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Discussion Starter · #1 ·
Hi Guys,
Long time reader first time poster,
I have only recently entered the 4x4 scene with the purchase of a 92 maverick carby Fed tb42 which needed some work such as swivel hubs, trailing arm bushes,valve stem seals, and a couple of other rubbers all of which I have done myself besides the stem seals thanks to the help of this forum it really is a great place with plenty of help and information.

So when my next little problem came up I thought I'd be best asking for some advice from the experienced people here before throwing money at the shop I hope someone can help.

So I had done the swivel hub seals and bearings on Saturday all went very well (a lot easier than it sounds) just time consuming anyway took it for a test drive parked in the driveway came out a hour or so later and noticed a small puddle of coolant sitting there under the diff,
Had a quick look underneath and it's leaking from a plate under the inlet manifold which has two hoses meeting a connector looking from above it would be directly below the carby,

So I left it till the next morning and tightened up the hoses started her up and noticed she was idling very low and trying not to stall auto choke seemed to do nothing so pulled on the manual for a bit and she picked revs up enough to run without choke but they are fluctuating by say 100revs or so from 550-450ish usually idles at 650-700 also picked up on a descent miss which is very noticeable and the leak is getting a bit worse but doesn't start leaking until shes up to operating temp.

It's really got me buggered what's going on as a coolant leak I wouldn't think would cause the engine to miss and play up as much as it is, it's not running hot or anything, also when I place my head near the intake I can hear a sound like a sort of gulping it's hard to explain but is coming from the head it's also blowing a lot more smoke than usual,

I haven't takin the manifold of yet but is it possible there could be a crack in the intake letting coolant into a cylinder causing it to miss and run like a pig ?

Before this she was running great besides the smoke on start up and a bit on decel carby has been rebuilt recently all leads and plugs also done although the oil passing the valve stems is getting the plugs fairly dirty.
Any suggestions advice would be greatly appreciated.
 

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Discussion Starter · #3 ·
Thanks for the reply I did a few checks yesterday,
Compression test comes up good no water in oil rocker cover cap isent under pressure. Is there any other checks I could do to rule a blown/cracked head. There's definitely no oil leaks coming from around the head either.
 

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I am fairly sure the TB42 manifold has a coolant cooled section under the carby below the plenum.

Also I think from memory, the inlet of the radiator coolant and thermostat housing is built into the front of the manifold?
SO you may just have a leak in the manifold gasket, or the coolant heater hose fittings in the base of the manifold, etc.
 

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Discussion Starter · #5 ·
Thanks geordie I will check the fitting if this is the cause how could this cause the misfiring and Bad idle? Most intake manifold leaks I have experience with dramatically up the revs by 600 or more but I am unfamiliar with this engine I will give it a good spray with some carby cleaner to see if I can find a leak before ripping the manifold of to sus out the fitting, I did put a 3 row alloy radiator in it a few weeks ago but I doubt this would have any effect on the systems operation.
 

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Thanks geordie I will check the fitting if this is the cause how could this cause the misfiring and Bad idle? Most intake manifold leaks I have experience with dramatically up the revs by 600 or more but I am unfamiliar with this engine I will give it a good spray with some carby cleaner to see if I can find a leak before ripping the manifold of to sus out the fitting, I did put a 3 row alloy radiator in it a few weeks ago but I doubt this would have any effect on the systems operation.

I was in at a local shop on Friday having some exhaust welding done.

While I was hanging around waiting I had a look at a TB42 from a GQ that was there having all the core plugs replaced due to a few corroding through. They had stripped and re sealed gaskets for everything from the inlet manifold, front covers, water pump and the cover bit around that, the thermostat housing and inside the manifold had quite a bit of corrosion.

The plenum bit under the carby looks like quite thick alloy but could corrode or pit through letting water into the intake. Can you see down through the carby with a torch?

If yours also has the thermostat in the front of the intake manifold then there must be a water jacket gallery or connection through into the head. You might have a leak from the intake to the coolant which is spitting coolant into the motor.

Can you take out spark plugs and see the top of the pistons for any strange colouration or crusty buildup. Any coolant making it out the exhaust (although it would be bad to be that much).

If it was a head gasket then when the motor is running, there would be more likely to be pressure in the radiator (take the cap off and check for bubbles or oil) rather than coolant leak into the cylinders untill the motor is switched off then some will bleed in.
 
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