Long Term Coolant Leak (Air Lock?) Problem

[Grim.Badger 15]

Since I bought my current GTi in 2009 it's always, eventually, spat out around 2L of coolant as if I had a pinhole leak in a hose somewhere - but I could never find one. Now it spits it out almost instantly... I've tried resealing the thermostat housing, which was leaking oil but apparently not coolant, and the plastic connector on the lower back of the engine. The heater matrix provides a good, consistent heat (so I'm guessing its not leaking), and the radiator is a relatively new aluminium unit. Some of my hoses are new, some are old, but none appear to have holes or splits. There is scaling on the outside of the two pipes going into the TB, but I don't think that's causing any issues. I replaced the water pump and gasket a couple of years ago with no difference to the problem.

 

I do know that the expansion tank (P2 black square tank) isn't as well sealed as it could be. I stupidly tried a p1.5 cap once, wondering if somehow the cap was causing problems, unfortunately it caused the system to over-pressurise and coolant sprayed out of the seams of the tank (I'm guessing I could also have blown other seals).

 

As well as the damage that I could have caused (above) the previous owner also used a poor quality sealant all over the car so there is a chance that the bond between the inlet manifold and head is poor. Could that cause this problem?

 

I've always wondered if there is a leak around the HG, or possibly the liners, but I'm guessing that after 7 years something would have gone really really wrong if this was the case.

 

Other than checking over everything again, and replacing the expansion tank, is there anything anyone can suggest?

Edited May 29, 2016 by Grim.Badger

[toolie72 67 1 Cars]

Well you need an expansion tank that holds pressure or your water will be too hot, water at a higher pressure has a higher boiling point.

Any signs of water in engine bay?

Well known point is inlet manifold to head join

Small s shaped hose to sad also as its hidden below distributor

If there's no sign of water at all then engine must be eating it-do a compression check

[welshpug 1,622]

ph1 caps are the same, do if the tank leaked on the seams then its a knackered tank, ive seen it before on the Saxo i service for, tank blew in half!

 

inlet to head should be gaskets not sealant, though the thermostat housing to the head on later engines are sealant not a gasket.

[steve@cornwall 100]

My first suspect would be the blind waterways under the inlet manifold.

[Grim.Badger 15]

ph1 caps are the same, do if the tank leaked on the seams then its a knackered tank, ive seen it before on the Saxo i service for, tank blew in half!

 

inlet to head should be gaskets not sealant, though the thermostat housing to the head on later engines are sealant not a gasket.

 

It was a p1.5 cap, on a p2 tank - didn't work

 

Other gaskets on the car have had sealant on them as well, so I expect the same with the manifold-head joint. I would be happy to be proved wrong!

 

There's no obvious leak in the engine bay, no water or coolant staining. I've had all of the hoses off several times and they all seem solid with no signs of leaking (I've had pinhole leaks on previous GTi's so I'm fairly certain I know what I'm looking for).

 

Essesentially, the system is acting like it has an air lock. When I refill the system, bleed it, and turn the engine on with the cap off the coolant rises more than it should and eventually overtops. Tom Fenton saw for himself what it does, when it embarrased me by coughing up about 1L of coolant on his garage floor

[toolie72 67 1 Cars]

Hmm suppose you could drain it when you change tank, then measure (with kitchen jug-put it back!!) how much it takes

Say it only took 4 litres you'd know then for defo you've got an airlock/blockage-would tying tank higher up overnight maybe help it burp?

Does coolant smell oily/petroly (I know that's not a word)

[welshpug 1,622]

all gti caps are the same, so i think its just masking the problem that your old one was weak.

[Grim.Badger 15]

Hmm suppose you could drain it when you change tank, then measure (with kitchen jug-put it back!!) how much it takes

Say it only took 4 litres you'd know then for defo you've got an airlock/blockage-would tying tank higher up overnight maybe help it burp?

Does coolant smell oily/petroly (I know that's not a word)

 

It takes the full amount. No petrolly or exhaust smell, or sheen on the surface. I forgot about the trick of raising the reservoir! Thanks

 

all gti caps are the same, so i think its just masking the problem that your old one was weak.

 

If you're sure The P2 cap looks like it has a different height (if that makes sense). I'm getting a new tank anyway.

[DamirGTI 325]

If new cap+tank wont do any difference , i'd do the chemical 'block test' (might be small , hairline crack in the head or the liner) .

 

 

D

[Grim.Badger 15]

Something is much worse since my last tinkering, I was in traffic outside Sheffield today and the cooling fan didn't seem to come on when the temp went almost to the top, suggesting that water level is going below the switch on the radiator (or the temp guage is somehow over-reading). Needs investigating this weekend!

