overheating 4.6

[RGD129]

hi everyone.

not long ago i brought a 2000 p38 that had been overheated, the plan was to rebuild rangie for the wife.

i finished the rebuild a few days ago but the engine still overheats at random.some times while idleing the guage will sit at half way then the needle will go all the way too the end of the hot zone then the exp tank will start boiling before i can turn engine off and other times after 10 minutes of driveing.while rebuilding the engine i got the heads overhauled and crack tested and checked the block for cracks and damaged liners.

i have tryed two thermostats (one was brand new) that i check in a pot of boiling water before installing them and still the rangie overheats.ihave bleed systems about 2-3 times after making a change and im using a 50/50 mix of coolant.ive replaced the exp tank cap, the water pump looks brand new, the radiator was replaced 3weeks before i brought rangie and the fan is pushing heaps of air (gets harder to turn by hand as it gets hotter)

i have taken the thermostat out and the temp guage sits at half way after driving for a while but i want to do a bit of towing so i really need to fix problem rather then bandaid it.

any help or info would be a great help

regards brett

[bee utey]

Probably still a cracked block. I wouldn't touch a used 4.6 without replacing the liners with top hat types. Too risky. Removing the thermostat just leaves a quick path for gases to vent via the pressure cap. Have you had the cooling system tested for combustion gases?

[RGD129]

ihavent had cooling system checked for combustion gases.is it done with exp tank cap off and a gas meter that measures co2 and o2?

the block has stepped liners.

regards brett

[LRTech23]

It's a p38... Not really much more to say.


Haha

[PeterAllen]

May not be relevant to your situation but make sure you dont have any blockages in the coolant header tank pipework. I had overheating issues some time ago and found the thin metal pipe in the header tank was blocked with crud. Can test by undoing small diameter hose from radiator top left that goes back to header tank and make sure airflows freely. Unblocked mine with a compressed air hose hooked up to it and cured the overheating.

[PhilipA]

The radiator was replaced 3weeks before i brought rangie and the fan is pushing heaps of air (gets harder to turn by hand as it gets hotter)



Does the radiator look NEW and can the seller provide a receipt or maybe the seller got one from the wreckers that is clogged inside. A quick coat of paint and Bob,s etc.
Regards Philip A

[bee utey]

A radiator repairer should have a tester. I've not had it done because the signs of coolant blowing out are obvious enough on their own.

One mod I did to a cracked D1 engine was to replumb the 8mm hose from the top of the manifold (goes via the throttle heater) into the top of the expansion tank via a screwed in hose connector. This way the only path for combustion gases is to the vapour space under the pressure cap, and it blows off without losing much coolant.

Other than that I believe its possible to fit the thermostat the wrong way around on those engines with predictable results.

[LRCounty]

ihavent had cooling system checked for combustion gases.is it done with exp tank cap off and a gas meter that measures co2 and o2?

the block has stepped liners.

regards brett

Brett

Did you have the stepped liners installed? Or the previous owner?

When installing stepped liners, it is imperative to either clamp the liners down while the block is cooling, OR press them home after cooling. The thicker flanged bit at the top actually expands longitudinally by about 8 thou of an inch when dropped into the heated block. The engineering shop should machine the step in the block to be slightly less than the stepped flange height, record accurate measurements of both, then measure how proud the liners are from the block after everything is cool, to ensure they are fully home. Then the block can be decked and the engine built with confidence. Otherwise the liners will press home under the pressure of the head gasket when it reaches operating temperature.

The above summarizes my own 12 month drama, with me stripping the engine down twice during that time. The solution (touch wood because it is currently running fine) was facing the block AGAIN to the same level as the liners.

I hope your problem is simply a blocked radiator or pipe as suggested previously.

All the best
Andre

[RGD129]

thanks for all the info

the small breather on the radiator is spitting out water when the rangie is running.i can see it dribbling out when the engine is running with exp cap off.

the 8mm hose from manifold is running to the bottom of the exp tank atm but ill try moving it up near cap.

the liners were put in before i got the radiator.

ihad tryed puting the termostate in the top hose and it ran fine for 2 day but over heated today after 86kms

thanks again for all the feedback and info

regards brett

[wayneg]

the small breather on the radiator is spitting out water when the rangie is running.i can see it dribbling out when the engine is running with exp cap off


When the engine is running you should get a fairly constant steam comming through from the Rad to the expansion tank, as advised make sure its completely clear of blockages.


the 8mm hose from manifold is running to the bottom of the exp tank atm but ill try moving it up near cap.

Not sure if you have a Gems or Thor engine ( should be Thor in a 2000yr car) but you can run the hose from the base of the expansion tank direct into the block at the front of the valley. On the Thor you need to remove the alternator to get access, not sure on gems. This by passes the intake heater, a source of many small leaks.


ihad tryed puting the termostate in the top hose and it ran fine for 2 day but over heated today after 86kms

I presume you connected all the lower hoses without the sputnik thermostat, then fitted a thermostat into the top hose? I am not convinced this is a good idea until the car is running cool before you start changing things around from standard spec

These cars are a real pain to get all air out of the system after working on the cooling. My method is to raise the front of the car, fill with coolant, expansion cap off, run the car for a few minutes keeping an eye on the expansion tank. Dont let it overflow, turn the car off as soon as the level starts to rise. Leave the car for several hours and the coolant gets drawn into the system. Repeat several times until the level does not drop.

Are you 100% sure the rad is not blocked? even a new rad will block up if the previous owner has stuck a load of sealer in there to cover up leaks for a sale. Its easy enough to remove for a flow test.

[RGD129]

hi wayneg
im getting more of a dribble out of the rad exp tank rather then a constant stream.would this indicate a worn water pump or air in the system?

the 8mm hose runs straight from the thor manifold to the bottom of the exp tank atm, the hose had been run this way before i brought rangie.

if the radiator was blocked wouldnt the temp guage rise at a constant rate? my temp gauage sits at half way for a while than at random goes into the red and the light comes on in 2 seconds so i turn rangie off but, if i start rangie back up after 1 minute the temp guage is back to normal.this is really doing my head in.

thanks for the help

regards brett

[benji]

Does the thor system have a seperate coolant sensor for the guage? The GEMS (thus RRC) ones can be really bad. Does it seem to run lean when this happens (loss of power, little throttle response)? I just can't see the coolant termaperature genuinly heating up that quick. Air under a coolant sensor will also cause the same thing.

[parasnoop67]

Hi Brett, the wacky temp guage is possibly an electrical issue, easily fixed.
When I bought my 96 gems the temp guage was erratic and a new wire from the battery to the engine block fixed that.
Just recently I had a similar issue but different. When the air conditioning was turned on the temp guage would climb rapidly but the motor wasn't hot, just the guage said it was. A new earth wire from the alternator to the battery fixed that one, so worth a look.

[RGD129]

hi all

the coolant temp sender is in the intake manifold next to a 8mm hose that runs to the bottom of the exp tank.idont think that it is an electrical problem as when i turn the engine off i can hear the coolant boiling in the exp tank but i will have a look at the engine earth.

thanx brett