Draining Coolant? Peugeot 406

[derbyshirewhaley]

Hi all, I have been using my Peugeot 406 (2.0 HDi 90) for four years now and she's taken me everywhere. We have a family holiday booked at the end of the month and I've no doubt she'll do it on great fuel economy, but I'd like to tackle a leaking coolant problem.

I initially took the car into the garage last year (as I simply couldn't find the time to get the car on ramps and look around). I noticed a pool of water under the car and the 'low coolant' warning light. It turned out there was a corroded metal pipe at the back of the expansion tank. This was replaced along with the thermostat housing. About a month later the 'low coolant' light came on again and I could see the tank was bone dry (well, the daft 'channel' thing you can see under the cap).

I want to get this sorted before an 800 mile drive. Until now I have simply been topping the car up every 2 weeks with about 500ml of 50:50 coolant/water. That's driving 150 miles a week. I won't be able to realistically do this on a long drive.

I've got some time Friday evening after work, so will drive up onto my ramps and have a look for a leak. Should I find a pipe I can replace, does anybody know how to drain the system on these cars? I can't see anything obvious on the bottom of the radiator -- everything looks plastic and nothing seems like it should be twisted or turned to release. Can post a picture if it's easier!

[CitroJim]

The usual and easiest way to drain is to disconnect the bottom hose at the radiator after removing the expansion tank cap.

As for the leak, a surprising amount of coolant can be lost without any leaks - in the form of drips or puddles - being obvious.

Coolant can escape from very small holes as steam and leave no real trace by leaving the surface wet.

Looks very carefully all over the cooling system for any white, crumbly deposits and/or stains. These will be left by leaks and favourite places are on the ends of hose spigots, the bottom of the radiator, which often corrodes and disintegrates - look for lost fins - and the water pump...

Check the expansion tank cap is good as a weak spring or damaged rubber sealing ring will allow a lot of coolant to be lost through the expansion tank overflow.

The heater matrix can be a cause - often it will give itself away by infusing the cabin with a curry-like smell when the heater is initially set to hot...

When refilling, carefully bleed the cooling system. It's normal for the level to keep falling for a few days after a reflll and repeated bleeds but eventually it'll settle...

These engine should use no coolant at all...

If all the above draws a blank, look for bubbles in the expansion tank that may signify a failing head gasket.

[GiveMeABreak]

The procedure is here in the member's resources section and is identical to the C5 X7, just ignore the pipes diagram at the top, but the procedure including the degassing process (crucial) is the same. Just follow that degassing part for NON Euro 6 vehicles.

viewtopic.php?t=64036

[derbyshirewhaley]

Thanks, both -- that's really helpful. I have a Haynes manual of course but I've found it a bit generic and rubbish. Nothing like a workshop manual I'd use on the Singer. I've printed that guide for the C5 so I will follow it.

As it happens, I actually think I've found the source of the leak...!

I've never been able to find it once parked up, presumably because it's been evaporating. I've had a good look around this evening and when doing so, rested my hand on top of the thermostat housing. After removing my hand I noticed coolant seeping out from the mating surface of the housing. I attempted to tighten the 10mm bolts up but they are on tight and I don't want to crack it. The housing is actually new (fitted by a garage last year when they changed a broken metal coolant pipe) so I will remove it and see if I can create a new gasket with gasket paper or some high temperature gasket sealant.

I've attached a picture of the bottom of the radiator just so you can see the set up. Not sure what clip I'd need for a pipe going into the plastic opening.

EDIT -- seems I need part number 133995 for the metal clip to hold the coolant inlet pipe in.

[GiveMeABreak]

I'll have a check for you - but at present Stellantis are having major issues with their portal, so parts service is offline at present. I'll bookmark this topic and return with the part number for clip once service is restored.

[derbyshirewhaley]

I'll have a check for you - but at present Stellantis are having major issues with their portal, so parts service is offline at present. I'll bookmark this topic and return with the part number for clip once service is restored.

Thank you -- whenever you get the chance. I appreciate the time taken to look. It may be that the clip I have is re-usable, but I'd rather just replace with new.

[wheeler]

The part no of the clip on the bottom pipe is indeed 133995 & is £3.49 inc VAT
There is a thermostat seal in the housing (part no 134048 £7.50 inc VAT) might be worth replacing it at the same time.

[derbyshirewhaley]

The part no of the clip on the bottom pipe is indeed 133995 & is £3.49 inc VAT
There is a thermostat seal in the housing (part no 134048 £7.50 inc VAT) might be worth replacing it at the same time.

Thanks a lot for that, I’ve just ordered the parts. Hopefully get them for the weekend.

[CitroJim]

Excellent! Looks like a result

[derbyshirewhaley]

Excellent! Looks like a result

Yes, had another look this morning and there's an obvious trail of coolant staining which runs all the way down to the sump. I think a lot of this was being burnt off/evaporated during a drive so I wasn't able to find it very easily.

Thanks again all for the help, I'll post results on here once done.

[Hell Razor5543]

A trick that might help is to draw horizontal lines of chalk around the engine. Then, if there is a leak, the chalk below the leak should be washed away, helping you to track the leak down.

[derbyshirewhaley]

I'll remember that one for the future!

[PaulC5]

If just removing the thermostat you only need to drain a relatively small amount of coolant. If there is a small diameter pipe from the thermostat housing that goes to the expansion tank, simply unclip it at the tank end and then lower this end into a bottle. If the end is held just below the thermostat level then it will drain that far. Collecting the coolant in a bottle or 2 also makes it easier to pour back in the tank. I have used this method on our C5 and also a neighbour's van but since he is a plumber he sucked the coolant out into a wet and dry vac.

Any refilling procedures will need to be followed to get out any air. On our C5 it requires a special tool to give a coolant level higher than the expansion tank but I made one out of some basin waste pipe about 1 foot long with its seal and cutting a hole in an expansion tank cap to go around the pipe and tighten it in the tank.

[CitroJim]

Any refilling procedures will need to be followed to get out any air. On our C5 it requires a special tool to give a coolant level higher than the expansion tank but I made one out of some basin waste pipe about 1 foot long with its seal and cutting a hole in an expansion tank cap to go around the pipe and tighten it in the tank.

Absolutely Paul, an essential tool for the job and thanks for advising of its necessity I like your method of making one

Failing that, and as a 'quick and dirty' solution, an old 2 litre fizzy pop bottle and a big lump of Plasticine works pretty well

[derbyshirewhaley]

If just removing the thermostat you only need to drain a relatively small amount of coolant. If there is a small diameter pipe from the thermostat housing that goes to the expansion tank, simply unclip it at the tank end and then lower this end into a bottle. If the end is held just below the thermostat level then it will drain that far. Collecting the coolant in a bottle or 2 also makes it easier to pour back in the tank. I have used this method on our C5 and also a neighbour's van but since he is a plumber he sucked the coolant out into a wet and dry vac.

Yes there is the pipe you mention, it’s just visible at the edge of the photo I posted earlier.

That’s a very good suggestion so I will follow that method! I’ll judge the state of the fluid that comes out and may end up replacing it all anyway.

In terms of the refilling method, I’ve always just jacked the car up so the expansion tank is higher than anything else and when filled, ran the engine up to temp with the bleed screws open. When fluid comes out I’ve closed them. Hope this isn’t some sacrilegious method!