Citroen Synergie HDI pressurising coolant, ignore or fix?

[mrtee]

Hi, my Synergie HDI is pressurising the coolant which I believe can only mean the head gasket has a small leak. If I drive with the cap loose it runs perfectly and I only have to top up the coolant every 200 miles or so. I dont have the time or skills to change out the HG myself, and the car is only worth about £1500. Do I get the HG changed at a garage? I suspect this would be very costly as it would involve removing the engine for access? (although not sure). Also whilst they are changing it they might as well do the cambelt, the coolant, get the head pressure tested etc. And the head could potentially be scrap anyway if it is corroded or cracked?

As it drives fine I am wondering what the implications are if I just drive it as is with the cap loose, I did read about someone on here who drove for 6 years like this with a Xantia and had no problems? Whats the chances of further issues?

Cheers.

[chinkostu]

get it pressure tested, that way you can find where the break is (i'm sure theres ways of testing that will show between which cylinders there is a break. if you think its only small you could use some of those "radweld" style bottles to bodge it. I say bodge, it fixed my 206 dumping its coolant! do you have oil in the coolant and coolant in the oil?

as for doing the HG, if the cambelt needs doing soon then it's the ideal time to do it all. otherwise its just a case of locking the engine, whipping the head off and sticking a new gasket in. not massively involved but takes time to do properly, hence the labour rates are always huge!

tbh you'll only be able to properly tell what needs doing when it has been stripped down. could just be the gasket, could be (like you say) a crack in the head however unlikely

[mrtee]

No oil in coolant or vice versa, have driven well over 1000 miles since noticing the issue. I did try some K-seal but it got spat out and didn't work, so will try another bottle but applied with the cap loose so it can't spit it out.
Can anyone confirm the labour rates for a head gasket change on this vehicle, and if the engine needs to come out for access? Cheers.

[ekjdm14]

The pour-in fix mixes (FWIW I'd only ever touch genuine K-Seal as it is great stuff in the right situation) usually will only work for mixing coolant/oil type failures. When it comes to pressurising coolant they can't hold it most times as it's fighting against cylinder pressures not just coolant/oil pressures, as you've found.

IMO in your situation buying more K seal is likely a waste of money and I'd just run with the cap loose & keep a sharp eye on the level. Diesel engines don't run hot enough to really need a pressure cap on the system anyway & there's also less chance of water being forced back through into the cylinder when the engine stops.

Instead of looking into a HG change I would probably start saving and buy a nice running, identical, replacement engine from a written off car and swap it wholesale. potentially cost less to do that (and change cambelt before fitting) and be quicker too, plus you can make more money back by stripping & selling off the good parts from the original engine. Just my 2p & what I'd probably do if I didn't have the tools/time/confidence to replace the HG myself...

That said, if you do have a basic mechanical knowledge/skill level & enthusiasm to learn, you could research it & do the HG swap yourself, it's really not that hard just have to work to clinical levels of cleanliness & be able to spare the time with the vehicle off the road.

[mrtee]

It does say on the K-seal website it should work for this scenario, but I agree its not that likely. Any idea what the risks are of driving it as is indefinitely? Will look into buying a used engine, but I guess there is a large risk the new engine is buggered?

[citronut]

although i agree K seal is very good, its unlikely it will sort H/G problems on a diesel,as the compression is far greater than that of a petrol engine,

also if a diesel H/G fails you dont normally get oil water/water oil mixing very often, as again the compression usually forces the gasses into the coolant system,

first thing i woulds do would be thoroughly bleed the cooling system

were are you located

[mrtee]

I live in France

[mrtee]

Whats bleeding the coolant system for?

[citronut]

Whats bleeding the coolant system for?

just in case at some point/time someone has drained or the coolant level has gone quite low, and it was just topped up, so trapped air in the system

[Peter.N.]

I had this problem with my last XM, with the cap screwed down it would blow the coolant out on a long journey but leave it loose and I rarely had to top it up at all, I ran it for about 3 years like that. Bear in mind though that if the system is not pressurised the boiling point will be lower but presumably you are only driving it gently, its full throttle and high revs that will expel the coolant. If you are still loosing it with the cap loose and driving gently the head gasket will need doing.

If the car is good otherwise have a shop round for head gasket replacement prices, I haven't done one on an Hdi but they dont look to difficult.

Peter

[mrtee]

I only bought the car recently, and it has only covered 75k miles. Yet in the service history it has had the HG done at 45k miles in 2009. There is a bill for HG, skim etc. If it has gone twice already and I pay to get it done again (assuming it can be skimmed again if needed??) then what's to say it wont happen a 3rd time? he paid £700 for the head work and new timing belt. As I said I just bought the car for £1500 and don't want to spend another £750 on it if its likely to die again in a few k miles.

I think I have bought a lemon

[Peter.N.]

Sorry to hear that, you have been very unlucky, its rare for an Hdi gasket to fail, mine have done 200k and 232k respectively with practically everything original including the clutch and DMF. XUD gaskets used to fail at around 150k but although I have seen failed Hdi's its the exeption rather than the rule.

If you do think about doing it I would get a secondhand head. Get yourself a C5 you can buy a replacement car for less than the cost of a head gasket.

Peter

[mrtee]

Problem is I need a 7 seater that I can use as a van as well so a C5 would be too small. Do you think the head is no good if it has already been skimmed once?

[citronut]

is the rad fan cutting in at all, do think head gasket route until the coolling system has been thoroughly bled through, just to make sure its not just trapped air in there somewhere,

[mrtee]

Im happy to have a go at bleeding the system, can anyone recommend a step by step guide to this? Although I don't understand how it has suddenly got air in the system. I also spoke to a local mechanic and he said don't bother with a new HG as the head has already been skimmed so he cant warranty the work.

Does anyone know the implications of driving the car indefinitely with it like this? I drove to London and back the other day over 1000 miles and only stopped every 200 miles to top it up, and the guy I spoke to reckoned the problem wouldnt get any worse?