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[Webby the Bear]

thanks for the tips guys ill remember that. Re which pump it is I'm fairly certain that this is the ford one. Sadly i cant get pics of the clit one as we put it back on ha ha :-)

[Webby the Bear]

Good evening chaps, very sorry for the delay.

I think we pretty much covered the lubrication side of things.

We have moved on now to....

COOLING

Firstly i have loads of photos but again my phone isn't sending  really gotta get a new phone.

The purpose of the cooling system...

1. to ensure no overheating
2. to ensure no over cooling
3. to maintain normal and correct operating temperature.

Firstly lets look at the radiator and its function...

in short when you start your car from cold the only coolant moving around the engine is in the water jackets in the block. this is moved about by the water pump and the pressure placed on the coolant.
once up to temperature the thermostat opens allowing coolant to not only flow around the engine but most importantly moves the (recently) hot coolant from the engine to the radiator where it is cooled and then thrown back in to the engine.

it works like this:

1. conduction - heat travels from the cylinders in to the coolant by conduction (heat movement through a solid object).
2. convection - the heat then travels through the coolant en route to the radiator
3. radiation - the coolant enters the radiator hot. it then gets cooled through the radiator by the air coming in from the grill (or by the cooling fan during idle).

our first practical was to drain coolant and refill... piece of piss

you jack it up, brake loose the top hose (to let air in to help with draining), brake loose the bottom hose (or drainplug like in the case of the omega), all hoses back, fill her up, run the car with a few revs, wait for the bubbles to subside. DONE.

The second thing we had to do was remove the rad. ive done 3 now and have to say its a piece of piss also. generally speaking you drain the radiator of coolant, undo (normally 2 monting bolts from underneath, pop it loose from its rubber grommets. DONE

Third thing we did was to test the coolant for its percentage of antifreeze using a hydromoeter. simply press the pump and draw in some coolant from your expansion tank (if you have one) like a syringe and the amount of discs in the tube that float indicate the boiling point of your mixture. we then have a nice graph we can look at which shows what the various boiling points are compared to the exact percentage of antiofreeze mixture. 50% is what you want. not from a ''how low can you go'' chart in terms of temperatuure but also it needs 50% to help with the other things that the mixture does which is stopping rust and corrosion on the engine.

fourth thing we did was to test some thermostsats. this was well easy. take off your thermostat (generally found by trailing back the upper hose to where it meets the engine), put it in some water in a saucepan and put it on the heat. we luckily had a ''thermometer gun'' which we pressed a button towards the water and it magically took the temperature. awesome! anyway on the stats they generally have a number that is the temperature that they're supposed to open at. example, our first one said 89. so that meant it should open at 89oC. when tested ours started to open at 80oC. Bad stat and would need to be replaced as its opening early, causing over cooling and therefore wouldnt get to temperature (or would take too long).

an interesting side note on the thermostat talk is the housing. made of the most brittle material in the world. i only nipped mine up and i broke the housing mended it with a made gasket out of some gasket paper  and some proxy glue which properly stinks of actual shite!!!! horrible. and i still smell of it even after a shower 

finally we came to do a pressure test to look for coolant leaks. only had a quick demo of this but we found that the stat was leaking following me breaking it  obviously the gasket didnt work 

anyway, as i said im sorry for the very very late update but above is what ive done in a nut shell.

i am desperately trying to add my photos as i feel they add a lot to what im doing and trying to say at the same time.

love car bear

[omega3000]

we found that the stat was leaking following me breaking it   

 

[Marks DTM Calib]

1. conduction - heat travels from the cylinders in to the coolant by conduction (heat movement through a solid object).
2. conduction - the heat then travels via the coolant en route to the radiator
3. radiation - the coolant enters the radiator hot. it then gets cooled through the radiator by the air coming in from the grill (or by the cooling fan during idle).

Corrected that for you, you wont see a convection cooling system these days.

The coolant is used as a transport medium for the heat, it effectively stores it temporarily whilst its moved to the radiator.

Also note that hydrometer testing of coolant only tells you half the story as it indicates only the freeze point. One of THE most important things that antifreeze has is an anti corrosion additive that protects the cylinder head, head gasket etc from corrosion.

Bottom line is if its 2 years old (basic stuff) or 4 years old (advanced stuff) then it MUST be changed no matter what the hydrometer reading says

[Webby the Bear]

thanks mark. Very clear as usual :-) re the convection, would the coolant being a transfer medium effectively be convection? The problem i have is that although these are basic terms for most sadly i havent done any science in years and am having to do extra research when we get a new term quoted at us. By th way i Havent really gone in to too much detail on the pressure in the system. I'll try and add that tonight as this is very important :-)

[Marks DTM Calib]

In answer to the convection, no not really is the answer, have a little look at this:

http://www.wisc-online.com/Objects/ViewObject.aspx?ID=sce304

If the system had no water pump then yes, convection would be the means by which the system operated as the heat differentials setup convection currents (some vintage cars were like this and had no water pump!). Reality is that the liquid is force pumped and hence no chance for the convection currents to be be setup hence its actualy conduction cooled.

Pressurised systems are important to understand, hopefuly you have a grasp on the fact that the boiling point of a liquid is dependent on pressure and hence a pressurised coolant system results in the boiling point of water rising above the 100 degC level.

