Is it safe to......

[nicky.mattsson]

run the engine with a coolant hose off?

I have just replaced the waterpump on my MX5 and want to replace ALL of the coolant. I was thinking of running the engine for a few minutes without one of the coolant hoses attached in order to make sure there is no old coolant in the system before i refill it.

Is this ok or is there an easier/safer way of removing all of the old coolant.

Cheers

Nick

[steve j]

nicky.mattsson said:

run the engine with a coolant hose off?

I have just replaced the waterpump on my MX5 and want to replace ALL of the coolant. I was thinking of running the engine for a few minutes without one of the coolant hoses attached in order to make sure there is no old coolant in the system before i refill it.

Is this ok or is there an easier/safer way of removing all of the old coolant.

Cheers

Nick

Nicky, not really a good idea as the water pump is probably empty, try attaching a hose from your tap and flush out the system, engine not running of course.

[bertelli_1]

If you run it for a few minutes it will overheat, severely. Most radiators have a drain which will get most out. You could refil it with water, run it and then redrain.

[nicky.mattsson]

What about running the engine with a hose off and a garden hose in the top of the rad to keep a constant supply of water so as not to dry it out?

[TheEnd]

nicky.mattsson said:

What about running the engine with a hose off and a garden hose in the top of the rad to keep a constant supply of water so as not to dry it out?

I've seen people do similar. You won't get as much through the hose as the pump will kick out though.
Try just filling it with water, drain again, and you should have next to nothing left of the old stuff anyway.

[Mr2Mike]

Running it for maybe 20 or 30 seconds with no coolant is ok, but certainly not "minutes".

[fatjon]

When the coolant gets below the level of the pump it will stop pumping anyway so you will still have more water left in the engine and rad than if you just took off the bottom radiator hose.

[GLLHG]

Why not keep it simple ( and err on the side of caution)- drop the hoses, take off all rad and expansion tank caps and flush it through with the engine off and garden hose on a good flow rate. Don't forget, if you try to use too much pressure then there is always the possiblity of damaging the rad core
It goes without saying, when you refit and refill, check for any air locks

[Ricky_M]

Just re-fill and drain a few times with fresh water, that should dilute it enough so no old coolant is left in there.