subject. So try to resist too much analysis and theorising. It's time to put on your overalls and get some oil under your fingernails!

Simon

[Steve1966]

Originally Posted by SD1too

In my experience Steve, water pumps don't "underperform". They might leak, but the impeller will keep turning at the speed it's driven by the engine.

You should check your thermostat without delay. If it's not properly opening all sorts of strange effects can occur. We're talking about fluid dynamics here which is a horribly complex and highly academic subject. So try to resist too much analysis and theorising. It's time to put on your overalls and get some oil under your fingernails!

Simon

Don't worry I won't be using the car until it's sorted. It's my only car but luckily I have a number of motorbikes I can use for work. I only asked about the water pump because that leads to more expense as the belts are due in May when it would have been changed anyway but I was tempted, as she is nearing the end of life, to risk leaving the belts and thus the water pump next year. I'll get a stat and change it with the IMG (makes the job easier with the manifold off at least). If it's possible to reach the impeller with the stat out I'll see if it is turning independently of the shaft. I wish this had happened last week before the £400 was spent at the MOT. The biggest irony is that the MOT wasn't even due but I was sick of trying to get parts over Xmas so I brought it forward 6 weeks..