Engine fan on constantly

skiddlydiddly

Lokolo wrote: »

Sounds about right (the water pump anyway), makes sense anyway.

Water is constantly being rotated through the engine to cool (water is a liquid which takes longer to heat up/cool down). If its at 100c that's bad as water evaporates at 100c!!!

The fan aims to cool water as it passes it.

This then goes around the engine taking heat away from various parts.

I think that's how it works!

If the water isn't being pumped around but staying still, the water just keeps heating up and never passes the fan 'junction' to cool.

It does if it has somewhere to evaporate too, it can go higher at different pressures before evaporating.


It does sound like it could be the pump/air in the system, both could cause this.
Have a squeeze of the top water pipe of the radiator, you can normally tell if its full of water or has air pockets by how squishy and warm it is(bottom hose warm and top cold prob means an air pocket).If you do have air pockets then there's usually a bleed screw to let ai out while you put new fluid in or if you cannot find it then keep squeezing the rad pipes while you fill it up.You will see bubble of air coming out as you do it if you through the hole you fill it up.

cyclonebri1

Lokolo wrote: »

Water is constantly being rotated through the engine to cool (water is a liquid which takes longer to heat up/cool down). If its at 100c that's bad as water evaporates at 100c!!!

A bit wrong there I'm afraid.

Water evapotates at any temperature, it forms steam at 100C although it's higher than that in a car engine as it is pressuried during heating.

Also water is actually used for it's ability to transfer heat quickly not slowly, a very differnt quality to air cooling. ;)

scullster

cyclonebri1 wrote: »

A bit wrong there I'm afraid.

Water evapotates at any temperature, it forms steam at 100C although it's higher than that in a car engine as it is pressuried during heating.

Also water is actually used for it's ability to transfer heat quickly not slowly, a very differnt quality to air cooling. ;)

Someone talking sense about water at last. An engine cooling system is a closed system hence why it shouldn't need topping up.

Look up steam tables (http://www.engineeringtoolbox.com/saturated-steam-properties-d_101.html) - on a typical day under atmospheric conditions (P=101kPa), water boils at 100C. In a pressurised system, say at 202kPa (or 2atm) the water will not boil until approx 120C.

This is one of the reasons why they tell you not to remove the filler cap when the engine is hot. Say your water pump was faulty and the coolant temperature had crept above 100C, it probably wont be boiling. But open the cap, you immediately drop the system pressure to atmospheric and the coolant could instantly boil off, a bit like an uncontrolled steam generator.

vaio

scullster wrote: »

Someone talking sense about water at last. An engine cooling system is a closed system hence why it shouldn't need topping up.

Look up steam tables (http://www.engineeringtoolbox.com/saturated-steam-properties-d_101.html) - on a typical day under atmospheric conditions (P=101kPa), water boils at 100C. In a pressurised system, say at 202kPa (or 2atm) the water will not boil until approx 120C.

This is one of the reasons why they tell you not to remove the filler cap when the engine is hot. Say your water pump was faulty and the coolant temperature had crept above 100C, it probably wont be boiling. But open the cap, you immediately drop the system pressure to atmospheric and the coolant could instantly boil off, a bit like an uncontrolled steam generator.

I seem to remember most rad caps are 7 psi so that moves the boiling point up to about 110 degrees but, as you say, it will flash to steam if you take the cap off when it's hot

gazfocus

Thanks for all the comments so far. So, I was meant to get my car back today - phoned the garage at 4:30 and they told me that they suspect the head gasket has gone.

I managed to find the phone number of the guy that ran the garage and spoke to him on the phone. He told me that firstly the car only had a 28 day warranty because it was under £2k and he said that because I'd authorised another garage to repair the water pump he is not accepting responsibility for the head gasket - he also says they've gone out of business and he is selling the remaining cars from his house.

Can anyone please offer any advice? I've only done 103 miles in the car since I bought it, the guy knew it was my first car and I think he's just taken advantage.

vaio

gazfocus wrote: »

Thanks for all the comments so far. So, I was meant to get my car back today - phoned the garage at 4:30 and they told me that they suspect the head gasket has gone……..

Have they done tests or are they just changing parts till the problem goes away? How did they diagnose the water pump? And the head gasket?

gazfocus

vaio wrote: »

Have they done tests or are they just changing parts till the problem goes away? How did they diagnose the water pump? And the head gasket?

They did tests to diagnose the water pump and when they fitted the new water pump they did a pessure test and other tests and found the head gasket to be a problem

Pew_Pew_Pew_Lasers!

It isn't surprising that the HG is weak, considering the car has likely been overheating for some time.

Expensive lesson. Car ownership is like this.

property.advert

Pew_Pew_Pew_Lasers! wrote: »

It isn't surprising that the HG is weak, considering the car has likely been overheating for some time.

Expensive lesson. Car ownership is like this.

No, bangernomics is like this and it certainly isn't helped by a rogue trader who just takes the money and runs. No wonder the motor trade has such a bad reputation.

vaio

gazfocus wrote: »

They did tests to diagnose the water pump and when they fitted the new water pump they did a pessure test and other tests and found the head gasket to be a problem

I'd have thought a head gasket failure that causes overheating and shows up on a pressure test would be combustion products into the water system and have been instantly obvious to a mechanic by virtue of the steam spitting out of the header tank or even a simple sniff test.

Think you might struggle getting the dealer to pay given you didn't give him a chance to fix it and took it to a garage that diagnosed a pump and then when that didn't cure it now they say head gasket. The dealers argument will be that a. you should have informed him before doing anything and b. you have taken it to somewhere that didn't diagnose it properly thus incurring extra labour costs.

I think to stand a good chance of winning you need a valid excuse for not talking to him first plus an professional independent report detailing the faults.