Big Mark Posted July 23, 2014 Share Posted July 23, 2014 (edited) The last few days I've noticed a hiss coming from the car after I park up. Had a look and it's the coolant expansion tank letting off steam to the point that the level was really low so i've just topped it up. Temp gauge in the car is in it's usual place, not high. Anyone know what's going on? Edited July 23, 2014 by Big Mark (see edit history) Quote Link to comment Share on other sites More sharing options...
The-Plethora Posted July 23, 2014 Share Posted July 23, 2014 How old is your radiator cap? Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted July 23, 2014 Share Posted July 23, 2014 It could be a faulty radiator cap . . . but what's the level in the radiator like? If that's low, you probably just have a leak in one of the hoses (even a pin-prick hole in one of the tiny hoses will be enough) And you can often lose some coolant without it affecting the engine's temperature gauge. If coolant level is normal, then it could be a blown head gasket pressurising the cooling system. (that causes the effect you're talking about) Is your car a Turbo? And producing more power than stock? Quote Link to comment Share on other sites More sharing options...
Big Mark Posted July 23, 2014 Author Share Posted July 23, 2014 My car is BPU The steam is definitely coming from the plastic cap on the expansion tank. If I press hard on the cap or squeeze the pipe from that goes to the expansion tank the steam stops. Could it just be that I need a new cap on the expansion tank? Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted July 23, 2014 Share Posted July 23, 2014 (edited) No the steam is coming from the pipe under your Radiator cap INTO your expansion tank - that is the problem The radiator cap is designed to open if the pressure in the system increases to allow excess coolant to flow into the expansion tank (and vice versa) But you normally should have hot liquid coming into it - if you have STEAM coming into the expansion tank, that implies something is wrong - as I suggested in my previous post As I asked you before, what is the level of coolant in the radiator like - is it right to the top? (obviously only ever open the cap when the engine has cooled down a lot) If it's NOT, then I suggest you either have a leak in the cooling system somewhere, or a blowing head gasket. You could also make sure the rubber on the lower part of the radiator cap isn't split. (Otherwise, in my experience, if the the radiator cap becomes faulty, they normally don't open when they should, rather than open too soon) Edited July 23, 2014 by Roger NE (see edit history) Quote Link to comment Share on other sites More sharing options...
Big Mark Posted July 23, 2014 Author Share Posted July 23, 2014 I see. I'll pop out at lunch time and have a look. Quote Link to comment Share on other sites More sharing options...
Big Mark Posted July 23, 2014 Author Share Posted July 23, 2014 Just had a and radiator was low so put almost 1.5 litre in it plus I put almost a litre in the expansion tank. Ran it up to temp and couldn't see anything untoward, but I did notice that the rubber on the end of the radiator cap came off when I took the cap off. I'll get a new one this week. Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted July 23, 2014 Share Posted July 23, 2014 Well definitely replace the radiator cap . . . but that may not be the cause of the problem. Once you've replaced it, I would be checking the level of coolant in the radiator every couple of days - if it is still going down at all, then you have a leak. This could be due to the radiator, or possibly the HG . . . but more likely one of the hoses. All the hoses should really replaced every 10 years, but I bet yours haven't ever been! If a leak isn't obvious, it's probably one of the really small hoses - I spent months trying to find a leak, which only became apparent when I replaced all my hoses, and when it was off I found one of the small ones had a very tiny split. Quote Link to comment Share on other sites More sharing options...
Big Mark Posted July 23, 2014 Author Share Posted July 23, 2014 Am I right in thinking that the radiator should have a spring in it and be able to move under pressure? Mine doesn't at all. Pretty sure it's dead and hence why it's releasing the steam. Hose to expansion tank and top rad hose were replaced with silicon ones last year with bottom one in a box at home to be fitted. Quote Link to comment Share on other sites More sharing options...
