Peugeot 206 - Bleeding air out of the system (car is overheating

Honest John Back Room » Technical matters
View Threaded
Fri 15 Mar 2019 17:57
Peugeot 206 - Bleeding air out of the system (car is overheating - OceanMan

Hello,

My car has been overheating a lot recently. Sometimes on the motorway, sometimes in slower traffic. I refilled the coolant a few days ago, and I've been told this could have left air in the system which can cause overheating. A mechanic gave me advice on what to do, open the bleed screws and let air and water drain, but I've forgotten specifically what he said.

Where can I find the bleed screws on a 2005 Peugeot 206(1.4 L Petrol) and what should I expect to see when I open them?

I've googled this, but all of the methods of getting air out of the system seem to vary so much.

Thanks in advance for any help

Reply | Report as offensive | Link
Sat 16 Mar 2019 09:22
Peugeot 206 - Bleeding air out of the system (car is overheating - John F

If you've had to refill the coolant, the original coolant must have gone somewhere. If there is no sign of a leak from a hose, rad or water pump, the most likely explanation in a car this age is a failed cylinder head gasket. Every turn of the engine sucks in a tiny drop and blows it out of the exhaust. It's the unwritten rule of motoring - when you have to start topping up the coolant, sell the car. And if you buy an old second hand car, watch the coolant level like a hawk for the first few hundred miles. And don't buy it at all if it, or the plastic tank, is a dirty brown colour. The (original) coolant in our eighteen year old 136,000 mile Focus is crystal clear magenta in a white tank.

Reply | Report as offensive | Link
Sat 16 Mar 2019 15:42
Peugeot 206 - Bleeding air out of the system (car is overheating - OceanMan

Do you think it would be a good idea to do a complete coolant flush then? I got this car v cheap recently and I've already spent a lot of mine trying to improve it so I'd rather avoid selling it, as my budget would only stretch to about £1000 do obviously any car at that price is a risk anyway.

Thanks a lot for the response by the way

Reply | Report as offensive | Link
Sat 16 Mar 2019 15:51
Peugeot 206 - Bleeding air out of the system (car is overheating - Big Musky

To be sure regarding your potential head gasket failure you can do a compression test and compare the results with the manufacturers specifications. Or you can get a head gasket testing kit which is inexpensive. It screws onto the radiator or most likely the expansion bottle. You put the testing solution in the kit into the fitting on the expansion bottle, start the engine and if there are combustion gasses getting into the coolant (ie head gasket gone) the solution will change colour. Just a thought, which may help.

Reply | Report as offensive | Link
Sun 17 Mar 2019 02:17
Peugeot 206 - Bleeding air out of the system (car is overheating - edlithgow

Do you think it would be a good idea to do a complete coolant flush then?

Depending on what coolant you are using (which is too complicated to get into, and pointless here in Taiwan since its almost impossible to find out what's in the stuff on sale) a flush and change might be indicated every 2 years.

Its probably unlikely to do anything to address your immediate problem.

The question, though, seems to imply that earlier you were just "topping up".

This in turn implies coolant loss, which I'm afraid tends to indicate a head gasket problem.

Its possible for an airlock to cause coolant loss (by blowing it out of the reservoir as the air expands, for example) but it seems unlikely you could get an airlock just by topping up.

Reply | Report as offensive | Link
Sat 16 Mar 2019 23:32
Peugeot 206 - Bleeding air out of the system (car is overheating - Andrew-T

I'm not clear whether you had to top up the coolant because of losses, or you decided to change the whole lot and now think you may have an airlock.

If the first, you may have a potentially expensive problem, as John-F says. If the latter, you just need to slightly open the bleed screws while the engine is running to clear the airlock (which will in time clear anyway, but at the risk of overheating). Find a Haynes manual, perhaps in your local library if you don't want to buy one - it will show where the bleed points are.

Reply | Report as offensive | Link
Sun 17 Mar 2019 01:05
Peugeot 206 - Bleeding air out of the system (car is overheating - edlithgow

I had an airlock problem fairly recently which I thought, and was told by everyone and his dog on the internyet, was a blown head gasket, (3-cylinder engines tend to be especially prone to them) but it cleared in time with (touch wood) no apparent damage.