Similarly if you lower the pressure water will boil at room temperature (this is one of the reasons why you vac down air con systems as it boils off any moisture)

[2woody]

the proper term is "pump-assisted thermo-siphon".

most cooling systems work at least partly convectionally - i.e. the coolant enters the bottom of the engine and flows upwards and enters the radiator at the top, cooling as it falls. This generally makes bugger all difference when running, but can be quite important to prevent "afterboil", when the coolant circulates on its own without the engine running.

some engines, however, are "reverse-flow", where the coolant enters the heads first.

[Webby the Bear]

thanks for the replies chaps and mark ill check that link when I'm at a computer. What I'm about to say is going to open a can of worms ha ha. But. My tutor said that the water pump Isnt what forces water round the system and that its the pressure created when it heats up. He said the term water 'pump' is actually inaccurate as it doesn't create any pressure.

[Entwood]

thanks for the replies chaps and mark ill check that link when I'm at a computer. What I'm about to say is going to open a can of worms ha ha. But. My tutor said that the water pump Isnt what forces water round the system and that its the pressure created when it heats up. He said the term water 'pump' is actually inaccurate as it doesn't create any pressure.

No pump in the world creates pressure    All pumps create FLOW. Pressure is only resistance to flow.

Maximum pressure is at minimum flow, maximum flow is at minimum pressure ...

Most pumps are rated as xy/galls(litres)/minute ... ie FLOW,
A very few pumps will be rated at a combination of flow/pressure ... xy galls(litres/min @ z psi(g/sq.cm)

An engine waterpump  is NOT rated for pressure but being a pure vane type will produce more flow at higher rpm, and the system is designed NOT to resist that flow by dynamic pressure.

The increase in static pressure by the radiator cap is a totally different aspect..

[Marks DTM Calib]

thanks for the replies chaps and mark ill check that link when I'm at a computer. What I'm about to say is going to open a can of worms ha ha. But. My tutor said that the water pump Isnt what forces water round the system and that its the pressure created when it heats up. He said the term water 'pump' is actually inaccurate as it doesn't create any pressure.

Lol, hes very wrong.

They do say those that can do and those that cant teach 

If his statement was totaly true then the water would elave the kettle when it was boiled. As per 2Woody, there is a thermo syphon effect based on heat differentails but, its far from enough to cool the engine and hence the pump. Perhaps you should remove the water pump on his car to prove your point 

And as per Entwoods statement, the pump is not there to create pressure (there will be a measureable pressure differential across the pump) its there to 'move' the coolant effectively.

The real pressure increase in the system is due to the heating of the coolant.

[2woody]

Have just fixed a Discovery, which was running as a thermo-siphon only - the coolant pump driveshaft had broken.

The thermo-siphon was good enough to cool the engine at idle and up to about 10mph with very little load, so powerful enough for some running I guess.

[martin42]

water pump is just the same as central heating pump it pushes water around,doesnt create pressure,pressure comes because its basically a sealed system.

[Webby the Bear]

Afternoon fellas, sadly no real update for a while. I've had exam mocks and practical assessments on what i've learned so far so sadly no new awesome info from webby the car bear

i do have some pics to upload though from our assessments so ill upload those tonight.

i do have an interesting topic though and thats oil changes.

i know this is going to open flood gates but hell, whats the point in me blogging if i dont spark debate lol

we had a test on lubricantion system (already covered in this blog) and i mentioned to my tutor that i change my oil every 3k miles. he couldnt believe it and said that was flat out too often. i said the haynes says 5000 but ''from what ive read'' the recommended is 3000.

we then looked on autodata and it said every 10000 miles.


SO. What do you guys reckon? Anybody agree with the 10k? or we all happy that its 3k.
if i was to comment i know for a fact that my engine seems happier doing it every 3k. there seems to be a noticeable smoothness after a change. however, the cost is obviously a lot.

so what do we think?

[Webby the Bear]

oh and one more quickie about oil....

when you're down to '0' miles on the range and bang on empty, did i read somewhere that there are actually still 3 gallons in the tank?

obviously important to know from an mpg working out point of view

[Kevin Wood]

Autodata simply shows the manufacturer's recommendation, which the trade will go by, of course, otherwise customers will complain that they are carrying out unnecessary work.

This recommendation is a compromise between a long-lived engine and a cheap car to run that will be attractive to fleet managers and customers who know no better. After all, the manufacturer doesn't care what happens to the car after the warranty has expired, and the cynic in me would say that they believe that the sooner it's worn out the sooner you'll be queuing up to buy a new one.

The fact is that you can't change oil "flat out too often".

Another thing to consider is that even the manufacturer specifies a shorter interval for "extreme conditions". I would say anything other than a rep blasting up and down a motorway 5 days a week does constitute "extreme conditions". Urban driving and cold starts do it no favours.

How often you decide to change it depends on your usage pattern, attitude to the costs and time involved and personal preference, but nothing but a top-of-the-line synthetic oil will be in good condition after 10,000 miles of typical driving, IMHO, so you're doing the right thing in my book.

Consider also that later petrol Omegas specified an interval of 20,000 miles. (Conditional on the use of a higher spec of oil, admittedly)