cooling system question
Discussion
Hopefully someone can tell me if this is normal behavior for a cooling system.
I've just rebuilt the engine on my 1992 1.6 Eunos. I had the head skimmed and pressure tested, fitted all new gaskets, new waterpump, cambelt etc... The car has now done about 350kms, with no issues. I've been checking the coolant level, oil etc.. before and after every journey, and it was all constant. So far I've just used it with the roof down, so the heater has been on hot all the time.
Today I drove home with the heater off for the first time, and when checking after stopping the level in the expansion tank has risen by about 1 inch. I checked the top hose and it was not pressurized. I took off the rad cap after about 10 mins and there was no pressure release, but the water level has dropped in the rad by about 1 inch (so under the level of the pipe to the expansion tank, just on top of the cooling fins). I can see no signs that the expansion tank has overflowed.
I took the car out (engine still hot) and left it running on the roadside for about 20 minutes. The fan cut in and out every 4 minutes or so, for about 30 secs, temp remained constant, no change in the expansion tank level.
There is no mayo on the dipstick or under the filler cap, and no smell of coolant when hot or cold.
So my question is - is it normal for it to pump some coolant into the expansion tank and then not draw it back as it cools down? Would having the heater on or off make a difference to this behavior? The expansion tank level is now well above the max mark, but the top of the rad has about an inch of air in it. What should I do next?
thanks
James
I've just rebuilt the engine on my 1992 1.6 Eunos. I had the head skimmed and pressure tested, fitted all new gaskets, new waterpump, cambelt etc... The car has now done about 350kms, with no issues. I've been checking the coolant level, oil etc.. before and after every journey, and it was all constant. So far I've just used it with the roof down, so the heater has been on hot all the time.
Today I drove home with the heater off for the first time, and when checking after stopping the level in the expansion tank has risen by about 1 inch. I checked the top hose and it was not pressurized. I took off the rad cap after about 10 mins and there was no pressure release, but the water level has dropped in the rad by about 1 inch (so under the level of the pipe to the expansion tank, just on top of the cooling fins). I can see no signs that the expansion tank has overflowed.
I took the car out (engine still hot) and left it running on the roadside for about 20 minutes. The fan cut in and out every 4 minutes or so, for about 30 secs, temp remained constant, no change in the expansion tank level.
There is no mayo on the dipstick or under the filler cap, and no smell of coolant when hot or cold.
So my question is - is it normal for it to pump some coolant into the expansion tank and then not draw it back as it cools down? Would having the heater on or off make a difference to this behavior? The expansion tank level is now well above the max mark, but the top of the rad has about an inch of air in it. What should I do next?
thanks
James
Edited by anonymous-user on Monday 23 July 19:50
I would fit a new rad cap before doing anything else.
If you have just an expansion tank, ie it is open to atmosphere, then yes the expanding coolant should pass by the spring loaded part of the cap and into the tank. On cooling the coolant should be drawn back into the rad this time passing through the little valve in the end of the cap. The rad should remain full at all times.
Steve
If you have just an expansion tank, ie it is open to atmosphere, then yes the expanding coolant should pass by the spring loaded part of the cap and into the tank. On cooling the coolant should be drawn back into the rad this time passing through the little valve in the end of the cap. The rad should remain full at all times.
Steve
Thanks, yes I had already fitted a new rad cap when I rebuilt it, along with a new thermostat etc..
The expansion tank is open to the atmosphere. I checked it this morning and the level has dropped back down a bit, but its still higher than it was for the past week. The level in the rad has increased a bit also so some fluid has been drawn back through, although it seems to have settled at a different level to the way it has been.
The expansion tank is open to the atmosphere. I checked it this morning and the level has dropped back down a bit, but its still higher than it was for the past week. The level in the rad has increased a bit also so some fluid has been drawn back through, although it seems to have settled at a different level to the way it has been.
Edited by anonymous-user on Tuesday 24th July 10:00
More fun this morning - after about 5 miles the temp gauge was at normal but then suddenly went to about 3/4 towards hot, so I stopped and checked under the bonnet. The rad top hose was still cold, but as I had my hand on it the pipe got hot, presumably as the thermostat opened. I restarted the car and the temp came straight back down to normal.
The thermostat was brand new 2 weeks ago, but there is obviously some problem there - so could a faulty or sticking thermostat have also caused my initial problem where more fluid got pushed into the expansion tank and left the rad top empty?
The thermostat was brand new 2 weeks ago, but there is obviously some problem there - so could a faulty or sticking thermostat have also caused my initial problem where more fluid got pushed into the expansion tank and left the rad top empty?
I'm gonna stick my neck out a little here & say that I don't think you had a problem in the first place. Air moving around after the rebuild & refill of coolant would be my guess. The expansion tank will find it's own level but if you keep taking the caps off every ten minutes your upsetting the system while it's settling in, if that makes sense.
If it's not overheating leave it for a few days to settle without removing the caps & see what happens. Remember that there's not a big difference in degrees temperature between 1/2 & 3/4 on the gauge, but if you think the thermostat is opening at too high a temperature you can always change it for a cooler opening one.
If it's not overheating leave it for a few days to settle without removing the caps & see what happens. Remember that there's not a big difference in degrees temperature between 1/2 & 3/4 on the gauge, but if you think the thermostat is opening at too high a temperature you can always change it for a cooler opening one.
Thanks for the advice, I hope you're right about the rebuild and initial problem, not really from a car health point of view but just because this was my first cylinder head rebuild and I want to have done it right.
I think the thermostat is opening at the correct temperature when it works, as it has been generally fine since the rebuild and held normal temperature even when idling for 20+ minutes. Today it seemed like it just opened really late.
I think the thermostat is opening at the correct temperature when it works, as it has been generally fine since the rebuild and held normal temperature even when idling for 20+ minutes. Today it seemed like it just opened really late.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff