gas converter freezing over

[3jcorolla]

Hi,
I have a gas convertor that keeps freezing over. It is connected to the old throttle coolant pipe near the thermostat and feeds back to the top of radiator on the drivers side. It is an Aussie b2. I have a brand new radiator and thermostat. Engine has been bleed of air. If I pull the convertor outlet off the radiator water will flow out when I put the pipe below the level if the radiator (i.e. No blockage). As soon as I start up on gas what was a flow due to the water head soon turns onto a dribble as the convertor freezes over. It would seem that the water is not getting pumped through. Does the thermo stat need to be open for water to flow through this pipe? It would seem the water pump is not pumping water through. However I inspected the water pump and looks to be in good condition. Any thoughts? So far I am thinking either water pump impeller stuffed (impeller looked like new) or convertor stuffed?

This is on a disco 1 3.9

Any help appreciated

Roger

[bee utey]

I've connected plenty of converters to the throttle body heater circuit without a problem. However I always make sure the TBH is taken out of the circuit and use 10mm hose instead of the original 8mm. The flow through this hose comes from the space behind the thermostat so the flow rate is highest when the thermostat is closed. I've seen plenty of cases where the thermostat slipped down during fitting and leaves a large gap for coolant to flow direct to the rad. A thermostat should be stuck into the manifold with a dribble of super glue around the edge to stop this happening. Also some people drill holes through the thermostat skirt, this is counterproductive as the TBH hose does the same job but better.

Things to do: Take the TBH hose off the manifold and poke down the fitting to see if it's fully clear. Blow through the hoses and the converter to see that they are also clear. Ditto the fitting into the top of the rad. I've seen them soldered shut. You should be able to observe the strength of the coolant flow on a running, cool engine with the rad filler plug removed.

Switch the gas on without running the engine. Drop one converter hose into a tin of water and stick your finger over the other hose end. Look for gas bubbles from the converter. It may need a kit through it. I've never had much respect for these things, most died early.

[3jcorolla]

Bee utey,
Thanks for your reply. Currently I am using 10mm hose as you suggest with the throttle body out of circuit. When I put the thermostat in, I did as you suggested,i.e. Glued in with a small amount lock tight to keep it in. I have done the flow checks you suggest, what I have found is although there is a clear path through the system water is never really pumped out of the manifold out let, and only ever drains out. I suspect this is not a gas issue so much as a engine coolant system issue. I don't see the strength of coolant flow through the radiator on a cool engine despite a almost new looking impeller on the water pump.

I may have to change this water pump despite it looking ok.

Roger

[3jcorolla]

I always like in when people post their solutions and perhaps people can tell me if I am wrong.

I changed the water pump to no avail as I suspected but at least it is a known quantity now. I pull the thermostat out and run the car with no thermostat, and you can certainly see the flow. With the new thermostat out I compared it to the original (btw when tested wouldn't open no matter how long I boiled it). The new thermostat by cpc (same part number as a holden apparently) has ~ 2mm hole with a rattler through it to assist in burping (this makes the flow area more like a 1mm hole). The original thermostat (it says made in UK) has a 5mm hole in. So I drill a 5mm hole in mine and position up the top. Low and behold heaps of flow now going through at idle. And the gas has no sign of freezing up. The smaller hole probably does not affect a vehicle running purely on petrol. But when you a relying on flow, until the thermostat opens, on LPG a larger hole certainly helped in my instance, others experiences may vary.


Note that each time I played with the coolant system I burped the system for a long time ensure there was minimum air in the system.

Roger

[chopper]

Why wouldn't you just T it off the heater pipes or better still if there is no heater tap then run the water in series with heater circuit , That's how mine is on the V8 County. That stopped mine from freezing , it was Tee'd originally but it was easier for the water to pass through the heater core than the convertor so the heater got most of the heat. But now in series it gets full flow through the convertor also.