Outer Limits 4x4 Board

Hello all,

I've got a SWB Mavrick with a TB42 petrol engine/auto combination. I've been having overheating issues since late last year that I'm finding hard to diagnose. Hopefully some of you mechanically minded people can point me in the right direction.

The story so far is in Sept last year I overheated the engine when 4wding when my fanbelts broke after I got a stick stuck in them. Once I realised what had happened (guage going out the top) I switched off the engine and a mate went to the nearest town for some new belts. We fitted them in the bush and the vehicle ran, however It was overheating on the way home and I was forced to drive at about 45km/h to keep the heat guage happy (about half way on the guage).

I was certain that I had done the head but when I took the car to my mechanic he couldn't find any issues with the head after conducting the usual tests. The radiator was clogged though and I was told that this can happen when you overheat an engine as it flushes all the gunk out of the engine into the radiator. The radiator, thermostat & radiator cap were replaced at this time and the vehicle seemed to run perfectly when 4wding or doing the day to day thing.

However when I tow my poptop camper I still overheat and I haven't been able to find out why. The vehicle will drive normally while towing (heat guage registering just below half to half) for about 45 minutes (depending on the hills) before it seems to lose a little power. The heat guage will then spike straight to the top of the guage within about a kilometer. I will then stop the vehicle and find coolant pissing out of the overflow bottle relief hose. This happens consistently at about 45 minutes and it doesn't matter if I'm on a flat, up hill or down hill section of road.

Below is a list of what I have since tested/replaced in trying to solve this problem:

1. Pressure tested the new radiator and tested coolant for exhaust gases (Radiator shop).
2. Replaced Hydrostatic fan clutch.
3. Removed thermostat and tested in pot of boiling water to make sure it fully opens & closes. Replaced with a new one that I also tested before installing.
5. Tested vehicle without a thermostat.
4. Replaced the new radiator cap with another one to eliminate the possibility of a cap with the wrong spring load.
5. drove the vehicle around towing the camper until I thought it was getting close to overheating (starting to lose power). I then parked it, removed the spark plugs while the engine was still hot and left it overnight to cool to see if any coolant would seep into the cylinders. The next morning after removing the coil lead and cranking the engine the I couldn't see any trace of coolant (which would indicate a head gasket leak) on the tissues that I had put loosely in the spark plug ports.

This weekend I will remove and check the water pump to eliminate that as a possibility as that is the only thing left. I don't think it is the water pump as I think that would give me a consistent overheating problem no matter what the conditions.

I think I have a head gasket problem that is so small it only shows up under load and at this stage I'm reluctant to have a dirty weekend putting in a head gasket kit until I can prove that that is the problem.

Any one have any ideas?

Thanks MEX

i think u answered ur own question

if you havent replaced your hoses do that, hot tired hoses pull themselves shut... possibly bypass the heater and see if thats clogged... headgasket

Simon

was it a new radiator? I don't have any faith in second hand ones. Unfortunately i reckon you should have gone for a 3 core. They work a treat. As far as cooking an engine, speak to rainbow warrior on this board as his was that bad that it was leaking water slowly into one pot and still ran ok and didn't run hot. The head was well and truely shot. Does it run rough. Milky oil? If everything else seems good with power and performance you need to keep looking with the cooling system i thinks. nearly always comes back to it. I'd be checking what the other guys said with hoses etc. Also therostats have been known to be crap out of the box.

It was a reconditioned radiator where they used the existing ends from mine and replaced the cores. Oil looks fine and so does the coolant. Replacing hoses is a good idea, will do that as well.

MEX

man sounds like you have a air lock.

Jes

How do I get rid of an air lock?

When I fill the radiator up I leave the radiator cap off and let the coolant bubble out until the thermostate opens. The level in the radiator will then drop and I will then top it up before puting the cap on.

Is this correct?

MEX

MEX wrote:How do I get rid of an air lock?

When I fill the radiator up I leave the radiator cap off and let the coolant bubble out until the thermostate opens. The level in the radiator will then drop and I will then top it up before puting the cap on.

Is this correct?

MEX

rock the car side to side on the suspension
abit before you put the cap back on , u'll find more air will come out

MEX wrote:How do I get rid of an air lock?

When I fill the radiator up I leave the radiator cap off and let the coolant bubble out until the thermostate opens. The level in the radiator will then drop and I will then top it up before puting the cap on.

Is this correct?

MEX

yup. also have ya heater on I was told

Head gasket, mine had exactly the same symptoms

have you actually seen the fan turning? at high speed?

but then she'd be cooking at 45k's and running good at high speed.

my dad wired my fans up one weekend, twin thermo's. had overheating issues saw a few radiator dudes and they all said: need new radiator. need better airflow. one guy wanted me to buy 3core aluminium one for $1100

went home and got my brother to crank it over while i watched and i noticed one of the fans turning the wrong way

did a bit of screwing around with the wiring and haven't had an issue since

sometimes it's the simple things. those radiator blokes probally noticed and were just going to fix the fans, wash the radiator and then charge me for a new 3core!

I tested the new hydrostatic fan hub to make sure it was working by getting the engine up to operating temperature and then trying to stop it with my hand (carefully). I could not, the fan had enough power to push my hand aside.

The old hydrostatic fan hub was buggered and I could stop it with my hand doing the same test.

Thanks for your input everybody, sounds like a head gasket. I will try replacing my hoses, eliminating air locks & inspect the water pump this weekend before I go to the trouble of replacing the head gasket as these things will cost very little except for my time.

Cheers MEX

For what it costs for a new heads etc, a good low k second hand might be the go. I know a guy who still has my spare engine that was only 110,000k (not you rainbow warrior) that he needs to offload cause he needs the cash. PM if you are interested and I can see what I can stitch up for you. It was a top engine.

yep head gasket dude had the same happen to me and its on its third

Can't you test for combustion gases in the coolant?

I tested the coolant for combustion gases (radiator shop) with no result. This is the main reason I am reluctant to replace the head gasket at this stage. I was hoping to find another way of testing the head which would prove without a doubt that the gasket is the problem.

Mex

You would spend the same time/money diagnosing the problem as you would just ripping the head off and replacing the gasket.