coolant probelm

[DennisTheMenace]

I changed the engine on my 5 at the weekend for a 55,000k lump out of a rolled car , bought it untested but then i didnt pay a lot for it .
Got it all in and running fine sounds nice and smooth and drives very well , then i noticed the coolant in the reservoir was going up and not getting pulled back into the engine , BTW there is no white smoke when driving and the rad fan kicks in ok, ive been flushing it through and refilled and its now bubbling small bubbles out of the rad cap and pushing the water out , is it HGF or something simple ??

Plase say something simple ....

little vid of the problem

http://smg.photobucket.com/albums/v402/DennyRobert...

Edited by DennisTheMenace on Thursday 2nd October 22:30

[MX-5 Lazza]

Without the cap on some water will overflow, that's normal. If the cap is working correctly it should keep pressure in the system. With the cap on does it flow into the expansion tank constantly or does it stay pretty much level?

Did you change the thermostat?

[DennisTheMenace]

i didnt , but there is a constant stream of tiny bubbles and that frothing do you thing it could be the stat then?
when the cap is on there is a constant stream of bubbles in the reservoir , if i put my fingers over teh pipes they build pressure , odd thing is there is no sign of coolant in the piston chambers or any steam from the exhaust

i reckon the caps fine , never had any issues with the old engine

[MX-5 Lazza]

There is probably just some air in the system then. Just let it run for a while with the cap off and keep topping it up until you get fewer bubbles. Squeeze the bottom hose a bit while it's running (take care to avoid the fan) to help the bubbles flow. After that, put the cap back on and go for a bit of a drive then check the water level in the expansion tank. If it's low top up in the expansion tank only - don't take the rad-cap off again if you don't have to.

The thermostat is probably fine, it was just a general enquiry. Probably a good idea to replace it when you do the next service though.

[franv8]

These things are a git to diagnose (I'll put that down to the blame for why it took me three months to suss that there was a crack in my cylinder head...)

Lets pretend for a moment it's the head gasket. There is only a max of about 1 bar of pressure in cooling system, so that's what will drive coolant into the piston chamber. THat was enough to put a very slow dribble into my No 3 cylinder.



On the combustion side, it's got at least 8 bar from compression pressure (+ loads more from fuel burning) - so it'll likely force gas into the cooling system.

THis is partly scare mongering though, it can be tested with a kit many mechanics will have (or you can get one yourself) - that basically tests a sample of coolant for exhaust gases.

Can I ask, have you bled your system when you filled it up? I do this just by putting the heater on hot, running the engine up with the rad cap off, at fast idle, from cold. It will randomnly spit coolant out, you have to accept a bit of loss and keep topping the rad up, it will suddenly drop half an inch and stay there, fill it back up and then put the cap off. Take out for a blat and test! (independently ensure that the overflow bottle is filled to its max line, again car may lose a little once everything's heated up then it should stop doing this).

If after doing this there is still an issue, it'll need further investigation. I did have a problem with a failing water pump, the trouble is again the leak was slight, only evidenced by the staining on the block once the cambelt cover was completely removed, it was allowing air back into the system though when the car was stopped and cooling down, caused all sorts of cooling system weirdness before correct diagnosis.

[DennisTheMenace]

cheers for teh replies chaps , ive fixed the link to the vid so now you can see the problem , im really hoping its something stupid , it does do it pretty much from cold , so im guessing its not a cracked head . its a shame really compared to my old engine its transformed the car , nice and smooth noe to drive and a bit more grunt

[franv8]

The old swarf caught in the bypass pipe in the thermostat housing - is that something that happens to 1.8's too?

[MX-5 Lazza]

franv8 said:

The old swarf caught in the bypass pipe in the thermostat housing - is that something that happens to 1.8's too?

It can but I'd expect that to cause cold running problems rather than coolant surge.

[DennisTheMenace]

sniff test done no co2 in the coolant even with no pressure in the system its bubbling in the expansion bottle , so trying a cap .

[MX-5 Lazza]

DennisTheMenace said:

sniff test done no co2 in the coolant even with no pressure in the system its bubbling in the expansion bottle , so trying a cap .

Only use a genuine Mazda rad cap. The aftermarket parts aren't anywhere near as good. Same goes for Thermostat.

[DennisTheMenace]

trying a cheap one now , and will order a proper jobbies when they become available , or i will try a mazda dealer when im traveling past one .

[DennisTheMenace]

well didnt work and wasnt expecting it to , off with the head i reckon

[zac510]

Are you sure you have bled it all correctly?

[Barry Ashcroft]

Sell it and buy a TVR

[MX-5 Lazza]

What symptoms do you have now? With the cap on I mean.

[DennisTheMenace]

swap ya barry

its pushing coolant out into the expansion bottle then over flowing its always trying to push the coolant out , took the stat out and it still does it , gasket or cracked head (which i doubt) can be the only thing .

[MX-5 Lazza]

It sounds like there is a blockage to me.
Have you tried back-flushing the engine with a hose-pipe to make sure water flows through the block?

[zac510]

It will push the coolant out if the cap is not holding pressure. As the coolant heats up it expands etc etc

[DennisTheMenace]

yep , flushed it in both directions

[DennisTheMenace]

took the stat out and blasted water into the front , and left it to drain out of the radiator drain hole untill it was clear , flushed the heater matrix out when i have the engine out as well.