Untracable water leak on stopping - suggestions?

[Nick]

Another problem with my non-turbo '86 is a curious water leak. The engine runs at normal temperature, if sometimes too fast because of ongoing idle issues, but on stopping, as the coolant starts to boil there's a significant amount of water vapour emanating from the engine. I've checked all hoses that I can find, and looked at the service manuals, but hoses seem fine. I'm wondering if it could be the water pump although the vapour seems to come from nearer the engine.

Looking over the drivers side wing into the compartment, the image marks the location where vapour seems to come from, flowing out from under the metalwork, between the curved pipes and the metal box below, and up, more or less directly below where the filler cap is. I briefly thought it was from the horizontal hose, but I think that's an air pipe? Anyway, it's not from there but flows towards there and of course up.

Any thoughts? Hopefully it's not a crack in the engine itself, and I'm really stuck on how to find it, let alone fix it.

http://www.ioncube.com/leak-021.jpg

Cheers
Nick

[clive]

Hi Nick,

Have you noticed any vapour from the back of the car , bad starting or misfiring until warm ?


All the Best Clive
e-mail: clive@mazdarotaryclub.com
web: www.mazdarotaryclub.com

[Nick]

Hi,

Yes, not really and maybe. There is vapour, but I think that there's always been and it clears fairly soon. No ominous smoke. The exhausts always smell bad, and people have started driving some way behind now, so the mixture may be all over the place. There have also been petrol fumes in the car on and off for ages but that soon clears.

Generally the car has been great. It's only previous owner was an ex-model who was in the cadbury flake adverts from the 70's(?), who'd looked after it, as I have too, but it's suffered from the fate of mostly short journeys.

No bad starting, and typically it starts instantly. Sometimes the car is a little rough on low revs but really the acceleration and deceleration is smooth, with very few 'pops'. My series 1 (now stolen) used to backfire spectacularly, and this is a marked improvement! There's another problem which is fast idling, and before that happened it had been rough on low revs after starting for a few journeys. I'd worked through setting the idle, (although possibly the wax pellets are at fault but I don't think that I found the fast idle unit yet to explore), but I hadn't jumpered the initial set connector. Despite that, we had the idle running better and nicely on low revs. However today after redoing the idle and jumpering the connector I had the idle revs lower again but it wasn't as smooth idling as it had been, and sometimes it would still hunt up and down between 1000 and a little higher. We'd also checked the bac valve and that wasn't stuck. However, certainly it's not right with the idling.

I assume the water is boiling when stopping because the pressure is lower in the cooling system, therefore the boiling point of the coolant is lower, and bingo, it's bubbling away. I also had the warning buzzer go off at one point until more coolant was added. It's never overheated, but the temp has been climbing quickly recently when it was idling at 2000 and I was stuck in traffic. On the move again and it cooled quickly.

With a few things now awry, I've booked it into Rotechniks, particularly as I can't locate the leak, and really it could do with other minor things too like new filters, oil change etc. It would be fun to explore more but I reckon there's not much more I can look at on my own now. Hopefully they won't say that's a waste of time because the leak is terminal. The only concern now is whether it's advisable to drive it to Reading (60 miles), with the inevitable vapour leak when I get there, or go a short way and let the AA tow it the remainder.

[clive]

Hi Nick ,

Sorry to be the bearer of but it sounds like you have had a water seal fail , which will mean a rebuild ! anybody else as l realy do hope l am wrong.

clive@mazdarotaryclub.com

[Nick]

Hi Clive,

Well I was prepared for something like that. Safe to drive 60 miles do you think or could it get dramatically worse and damage things? I'll give Rotechniks a call about that possibility, but any feeling for which side of £1K a rebuild could be? :) I wonder about the merits of a rebuild vs. maybe a replacement engine. Given that it's otherwise been fine it would seem a shame to bin the engine because of a water leak.

Nick

[Carl]

Hi Nick,
I think that Clive is right in that you probably have got a water seal failure.The high idle you mention could be due to this too as the coolent level has to be completely full to get the sensor to work for idle control.
If you do get a rebuild then it would pay to have it done properly with apex seals changed too.There are probably a fair number of other parts that will need to be changed too,so it will be quite expensive,but if the car is in good condition and you plan to keep it then a rebuild would be a better option than a replacement engine that is an unknown quantity.
Hope that this helps,
Regards
Carl

[Nick]

Thanks Carl. The car's not too bad, but does have some rust patches now and some other imperfections. Some window switches need cleaning, the fan switch doesn't always work, passed its last MOT but I think that they said that it may need new shocks next time, ...

But when it's clean it still looks good and has been going fine, and so even if it's £2K or so + some time to address the rust issues I wouldn't mind that much.

I'll have to wait and see what the verdict is later next month when it's hopefully in Reading.

Nick