Expansion Tank

[Guest timswait]

Is there any good reason for fitting an expansion tank? When I built my car I didn't fit one and it ran hot, so I put one in (putting the spur off the top hose into the bottom of the Sierra one, and blocking off the top hole) but it still ran as hot as ever. Now I've fitted the 2 litre there's even less space to squeeze one in, and I can't see the point. I was going to fit the heater matrix as a second radiator just behind the main one.

[Big Jim]

The answer to your question is yes, but it will not cure overheating.

 

As your water gets hot, it will expand, and blow some out of the overflow pipe into the expansion tank, as it cools, it is sucked back into the radiator (providing the cap is a 2 way one, and the pipes are correct) If you don't have a tank, you will find when you check your water, that the level is only just above the tubes in the rad. S oyou do need to fit one.

If you car is overheating, then first check that the thermostat is in the correct way round. (common fault) and working OK. (this was on the board last week. search for it). The next problem is that the fan is not doing it's job, usually because its too far away from the radiator fins (should be less than an inch away) or if it's a 2B, and you've had to tilt the radiator, then put the fan miles away from it, you MUST fit a cowl, so that all the air the fan blows, has to go through the radiator, not around or over / under it. Next, the fan that RH sold with the 2B is a 'Sucker' if you are using it to 'Blow' it will barely be good enough even if you cowl it all in. try a fan from a Citreon BX they blow (like hell!) but you'll need to go through a relay, and at least a 30 amp fuse on the feed line.

It's all down to getting air through the radiator.

You could also go for a two core radiator.

[Guest timswait]

When I used the Sierra one I used the spur off the top hose to go in the bottom of the Sierra tank. I had heard of people putting a pipe on the outlet on the rad cap and running this into a bottle to catch the water. Which is better?

[Guest Takumi]

An expansion tank is not actual needed , although if you want to impliment one you sure can, if you can find the space..hehe

 

The reason you dont totaly need an coolant expansion tank, is that it is a ve+ pressure closed system ( thesse are actually more efficient..) note the radiator cap has a release pressure of 1.3 BAR, this pressure is experienced when coolant temperature has reached way beyond the std 103c temp switch, so as long as you've used the electric fan, and the original temp switch from the sierra radiator ( not originally for a fan switch on.) coolant will be kept at managable temperatures.

Make sure there are no air bullbes in the system when filling.

This will cause traps and over heating problems at the extreme.

 

hope you get it sorted.

tak

[Longboarder]

The main reason to fit an expansion tank is when you heat a gallon of water from 20 to 80 centigrade it expands by about half a pint, very roughly.(40 years since I did physics O level). This 'extra' water has to go somewhere and that can't be just stretching the hoses a little. If you sealed the rad cap something would blow. So an expansion tank allows the 'extra' water to leave the system but return when it cools. I've seen the temp guage drop radicaly on the motorway at 70mph. If the take off to the expansion tank is at the highest point in the system then it will also bleed any trapped air which is a bonus. The tank can be at any height and in the nose cone if space is short.

I would say fit one. (But agree it won't cure overheating)

 

Nigel

[Guest Takumi]

If you go-on to use an expansion tank, it must be higher than the level of coolant in the head/block, because a) system is full from the bottom>up, and will exapnd up and out of the system, if it were eg. the same height as the water pump, it wouldnt work as an expansion tank as it would be ompletely full of coolant.

 

Expansion tanks, when used, have to be higher than the water level in the engine, about level with the cam cover..

 

tak

[Guest daveg]

All

 

I agree completely with what Jim has said, also the expansion tank can be at any height, the only very important thing is that the pipe leading from the top of the radiator to the expansion tank/bottle must be submerged in water indide the tank.

 

Also, the radiator cap must be the right type....the pipe must be after the cap. Otherwise you will need a pressurised expansion tank-complicated and no point.

 

Dave