brom86 Posted July 23, 2014 Share Posted July 23, 2014 Am having the same issue. Only seems to happen more when it's really warm day. Mine is an na though but exact same symptoms. A changed rad cap and thermostat and still does it. Got a second hand radiator to change over. Also had a sniff test done and there was no exhaust gases in the collant so wasn't head gasket. Very rare for hg to go. Hope we can both get this sorted haha Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted July 23, 2014 Share Posted July 23, 2014 (edited) If you're losing coolant, the leak COULD be from the radiator or the Water Pump . . . but far more likely to be from one of the hoses. As I say, it's not just the main big hoses to and from the radiator - it's the medium size and small hoses (to the heater and other parts of the engine) that are more prone to tiny holes or splits that you can't even see. (and silicone hoses seem to split more than proper rubber ones do) You'd think that you'd see signs of a leak (dripping coolant or steam) from a split hose . . . but I never could when I had this problem about 5 years ago. (that's why it tool me months to find the culprit) It was only when I took the offending tiny hose off that I saw the split. Edited July 23, 2014 by Roger NE (see edit history) Quote Link to comment Share on other sites More sharing options...
stevie_b Posted July 23, 2014 Share Posted July 23, 2014 If there's coolant loss (which is the case for the OP at least), you could take it to a garage and ask them to do a pressure test on the system. That should highlight any small, hard-to-find leaks in the system. Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted July 23, 2014 Share Posted July 23, 2014 Yes but if you can't see where exactly it's leaking from due to the normal pressure the system develops when it's hot, I doubt if a Pressure Test will help reveal it either ! Either way, you might as well check it yourself first. Fill the radiator right up, put the cap on, run the engine up to temperature, then look for leaks. Using a bit of paper kitchen towel is a good tip - wipe it round the length of ALL the small hoses - if there's any sign of dampness on the paper towel, that's where your leak is. Quote Link to comment Share on other sites More sharing options...
Big Mark Posted July 23, 2014 Author Share Posted July 23, 2014 New radiator cap now on, old one was f**ked, rubber on base wasn't attached and the spring had failed. Checked a few places but going to double check pipes to the heater as I had these off earlier in the year to flush the matrix so when it' all cooled down will check tightness. And then keep a eye on things. Thanks for the advice. Quote Link to comment Share on other sites More sharing options...
Guest Roger NE Posted July 23, 2014 Share Posted July 23, 2014 Well the main thing to check is your coolant level - the radiator should be full to the brim when cold. If it IS, then everything is OK . . . if it ISN'T, you have a leak somewhere ! This should be a normal weekly check anyway . . . and one I always do, along with engine dipstick, clutch and brake fluid levels, and tyre pressures. (checking the whole lot takes about 60 seconds . . . and avoids any problems!) Quote Link to comment Share on other sites More sharing options...
Big Mark Posted August 22, 2014 Author Share Posted August 22, 2014 More steam again tonight. It was definitely coming from the battery side of the enginer bay and from low down but as far as I know there are no pipes down the bottom of that side of the radiator. But is the drain plug that side? Quote Link to comment Share on other sites More sharing options...
brom86 Posted August 23, 2014 Share Posted August 23, 2014 I changed my rad over and I have had no issues since. Thank god!! There was a small chip just inside the rad at the lip where the rad cap seals too inside, I think it was that. System wasn't pressurised because of this causing the coolant to get real warm causing steam. Worth a try and my second hand rad from the forum cost 38 delivered. Worth ruling out things cheap before HG changes ect Quote Link to comment Share on other sites More sharing options...
Big Mark Posted August 23, 2014 Author Share Posted August 23, 2014 Yeah I'm pretty sure it's coming from the bottom of the radiator somewhere. If I was lucky I'd say it's just the drain maybe, but knowing my luck it's the rad itself. Hoping tomorrow it will get me from Rugby, to The Falcon, to The Heritage museum, back to The Falcon and then home with maybe just a top up of two and I'll have a proper investigation on bank holiday monday. Quote Link to comment Share on other sites More sharing options...
Big Mark Posted August 24, 2014 Author Share Posted August 24, 2014 Woke up early so had the car off the ground, undertray partially off and one of the fixing screws was wet below the area of the drain plug. Got a little turn on the plug so fingers crossed it was that, if not then I'll get myself a new auto transmission radiator. Time to clean up and head off for the anniversary meet. Let's hope its a good day and I'll see those of you that are going shortly! Quote Link to comment Share on other sites More sharing options...
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