406oc.co.uk

Hi newbie here!

I recently bought a 406 hdi 90 on an 02 with a problem. It seems the coolant is pressurising under load (a 15-30 min drive) and then blowing out of the top of the coolant reservoir cap and level sensor. Now obvious to me is head gasket so i put a sniffer on the bottle and it did not change colour. There is no water in the oil nor oil in the water, it does NOT overheat ever. However even when the car has cooled down say over night if you release the coolant cap there is a pressure release noise. Also the hoses do swell under the pressure. The car has 105,000 miles on it.

Another thing, this maybe unrelated, but the oil dipstick can get pushed up clear of the engine too, could this be a blocked breather?

Just se if anyone has ideas or seen this before?

On another note, can you simply bolt on the intercooler from a 110 if you have the pipes from the turbo and to the manifold?

Please help im a rather puzzled mechanic!!

All modern and less modern cars have a pressure realief valve in the cap.

There is supposed to be some pressure there (usually somthing like 1 to 1.4 bar pressure)

but the cap has a valve to let air in when the car cools down to stop a vacuum forming, and one to let air/water out when it goes above pressure too.

YOu sure that's not air going in when you release the cap in the morning? You over-filling it?

lazarus79 wrote:and level sensor

is this missing/leaking or do you mean the overflow?

Replace the pressure cap, change the thermostat and bleed the system before doing anything else.
As for the dipstick, is the engine cover loose, ie, have some of the rubber mountings broken, if so then the engine cover is making the dipstick rise up....common problem.

hi thanks for your replies. Yes the cover is loose so thanks its prob that! The owner that sold me the car (admitting the fault) had just replaced the coolant pressure cap hoping it was that, but to no joy. Yes its leaking from the sensor area and cap, presumably because these are the weakest parts of the pressure system. Would replacing the thermo do anything as its not overheating? I have bled the system but this makes no difference. After about 70 miles of good driving it has blown the equivalent of about a pint of water out of the cap and the low level light comes on.

Any more suggestions or advice would be most appreciated b4 i do summit drastic like removing the head? Really I would have like more clear evidence like the sniffer turning green/yellow.

One pint of water in 70 miles would lead me to believe the head gasket is alright, one pint in 5 miles would give me concerns.

The thermostat could be faulty, but also check the radiator for any cool spots when the engine is hot, that would indicate a blocked radiator.

Steve makes a valid point about making sure that you are not overfilling the tank.

yes, i agree, if it was over full i could see why the water would come out. But it has swollen pipes which releave when you take the coolant cap off and the low level light comes on, unless this is faulty?

Hmmm will check the rad for cool spots, and change the thermo and blled once more to be sure. There is def. no leaks however from anywhere. I even put a coolant pressure tester on and found no leaks.

Thanks for your replies again, any further help is most appreciated as i said b4 i dont really want to take the head off without some difinitive proof!

I reckon it could be the early signs of head gasket failure.

Have a read of this.......viewtopic.php?f=1&t=3814&hilit=tripped+ ... =15#p36944

Could be HG, may be worth sticking a bottle of K-Seal in. Bloody good stuff!

will k seal stop the HG from pressurising the system?

lazarus79 wrote:will k seal stop the HG from pressurising the system?

I don't know to be honest. I used a bottle on mine as I had signs of water in the oil; it cured this and it's been 1.5 years since I put it in.
Have a look on ebay for it, I got 2 bottles for £10 so not much skin off my nose if it did sod all.

Thanks for all your posts. Took the head off yesterday and sure enough it looks like a tiny leak between cyl 2 and the water jacket. Will put it back together sat morining and see if it works!!

Incidentally does anyone know the tightening sequence/torques of the new head bolts?

Always working from the centre outwards.... windscreen side 1, 4, 5, 8, 9....front of car, centre bolt...2, then, 3, 6, 7, 10.
Stage 1...20NM
Stage 2...60NM
Stage 3...220 degrees.

Maximum bolt length 133.4 mm.

fanstastic thanks for that. IF it fixes the prob ill post it up here so others may recognise the symptoms

Hi, for those that were interested this was the HG and the prblem is now fixed hurrah! will know now what to look for in future!!