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View Full Version : Losing Coolant / Single Cylinder Misfire when Cold?



Cruiser
05-10-2015, 07:56 PM
Ol' faithful ('92 TR 2.6L) has recently developed an unusual issue. Noticed while coming home a couple of weeks ago that the temperature gauge was creeping up toward three quarters. I turned the heater on and increased the RPM to increase the coolant flow rate through the water pump, which did the trick - the gauge immediately fell back down to half. Close call.

Drove it back home and let the engine cool down. Opened the radiator and noticed that a significant amount of coolant was missing, I had to add about a litre to the system to bring it back up to the full level.

The car had been making some unusual rushing water noises behind the dashboard (http://www.aussiemagna.com/forums/showthread.php?t=104382&highlight=) for some time, but it seemed to come and go at random, often not occurring for months at a time.

Along with the loss of coolant, the engine has developed a misfire on one cylinder for the first 30 or so seconds after the engine is started. It'll run on 3 cylinders, and the fourth cylinder will cough and splutter for a bit before coming back online normally. The car then runs correctly on all four until the engine is shut down overnight.


I've quizzed a couple of mechanics on the matter and the same answer I've heard from all of them is that the head gasket could be leaking between a cooling jacket and a cylinder, slowly leaking coolant in the cylinder overnight and fouling the spark plug, which then burns off after the engine is started again.

I haven't yet had the chance to pull the plugs and look for the presence of anti-freeze in the cylinder, but that's next on the cards. I attempted to get ahold of a cooling system combustion gas tester, but haven't had much success there yet.


These people aren't Mitsubishi specialists though, and most of them haven't touched a 2.6L before, so I want to ask the opinion of the more knowledgeable people here.

At the moment it sounds like grim news for the Astron no matter how you slice it, and chances are should I choose to repair this car, I'd sooner throw another lower kilometre engine in there than attempt to repair the issues with this one. If I have to change engine I'll replace the water pump, radiator, hoses, fittings and everything in between at the same time. Have a lot of NIB spares left over from another car.


Thoughts?

magna buff
06-10-2015, 02:25 AM
Heater core leak under dash
but should have coolant leak and smell in /under the front carpet

Head gasket
Stuck thermostat
Old radiator cap
Soft hoses/ loose clamps
Suspect water pump
Coolant should be mixed with oil or co2 by now
Corrosion at the water jackets and head gasket
Head gasket blow between 2nd and 3rd cylinders

MadMax
06-10-2015, 05:48 AM
It will be corrosion between the water jacket and combustion chamber, only 5 mm or so between them.
Red rust on a spark plug will confirm it.
Just pull the head and get it tested for hardness, movement of valve guides, and if ok get it welded and refaced.

I always laugh a bit when someone says they will pick up a good low km motor and fit that - how old is the youngest version of the Aston 2, how long has it been sitting there, how hardened are the valve stem seals, and how much corrosion will it have?
Edit: the rushing noise in the heater core is normal when there is air in the cooling system.

Cruiser
06-10-2015, 09:15 AM
I always laugh a bit when someone says they will pick up a good low km motor and fit that - how old is the youngest version of the Aston 2, how long has it been sitting there, how hardened are the valve stem seals, and how much corrosion will it have?

Well, an engine in better condition. Fewer pieces of chain guides in the oil pan. Although I suspect that won't be all that easy to find either. lol Reconditioned Astrons are available, but I haven't been able to find one that leaves much change left over from $3800 fitted.

I'll remove the plugs and see how they look. If it's a crack between the water jacket and combustion chamber and the rest of the head checks out, I'll follow MadMax' suggestion and have it welded and refaced. Would probably like to have the cylinders compression tested and find out how worn the bores are as well.