BX 17 TZD with worsening cooling system problems

andycadabra · Post by **andycadabra** » Thu Jan 28, 2010 6:31 pm

After 2 months of problems and more than £200 spent on hose repairs and wasted on 'steel seal', car is at last running and back on the road, with its cooling system intact, but one small problem remains - there's still bubbling in the expansion tank, yet apparently no water leaking into the oil, or steam coming out the exhaust.
If I use it as it is, on the basis that coolant will occasionally escape through the radiator cap, could the worst of my problems be that I have to keep an eye on the coolant level?, or should I resign myself to head gasket repair?.
Here's a video of the current situation..

Post by **mat_fenwick** » Thu Jan 28, 2010 8:19 pm

Personally I'd be inclined not to chance things, and go for HG/head replacement or a good replacement engine. I don't know what use it is, but here's a photo of what my head looked like after similar bubbling through the expansion tank.

I've read that you *may* be able to get away with things by leaving the cap off, so as to lower the pressure in the cooling system, but I guess it depends on how much of an optimist you are...

jonathan_dyane · Post by **jonathan_dyane** » Thu Jan 28, 2010 10:45 pm

mat_fenwick wrote:here's a photo of what my head looked like after similar bubbling through the expansion tank.

Apart from a slightly cracked pre-chamber, I don't see anything wrong with that

Post by **mat_fenwick** » Thu Jan 28, 2010 11:24 pm

So those cracks wouldn't necessarily cause the pressurisation? I just assumed that they were deeper than you could see. It failed a pressure test anyway, so I got a replacement head in the end and fitted that.

jonathan_dyane · Post by **jonathan_dyane** » Fri Jan 29, 2010 12:12 am

Not those one's, no. The pre-chambers are actually a separate part of the head, made out of a different type of alloy, and in many older heads were replaceable. As the pre-chamber is only pressed into the head, a crack in the pre-chamber cannot extend into the head itself and so penetrate a waterway.

andycadabra · Post by **andycadabra** » Fri Jan 29, 2010 11:51 am

Thanks for the tip about leaving the cap off, Mat. I've wondered what the effect of that might be, and assumed that it would cause the water to boil, but will experiment.
I used the car to drive 2 or 3 miles yesterday, and the heater was being very erratic going between warm lukewarm and cool and back to lukewarm again. I thought it was a sign of losing coolant, but when I checked I was only able to top it up about a pint and a half.

The thing is the head gasket is only just over 2 years old, and I've only covered about 8000 miles on it, so I don't know whether that means it might as likely to be cracked block or head. If it is, is it possible to repair such cracks or would it mean a replacement head (probably not an easy thing to get hold of quickly), or in the case of a cracked block, a new engine?.

Mat, do I gather that your bubbling wasn't down to the head gasket, and that you're still unsure as to what was causing the bubbling?

Linegeist · Post by **Linegeist** » Fri Jan 29, 2010 12:13 pm

andycadabra wrote: but will experiment.
I used the car to drive 2 or 3 miles yesterday, and the heater was being very erratic going between warm lukewarm and cool and back to lukewarm again. I thought it was a sign of losing coolant, but when I checked I was only able to top it up about a pint and a half.

You DID bleed the cooling system - using them little bleed screws at the back 'n stuff - to get all the air out when you refilled it ..... didn't you?

andycadabra · Post by **andycadabra** » Fri Jan 29, 2010 12:21 pm

yes, as far as I know there's only one bleeding point on these - The black plastic cap on the top right of the radiator.
I don't suppose the system can be completely bled while the compression leak exists.

Post by **mat_fenwick** » Fri Jan 29, 2010 12:24 pm

jonathan_dyane wrote:a crack in the pre-chamber cannot extend into the head itself and so penetrate a waterway.

Ahhhhh.

Showing my stupidity here I think! I can quite clearly see it's not part of the head casting if I actually look at it.

That would suggest the crack is between the pen marks they made after the pressure test then. I'm just wondering now whether a leaking valve could cause a pressure test fail? Surely they'd check that...

Brian · Post by **Brian** » Fri Jan 29, 2010 3:35 pm

Now Mat, that is a very interesting photo.

Unless my very tired eyes deceive me, I detect a crack in the head between the inlet and exhaust valve seats.

I have had a head before with this fault, but with a skim, was reusable again for at least another 3k miles, when I sold it.

The buyer never came back to me with a complaint, so I guess it lasted well.

I do have another head from a turbo engine that has two of these faults.
(Will try and post a photo)

Has anyone else reused a head with that type of fault?.

andycadabra · Post by **andycadabra** » Fri Jan 29, 2010 3:42 pm

I wonder what caused bubbling in the cooling system then?

jonathan_dyane · Post by **jonathan_dyane** » Fri Jan 29, 2010 4:29 pm

Brian wrote:Now Mat, that is a very interesting photo.

Unless my very tired eyes deceive me, I detect a crack in the head between the inlet and exhaust valve seats.

I have had a head before with this fault, but with a skim, was reusable again for at least another 3k miles, when I sold it.

The buyer never came back to me with a complaint, so I guess it lasted well.

I do have another head from a turbo engine that has two of these faults.
(Will try and post a photo)

Has anyone else reused a head with that type of fault?.

This?

I didn't spot that, looks like a likely bet

In my defense, it does also look like an edge where the casting curves inward between the valves, but I guess it could be the offending crack...

Philip Chidlow · Post by **Philip Chidlow** » Fri Jan 29, 2010 4:33 pm

andycadabra wrote:I wonder what caused bubbling in the cooling system then?

My money would be on head gasket.

Brian · Post by **Brian** » Fri Jan 29, 2010 4:55 pm

Hi Jonathan,

The line you highlighted in the green circle, is in fact a machining line, the one I refering to, was above that line.

This is the worst crack on my spare head, but as far as I can see, with the aid of a bright light and magnifying glass, does not show up in either of the adjacent ports, so may not penetrate very deep.

jonathan_dyane · Post by **jonathan_dyane** » Fri Jan 29, 2010 5:06 pm

Brian,

That's what I initially thought the bit I have highlighted was. The only other bits I can see on Mat's head that could be thought to be cracks are the two 'ridges' which are again part of the casting on some heads (I have obscured the lower one with green on the pic I drew on) and what on first sight looks like a crack between the valves like on your head, but is in fact (I feel) a mark made in the carbon by something the head has contacted after it was removed (the mark clearly continues onto the valves...)

As regards your head, personally I would not put it on a car of mine, the crack is only going to get bigger until trouble does start. That said, it may well be some thousands of miles before this occurs!

Best,

J.