Boiling expansion tank

[kbj149]

Hi all,

Couple of things, if I've driven the car solidly for half an hour the idle begins to hesitate, it purrs just fine when I fire it up but over time it starts to wheeze a bit when in neutral with the oil pressure gauge bouncing. This coincides with water boiling in the expansion tank, I foolishly opened it the other day and it just sprayed everywhere. There is a small leak on one of the hoses but nothing significant, I wonder if its creating an air lock maybe? If I were to get the hose sorted would it make much difference? The expansion tank doesnt lose any significant water as its a very minor leak. I've noted the hot air blower is not actually that hot, more luke warm, I think this could point to a cooling problem. When I encounter the hesitant idle, the car is also difficult to then start up, I think this all points to over heating perhaps.

Any thoughts? I've had it flushed but I'm sure the coolant isn't supposed to be at boiling point? The fan is also always on, even when started up from cold, is this right?

Apologies for a somewhat newbie question but, well, I am!

Thanks in advance.

Kev.

[Brap_Brap]

kbj149 said:

Hi all,

Couple of things, if I've driven the car solidly for half an hour the idle begins to hesitate, it purrs just fine when I fire it up but over time it starts to wheeze a bit when in neutral with the oil pressure gauge bouncing. This coincides with water boiling in the expansion tank, I foolishly opened it the other day and it just sprayed everywhere. There is a small leak on one of the hoses but nothing significant, I wonder if its creating an air lock maybe? If I were to get the hose sorted would it make much difference? The expansion tank doesnt lose any significant water as its a very minor leak. I've noted the hot air blower is not actually that hot, more luke warm, I think this could point to a cooling problem. When I encounter the hesitant idle, the car is also difficult to then start up, I think this all points to over heating perhaps.

Any thoughts? I've had it flushed but I'm sure the coolant isn't supposed to be at boiling point? The fan is also always on, even when started up from cold, is this right?

Apologies for a somewhat newbie question but, well, I am!

Thanks in advance.

Kev.

Just my layman's thoghts here...

If it's boiling in the tank it's boiling in the rad, (proves themostat is open) so either the rad's junk and can't cool properly or perhaps it's backing up due to a blocked or kinked lower rad hose.

Edited by Brap_Brap on Saturday 11th July 17:33

[Number 7]

You need to tell us what engine you have as the pic in your profile doesn't work. If an RV8, they can be tricky to bleed air from the cooling system - and you say that you had it flushed, so there may still be air in there. Again, if RV8, the fan should only come on when triggered by the otter switch (N/S top of radiator tank) - access can be tricky - may need to remove the headlight pod. As an emergency, if you short the two wires leading to the otter switch together, the fan stays on whilst the ignition is on. Worth checking if someone has done this to overcome a heating problem.

7.

[grahamw48]

I got the pic to expose itself, and looks like a 280.

PLEASE fellow Wedgers ...give us a clue as to what car/engine you have!

Oh, and if you have a (viscous) fan attached to the front of the engine, as on early 280, then it is mechanically driven all the time...like on old-fashioned cars that old people like me are quite used to.

Haven't we just had this discussion, or am I REALLY going senile ?

Edited by grahamw48 on Saturday 11th July 20:11

[jeff m]

Fix the small leak.....

Yes it will make a difference....you will have pressure.

Also if you have a leak the system will not self bleed.
Self bleed means get it hot, fill tank, let it cool....get it hot, fill tank let it cool. (heater switched to hot before you start.)

I would suggest new rad caps too.

Now check for hot air from heater.
If none repost.

[peaktorque]

Higher pressure means = higher boiling point.

If you are loosing pressure (as in leak) then the water will boil.

Fix the leak........

[Wedg1e]

peaktorque said:

Higher pressure means = higher boiling point.

If you are loosing pressure (as in leak) then the water will boil.

Fix the leak........

Hear hear!

Just had a recurrence of the leak on my expansion tank... car now on its second tank that I know of. It split in the same place both times; where the small-bore stub exits near the front left corner of the tank. What happens is that the tanks were blow-moulded around steel inserts; the inserts corrode and swell, causing the polythene tank to split.
You can repair it: what you need is a soldering iron (preferably a variable temperature one) and a selection of carrier bags
Adjust the iron so it's hot enough to melt the plastic but not vapourise it. Then experiment with melting the plastic bags into the tank around the leak. When you have the same type of polythene the two should meld quite nicely. I found a clear bag with no printing worked best: Tesco, Morrisons and some others (all white) would not 'flow'.

That said, some time back I did buy an alloy filler neck with the intention of welding up an aluminium tank... maybe now would be a good time to crack on with it!

[RedRum350i]

Had a problem with coolant filling the overflow tank. As per Jeff M's suggestion got new rad caps which solved the problem - keeps the pressure in and stops the collant boiling over. The new pressure cap (expansion tank one) works fine, but one word of caution, if you need to replace the swan neck cap as well, the general one available comes with just an O-shaped washer, which didn't make a seal for me. It actually needs a full rubber disk, or plenty of silicone sealant!

[TVRleigh_BBWR]

RedRum350i said:

Had a problem with coolant filling the overflow tank. As per Jeff M's suggestion got new rad caps which solved the problem - keeps the pressure in and stops the collant boiling over. The new pressure cap (expansion tank one) works fine, but one word of caution, if you need to replace the swan neck cap as well, the general one available comes with just an O-shaped washer, which didn't make a seal for me. It actually needs a full rubber disk, or plenty of silicone sealant!

Best to get a normal cap, and just cut off the pressure bit, so it's just a cap.

Also last year I got several Ali Expansion tanks made, they was only made to order though.

[Barkychoc]

If you've got a slight leak you'll be bleeding it forever - as the engine cools the leak will work the other way and the cooling system will suck air in as it cools down.

[kbj149]

Thanks all - very much!