Blown gasket, ok compression ?

[LDN-BLN]

Hi folks,

After years of no major engine-related problems my 1.9 dg has had a catastrophic turn for the worse...

The backstory:

Got stuck down a dirt track the other day where I parked in the local countryside to take a walk only to find that it was a one way in one way out situation, with no space to turn around. The track had semi-frozen ground and it was downhill and anyone who isn't lucky enough to have a syncro (most of us) knows how awful the traction our bricks have in this situation.

After much wheel spinning trying to back out and next to no cooling effect (The rad fan didn't come on and I was trying to keep revs low and therefore the water doesn't pump all that much around the system to my knowledge or maybe it was to do with the steep decline) the engine overheated and cut out with much bubbling into the coolant top-up tank. "Oh bugger" and other similar exclamations of frustration ensued.

The current situation:

Breakdown recovery home. External examination by eye from underneath, there is purple coolant around the head gaskets on both sides and droplets everywhere. Took the plugs out and they look fine, no sign of oil. Did a compression test which ranges from 124psi to 140psi (done cold as engine doesn't start, also had the throttle closed) - not too bad by my reckoning, the engine should still run at those pressures right? I'm now in the process of removing the engine to find the point(s) of rupture and find the remedy (hopefully just replacing gaskets/o-rings). Sloshed some fuel into the carb and the engine fires instantaneously then dies. Just trying on the fuel pump alone shows no sign of firing.

My question

Obviously exhaust gases are going into the cooling system (evidenced by the top-up tank filling up with coolant and bubbles of gas), yet the compression values seem ok, how is this possible? Anyone have any idea of where the problem lies from the above symptomatic description?

Thoughts and guidance much appreciated. Also note that I am kicking myself for a) going down the lane and b) not letting the engine cool down.

Cheers,
Pete

[SyncroMatt]

Pete, I can only comment from my own experience of 15 years or so ago.

My DJ engine bus started pressuring the coolant system and overflowing the catch tank. It ran well and didn't feel down on power, but after 10-15mins driving would blow coolant out and the warning lights would flash.

No external weeping at the head to case seals or elsewhere.

A block tester confirmed I had combustion gases in the coolant.

On strip down there was nothing really obviously, the heads weren't badly pitted or corroded, no broken studs etc.

I came to the conclusion it was the seals around the cylinder where it mates to the crankcase or where they slot into the heads. Certainly a seal kit later and it was happy.

From your cold compression figures you have over 10% variation. Is it just one cylinder that is down? I might be able to find my old compression figures.

Curious that it won't run on the fuel pump alone.

At the end of the day it isn't going to self-heal, you should be able to get it to temperature and do a block test. But I think you know the answer

Sorry Matt.

[Mocki]

WBX engines don’t have head gaskets as such , you have water jacket seals that seal the head to the block externally , containing  the water jacket , and compression gaskets inside the top of the barrels sealing the combustion chamber to the heads , one per barrel . At the bottom of the barrels are rubber "o" ring type seals that keep the oil out of the coolant and combustion area . 

so the appearance of coolant externally wouldn’t affect oil or compression . 
if you have combustion gasses in the coolant it’s not the water jacket seals , it’s usually a pin hole in the head .

it’s all a engine out strip down job, which ever is at fault . 
over heating can have damaged any or all , or none . 

you should get a "sniff test " to confirm if you have exhaust gasses in the coolant , and pressure test don’t to see if the cooling system is leaking internally . But whatever you do , you should find out why and fix the cooling fan issue .the temp gauge also sounds faulty . 

as for fuel issue, it could well be the mechanical pump diaphragm has fails, or more likely if you were struggling on a steep uphill in reverse crap from the tank in the filters .
check the cone filter in the carb inlet spigot first