[Grim.Badger 15]

Update - the tank has a split/crack in it I'm also going to check over all the pipes (again). The coolant fan wasn't coming on because of a wiring fault, now fixed.

[toolie72 67 1 Cars]

BIG torch, get head under the sump, check for cracks on back of block, I had frost crack (in storage-my fault entirely) which looked like a hair

Got worse over about 6 months until I started blowing hoses at random, managed to keep it going until my promised engine materialised, mine was pressurising coolant which I couldn't get my head round-surely it would p@@s out the crack but no it would pick the weakest hose

[Grim.Badger 15]

Update - fitted a new expansion tank, seemed fine for a couple of days but then I started to get issues with starting the car. I figured out that the king lead was loose, but that didn't completely solve the problem. Coming back home today, I started to get a misfire and lots of white "smoke" out of the exhaust. Coolant temp and oil temp were fine. I checked the chambers just now and one was full of coolant (which is now all over the garage)..... I'm really hoping this is the manifold garket, not the head gasket.

[toolie72 67 1 Cars]

Compression check time I think

Failing head gasket could explain your water trying to over pressurise, white smoke/steam is normally a bad sign out of exhaust but if you were moving and a hose had gone it could I suppose look like its coming out the back

Not sure I understand what you mean by chambers tho?-if you mean spark plug recess I'd check hoses beside it-or that cylinders filling up-the pressure build up if cylinders filling with coolant will be astronomical, you could even bend conrods

Take plugs out-one obviously different in appearance, with a corresponding difference in compression=head off

It's not hard-it's just not fun

[Grim.Badger 15]

There was about an inch of coolant on top of one of the pistons (second from the flywheel), and in the inlet manifold itself. When I undid the nuts on the inlet manifold it just fell off...... The gasket had only bonded in one small spot. I didn't want to do a compression test with coolant leaking into the manifold, but may try it now that the system is drained.

 

The car has always had a teeny misfire that would randomly come and go, I thought it was an electrical thing, and the spark plug on this cylinder has always tended to be blacker than the others, which I thought was an oil thing. Maybe all this time I've had a leaky inlet manifold that was being disguised by my knackered expansion tank?

[Grim.Badger 15]

Here's how the mating faces look, bear in mind I have not cleaned them up at all, this is how it came apart.

 

 

 

 

 

 

[steve@cornwall 100]

Post 4??

[Grim.Badger 15]

Post 4??

 

It does seem that way Steve, I just wanted confirmation that the symptoms are right for that It looks to me like there is pitting around the two "blind" holes on both the head and inlet, where coolant has been leaking through.

Edited June 20, 2016 by Grim.Badger

[steve@cornwall 100]

It's actually quite a relief to see that when you've been losing water/misfiring/ getting white smoke.I've actually bought a couple over the years "needing head gasket" to find the new inlet gasket does the job. Fingers crossed because it looks like it may well sort yours.

[Anthony 1,000]

While it's apart, take the opportunity to tap those two waterways and blank them off with a couple of grub screws. I think from memory I used M8 sized ones when I did mine.

 

(no pictures to hand, but from memory Tom Fenton describes and pictures the job in his 1.6 Turbo thread if you do a search)

[toolie72 67 1 Cars]

Yes it's m8.

Holy dodgy manifold fitting batman-looks like the gaskets been fitted on top of the corroded part round the waterway

Get that gasket fitted (after blocking waterway) and hopefully breathe a sigh of relief

[Anthony 1,000]

Hmmm, I hadn't spotted the extent of that corrosion when I saw the pictures on the phone.

 

I'm not sure how well a gasket will seal with that amount of pitting. I think I'd be tempted to replace the manifold (as that looks like it's suffered the worse of the corrosion) given that they're so cheap for 8v's and use a decent RTV sealant rather than a gasket.

[Grim.Badger 15]

I have two spare inlets, so no problem there! I'm not sure the corrosion is as bad as the pictures make it look, I'm going to be looking at it again in a minute.

 

Unfortunately I don't have a tap, or grub screws

[Anthony 1,000]

It's not the end of the world if you haven't, as clearly the gasket or sealant should seal them up without issue and Peugeot themselves were happy to do it that way.

 

It's just something I like to do when the inlet is off to remove any chance of it leaking, plus it means that if you have to remove the inlet again in the future you don't need to part drain the cooling system first (well, assuming you haven't plumbed the throttle body heater in anyway)

[Grim.Badger 15]

I gave the mating faces a clean-up and the corrosion is extremely minimal, more of a discolouration of the metal, and the spare inlet manifold I checked was actually worse!

 

On a slight tangent, I noticed that the manifolds have blanked-off holes/projections that match up with the holes in the cylinder head. Also, the two manifolds had different sized blanks even though they're both P1.5/P2 1.9 GTi manifolds!