C15 diesel rad madness...

qunvat · Post by **qunvat** » 06 Sep 2005, 08:44

Hi there ....
Am new to this forum, (not new to forums as i spend far too much time on the zclub looking for advice on my Datsun 260z!)...anyway I have a '94 C15D van which is doing my heed in...heres the symptoms:
The rads been leaking via a small hole at the top for ages....a bit of radweld here and there and its been very drivable.
Last week it decided to turn into a hose pipe, and rather than than the usual trickle, it stated p*ssing out at a great pressure.
I used it for a short while, topping up at all times.Thought it was just the rad gone for good.
Bought a reconned rad this morning, and having never changed one B4 and after taking pics of the old set up, fitted it (with heater dials set to 'hot'...and WITHOUT any circlip plyers!!ARGHHH)
All well as I started her up. tried her a little later on and noticed water p*ssing out of one of the hoses. Put the circlip on properly.
Stated up again...this time after a few mins the water was leaking somewhere else (the side of the new bloody rad!)....took expansion tank cap off...woosh...a huge amount of bubbles at a great pressure.
Yes bubbles...just like someone had put fairy liquid into it!.....found the bleed nipple next to that 'pump' thang and relieved some pressure.
Waited until it seemed fairly constant and put cap back on....this time bubbles from the other side of the rad!!......drove it round the block to see if the fans were working ..they were.Gently relieved the cap,the pressure was HUGE with my bubbles everywhere!
...Does this sound like an air block??..OR a thermostat prob (just where is it anyway??)....OR even a water pump malfunction (having said that would water pump outta the bleed nipple if so??)
Oh my God, does anyone live near Cardiff?!..I gotta go to work by Wed at the very latest!!
Thanks fer listening, Simon (Cardiff)

xantiav6 · Post by **xantiav6** » 06 Sep 2005, 12:36

Sounds exactly like a blown head gasket. I think you had better get the 260z on the road...

Post by **RichardW** » 06 Sep 2005, 12:51

Sadly it does sound as if your excursions with no water have cooked the head gasket. However, the C15 does need quite a substantial header tank to get it bled properly. Cut the bottom off a large squash bottle that will fit in the filler neck, and jam it in the filler neck tightly, possible with some PTFE tape. Now fill it to the top (cut off bottom, if you follow!) and open the bleed screws to get as much air out as possible. Now start the engine*, and keep the level topped up as the engine warms up. Watch out for a load of air as the thermostat opens. Once the fans have cut in and out a couple of times, switch off and let it cool down. Remove the bottle and take it for a run to see where the level has got to.
* I suspect you won't get past this stage, and will find lots of bubbles entering your header tank, indicative of the failed gasket.
Other pointers for the head gasket are rapid pressurising from cold start and the system still being under pressure when the engine has cooled down.
Bad luck, but I think it's going to be time to be getting the serious spanners out!

qunvat · Post by **qunvat** » 06 Sep 2005, 16:00

Rich ...do you mean TOP of a squash bottle mate??? ..so i can fill the EXPANSION tank (no filler cap on rad itself)
Nice one , Si

AndersDK · Post by **AndersDK** » 06 Sep 2005, 16:46

With (normal working) hot engine the cooling system pressure stabilises to some 1-1.5bar controlled by the filler cap.
This slightly high pressure actually raises the coolant boiling point considerably preventing the coolant boiling inside the cylinder head.
At the moment you release the cap - the cooling system pressure equals out, the boiling point instantly decreases, and the coolanr instantly starts boiling. And THEN the pressure raises - pushing out the coolant [;)]
It is quite correct that under special circumstances the heavy bubbling from the coolant filler neck is a blown HG indicator. But only while observing this :
Engine must be cold (VERY important !)
Remove filler cap.
Start engine - let idle.
Now play with the accelerator.
If bubbling follows amount of acceleration - HG shot.
If nothing - but a few micro bubbles like from coffee when you add cream powder - all is well.
NEVER remove filler cap when engine is hot [8] !
The cooling system will boil out itself - you get scalded - and you are fooled to think the engine is shot.

Post by **RichardW** » 06 Sep 2005, 17:48

Si, yes, not very well explained! Cut the bottom off, invert the bottle and stick the top (where the lid went!) in the filler neck - this then leaves you a nice big hole (where the bottom was) to pour the coolant into.

qunvat · Post by **qunvat** » 07 Sep 2005, 02:07

Thanks all....bubbles bubbles and more bubbles...constant, after ten mins it was worse with the accelerator linakge pulled....like frothy coffee x 10,000
Scrappy coming in the morning!
Si

qunvat · Post by **qunvat** » 07 Sep 2005, 04:26

p.s on the look out for a good cheap reliable van now!
Si.

fastandfurryous · Post by **fastandfurryous** » 07 Sep 2005, 14:27

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by RichardW

Other pointers for the head gasket are rapid pressurising from cold start and the system still being under pressure when the engine has cooled down.
<hr height="1" noshade id="quote"></blockquote id="quote">
Rapid presurrising from cold start I agree with, but usually if an engine holds coolant pressure for a fair while after cooling down, this indicates that it's in good condition surely? If the head gasket has gone, then the coolant pressure will be lost through the gasket, putting coolant into the bores.

Post by **RichardW** » 07 Sep 2005, 17:33

"but usually if an engine holds coolant pressure for a fair while after cooling down, this indicates that it's in good condition surely? "
No, normally you open the filler cap and the whole system is at atmospheric pressure. You then heat it up, and the water and air expands, and the system becomes pressurised to maybe 0.5 bar. When it cools again the water and air will have contracted and there should be no pressure left.
With a HG leak, air / combustion gases are forced out of the cylinders into the coolant system, causing the bubbles and the rapid pressurisation of the system. The system now runs at the radiator cap relief pressure (about 1.5 barg) and the cap simmers, letting out the excess air being forced into the system. Now when you switch off, the air and water contract, but the system remains at elevated pressure due to the excess air that's been forced in there. Generally with minor HG leaks the XUD suffers, there isn't enough pressure in the cooling system to force water back into the cylinders to reduce the pressure (and in any case this might take a cylinder full!), so you find pressure in the system even when it's been stood a day or two. My BX TD did this for at least 70,000 miles before I finally took the head off.

fastandfurryous · Post by **fastandfurryous** » 07 Sep 2005, 19:18

Interesting. Every XUD headgasket failure I've ever dealt with has always been just as you describe, but they were unable to hold any pressure for more than about 5 minutes after switch-off.
Conversley, my 405 TD, which had a headgasket done 10k ago, and is fine, will hold an (albeit very small) amount of overpressure for at least 48hrs.
But then every head gasket tends to fail in it's own special way!

Stinkwheel · Post by **Stinkwheel** » 08 Sep 2005, 00:30

I had a xantia that filled it number 2 cylinder. When you wanted to start it, remove no 2 plug, syphon off water, refit plug, start car.
When i eventually took off the head (had owned the car 3 weeks and was doing it the whole time) i found the head really badly erroded, so if you have a head gasket go, get it sorted ASAP cos thats what ghappens when you leave it, i scrapped the car as it had a few other faults and had been in a bump and repaired poorly, i should never have got it but it was CHEAP.