I'd say the risk with letting an airlock clear itself might be that it causes local overheating which then blows the head gasket, self-fulfilling-prophecy-of-doom stylee.

Some cars are allegedly especially prone to airlocks (VAG gets mentioned) and require vacuum filling, for which gadgets are apparently available on the US market, dunno about the UK,

If there's a next time I'll probably try a big sink-unblocking syringe to "burp" the system, or maybe a venturi pump. If you've got bleed screws (none on my car) you may not need to do this,

IF it turns out to be a head gasket problem there are stop-leak tablets (Barrs Stop-Leak IIRC) based on ginger root fibres . Never used them but they allegedly sometimes work, at least for a while, and aren't very expensive.

Compression test, leak-down-test, cooling system pressure test, and exhaust-gas-in-coolant test may give diagnostic clues, the exhaust gas test probably being the most sensitive.

Edited by edlithgow on 17/03/2019 at 01:11

Reply | Report as offensive | Link
Sun 17 Mar 2019 17:06
Peugeot 206 - Bleeding air out of the system (car is overheating - OceanMan

Honestly o think I topped up the coolant in error, because I thought there was none left. I looked at the "overfill" tank and say that it was empty so poured more in. Though ive siincelearned that coolant doesn't always show in this tank, so I may have added too much.

Thanks for the advice re Haynes. Obviously a simple thing to do, ill try to buy an ebook version if they're a thing

Reply | Report as offensive | Link
Sun 17 Mar 2019 23:24
Peugeot 206 - Bleeding air out of the system (car is overheating - Andrew-T

Honestly o think I topped up the coolant in error, because I thought there was none left. I looked at the "overfill" tank and say that it was empty so poured more in. Though ive siince learned that coolant doesn't always show in this tank, so I may have added too much.

If all you have done is add more coolant (I hope it was the right type/colour?) you should be OK, but you need to find out where the level should be (check with engine cold). In perfect conditions the level should not change, but if there is a slight loss of pressure somewhere it could drop very slowly. Adding 'too much' should not matter as long as there is plenty of ullage for expansion as the coolant heats up.

Reply | Report as offensive | Link
Sun 17 Mar 2019 07:35
Peugeot 206 - Bleeding air out of the system (car is overheating - S40 Man

Does your heater matrix work? An old trick is to blow hot air out of the air vents. This is heat that comes from the engine cooling system (indirectly). Useful to know if your car gets hit on the motorway again.

If you can't get hot air that's a good sign something is amiss.

Reply | Report as offensive | Link
Sat 23 Mar 2019 21:26
Peugeot 206 - Bleeding air out of the system (car is overheating - OceanMan

Just an update. It seems it was the thermostat that was the problem. I got that changed last week and it's been fine since. Thanks for all the responses.

Reply | Report as offensive | Link
Sat 23 Mar 2019 23:11
Peugeot 206 - Bleeding air out of the system (car is overheating - Andrew-T

Thanks for the update, OM, and good to know it was a cheap fix (which you could have DiY probably). At least no headaches about head gaskets ....

Reply | Report as offensive | Link
Sun 24 Mar 2019 16:51
Peugeot 206 - Bleeding air out of the system (car is overheating - OceanMan

I probably could have done it myself, but without knowing what the problem was I was facing a list of half a dozen potential causes. I could have gone all the way through that list before getting to the thermostat, which might have cost me more in the long run

Reply | Report as offensive | Link
Sat 6 Apr 2019 10:47
Peugeot 206 - Bleeding air out of the system (car is overheating - Bromptonaut

Coolant level varying can be a sign of a blown head gasket. Combustion gas in coolant channels round head and block displaces coolant making it look artificially high in, or even leak out from, expansion bottle. Gas then works its way back to bottle and coolant level drops dramatically.

My Peugeot 104 owned from 82-86 played this trick regularly.

Reply | Report as offensive | Link