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Cooling Woes!
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Author:  bnicho [ Sun Feb 21, 2010 6:20 pm ]
Post subject:  Cooling Woes!
In several other threads I have spoken of my cooling system woes with my Moke. Basically, it seems to be getting worse the more I drive it, for the last few months.

It's a 1275 High Compression A+ Auto engine and box from a 1990 Metro. It allegedly had 33,000miles on it in the UK before coming to Aus and going into my Moke (another 10,000 miles). It's running the factory oil cooler from the Metro too.

Now it creeps up to 7/8 on the gauge (or 110 deg C) and just stays there. Oil pressure then drops 20-30psi. It never actually boils, but it's getting very hot. Ironically it still runs beautifully though!!

- I've tried a "super-cool two core" UK radiator, a new alloy radiator and a Morris 1100S radiator.
- I've tried blanking sleeve and a gutted thermostat.
- I've tried retarding the timing and enriching the mixture.
- I've tried the stock fan and shroud, same plus a thermo in the inner guard and even one thermo behind the grille and one in the inner guard with no engine fan or shroud.
- The water pump is less than four years old and has done less than 10,000miles. I've used proper coolant all the time, so I have no reason to suspect there's anything wrong with that. I can also see the water flowing well with the cap off and the engine running.
- There are no signs of water in the oil. I've never noticed oil in the water, but I've had the radiator out so many times now and used so many different lots of coolant perhaps it never had a chance to show!
- I can't see any bubbles in the coolant.
- Compression is 195psi on all four (hot, throttle open).
- No sign of steam out the tailpipe.

The only conclusion I can come to, is that I have blown the head gasket at some stage and it's steadily getting worse.

Any other thoughts before I rip it's head off? :(

Cheers,
Author:  drmini in aust [ Sun Feb 21, 2010 6:31 pm ]
Post subject: 
By all means pull the head for a look, but I'd be adding a heater core behind the grille too.
Automatics get hot, this is why ALL Minimatics had the underbonnet heater (aka auxiliary radiator).
The driver's handbook states it is needed, ie don't run without it.
Author:  74snail [ Sun Feb 21, 2010 6:43 pm ]
Post subject: 
You seem to have run through a few different solutions, the only ones I can think of is remove the oil cooler and clean and flush it , and drain the cooling system and refilling with just water and rust inhibitor

the other source of heat is an exhaust leak at the slip join , it does'nt have to be a large leak to make a difference

my 2c
.
Author:  mini_mad_matt [ Sun Feb 21, 2010 7:13 pm ]
Post subject: 
If you have retarded your ignition too much it will heat up as well i believe
Author:  bnicho [ Sun Feb 21, 2010 7:49 pm ]
Post subject: 
No exhaust leaks. It's got a Cooper Freeflow type manifold.

I've tried timing between 3 and 10 degrees at idle (3 deg it runs like a slug!)

I flushed the oil cooler out before I fitted it, and it's had oil changes at 1500 miles max since. The Auto is not slipping except for some flaring on the 3-4 change, which is common.

Hmm, I don't have a heater fitted, or the bypass from the heater takeoff. Maybe I need to try that next.

The best combo of the lot was an 1100S radiator with the stock fan, shroud and the thermo. It worked fine except in traffic when it got a bit hot. Of course it must have more capacity than any of the other combos I've tried. Maybe it's simply a capacity issue, but the problem seems to be getting worse with time.

For example, on the day of Watto's big bum out last year I'd just fitted a UK super-cool two core with no shroud or stock fan, just the thermo. It coped until we got to the event, but on the way home when it was a bit hotter it climbed up near H again. Wierd! Since then it has steadily got worse. I said "crap UK radiator" and "borrowed" a chinese alloy one from Mick. Fitted that yesterday, gave it a run today in preparation for going to Ballarat on Friday and it decided to climb into the red again!

The coolant I have in it now is the Nulon red expensive stuff BTW.
Author:  Mick [ Sun Feb 21, 2010 7:53 pm ]
Post subject: 
Off with its head!
Author:  bnicho [ Sun Feb 21, 2010 8:02 pm ]
Post subject: 
It's head gasket alright.

I just had a brainwave. (Or is that a fart?)

I went out and started the Moke with the cap off again. At idle, no bubbles. But if I rev it a bit, bubbles galore! Seems like head gasket its the culprit after all. But I will check the water pump as well, while I have it apart.

It looks like I'm taking the Corona Coupe to Ballarat swap now. I wanted to take the Moke, but I can't be bothered working on it at nights this week.
Author:  drivinglights [ Mon Feb 22, 2010 1:01 pm ]
Post subject:  overheating
With bubbles in the coolant it may well be the gasket, but remember that at revs the water pump will cavitate and cause bubbles created by the low-pressure zone behind the vanes under cavitation.

I had no end of grief for year with my 998 overheating, yet strangely running fine and not showing signs of stress.
I fitted a custom 3-core, big-tank, herringbone-pattern radiator, modified thermostat, new rad cap, 10-row oil cooler, high-flow water pump and even an EH-holden heater core for extra capacity in the summer.

The thing that finally made all the difference? Pissing off the factory temp guage and fitting a good quality capillary gauge. :shock: ......wasn't running that hot after all. :roll:
Now, sitting in traffic on a 30°C day, she gets up to about 190°F and then falls back down straight away once moving.

I'd spend the $50 first and get a good gauge before ripping bits off.
Author:  drivinglights [ Mon Feb 22, 2010 1:02 pm ]
Post subject:  overheating
With bubbles in the coolant it may well be the gasket, but remember that at revs the water pump will cavitate and cause bubbles created by the low-pressure zone behind the vanes under cavitation.

I had no end of grief for year with my 998 overheating, yet strangely running fine and not showing signs of stress.
I fitted a custom 3-core, big-tank, herringbone-pattern radiator, modified thermostat, new rad cap, 10-row oil cooler, high-flow water pump and even an EH-holden heater core for extra capacity in the summer.

The thing that finally made all the difference? Pissing off the factory temp guage and fitting a good quality capillary gauge. :shock: ......wasn't running that hot after all. :roll:
Now, sitting in traffic on a 30°C day, she gets up to about 190°F and then falls back down straight away once moving.

I'd spend the $50 first and get a good gauge before ripping bits off.
Author:  bnicho [ Mon Feb 22, 2010 1:15 pm ]
Post subject: 
Thanks for the suggestion, but I've already tried borrowing the gauge from my race car (Pricol Capillary). It shows 110 degress C and that guage accurate based on the "stick it in boiling water" test.

I'm certain it is the head gasket, but I will check the water pump is healthy as well.
Author:  drivinglights [ Mon Feb 22, 2010 1:18 pm ]
Post subject:  overheating
Fair enough. That sounds pretty conclusive!

Did you say you're running a fan shroud on the rad? Made a big difference to mine when I refitted it.
Author:  sgc [ Mon Feb 22, 2010 1:30 pm ]
Post subject:  Re: overheating
drivinglights wrote:
at revs the water pump will cavitate and cause bubbles created by the low-pressure zone behind the vanes under cavitation.


Yes, but remember that these bubbles are caused by the low-pressure zone. As soon as the pressure increases (with distance from the impeller) the bubbles implode, leaving a little shock wave in their place. It's this shock wave which erodes the impeller and the plumbing around it.

No way you'll ever see bubbles caused by cavitation in the radiator...
Author:  drivinglights [ Mon Feb 22, 2010 1:33 pm ]
Post subject:  overheating
Ah, good point. Had forgotten that. Good thing I'm a chemist and not a physicist. :D

If it's the gasket, wouldn't the bubbles from the rad stink like exhaust?
Author:  bnicho [ Mon Feb 22, 2010 1:36 pm ]
Post subject: 
As above, I've tried:

- Stock engine fan and shroud, stock radiator.
- As above, but using larger Morris 1100S radiator.
- As above, plus 10" inner guard thermo sucking out, like a mid-90's MIni.
- Two core super-cool, with no engine fan or shroud, just the 10" inner guard thermo.
- Two core + Two thermos - one 7" behind the grille pushing back, one in the inner guard sucking out.
- Alloy rad + two thermos.

But none of these have been conclusive, as the problem has steadily got worse. I think I was masking the problem by steadily upping the cooling ability.

Anyway, I'll be happy if I can replace the head gasket and any of the above combos works. I love my Moke and I hate not being able to drive it far, for fear of cooling issues.
Author:  sgc [ Mon Feb 22, 2010 1:40 pm ]
Post subject: 
Mick wrote:
Off with its head!


+1 :D
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