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[Davemate]

i have a 1994 cherokee 4 ltr
i have just replaced the radiator
as the old one had sprung a leak
the temp gauge normally hangs around the 1/4 mark
if i get stuck in traffic it will go to the half way mark but
as soon as i move off withing a couple off hundred yards its back to the 1/4 mark
heater works fine
now if i give it some stick them let it idol for a while i can get the temp between
1/4 and the 1/2 mark
when i switch the engine off the water in the expansion bottle will rise
and overflow
if i restart the engine
as soon as it starts the water level drops back down
if i wait a minute the turn it back off the will rise again a tiny bit then stop
i have never over heated the car in the tree years i have had it
but i have never put any antifreeze in it either
could it be the water pump is knackered
or has the head gasket gone
the engine runs sweet apart from this problem
no oil in the water
no water in the oil
the rad cap is a 16 lb one

Dave

[Tank]

My XJ used to get very hot almost to boiling over if i did a long crawl when offroading but always fine when using normally.Did you try the thermostat to make sure its working properly and allowing water ok? Also it is possible you could have an airlock somewhere in the system as there is a specific way of refilling the system i believe. Just my thoughts,but i could be way of the mark. Im sure one of the more experienced XJ guys will confirm or condemn

[Davemate]

new stat fitted day after i done the rad
thinking that might be why the temp gauge never really went above 1/4
should have done it whilst the rad was out but i could not find the damn thing
(i must sort the shed out one day )
as for filling i was told by someone that the system
"will bleed itself on its own"
i do not hear any swishing sounds coming from the heater
when i an sitting in the jeep when i start it up or when it is running
bu that's not to say there is no air in the system
but there can't be much
if any

i have heard of a sniff test
is that a test for head gaskets

[Green Jeep]

i have heard of a sniff test
is that a test for head gaskets

It tests the water to see if there is any oil in it, simple test, most garages can do it.

Water pump are normally good for around 140,000.

Worth flushing the rad through with rad flush? Can't be a bad thing to do?

Cheers Maf

[Davemate]

i have heard of a sniff test
is that a test for head gaskets

It tests the water to see if there is any oil in it, simple test, most garages can do it.

Water pump are normally good for around 140,000.

Worth flushing the rad through with rad flush? Can't be a bad thing to do?

Cheers Maf

even though its a brand new rad!!!!
will a sniff test pick up if the head gasket is gone between
a cylinder and a water way
or will it only do the oil ?

[Mike Pavelin]

The test doesn't detect oil, it detects exhaust gases.

[Davemate]

so with no visable oil--water contamination
a snif test would tell me if the head gasket
has gone accros from cylinder to water way

[Davemate]

would a dodgy rad cap cause the syptoms
at the top of this thread?

i was wondering if the cap was releasing
at a too low peasure it would let the peasure
of the system push the water out into the exspantion bottle
or am i clutching as straws

[Dave69]

take the spark plugs out to see what condition they are in. if the head gasket has gone you will see one spark plug slightly wetter than the others or a definately differnt condition. If the jeep is running fine at idel with no coughs/splutters or being irratic i would then take the gues the head gasket might be ok. what you could do is run the engine with the rad cap off until it is warm and the thermostat open. by doing this it will allow and trapped air to bleed itself out of the cooling system. with the fan running all the time you should be ok. have a large jug of water/antifreeze mix to add when you loose some. as the air is bled through it will push coolant out of the cap so top it up when it stops and the level then drops.

[Davemate]

i will whip the plugs out tomorrow
and have a look

is there anyway to "test" a water pump
i read a post on here somewere
that someone changed their water pump(can't remember the reason why)
and the impellars had almost rusted away
as i have not had much-any antifreeze in my system for a while
is it a possibility my pump has done the same
or does that not happen

[sprintagogo]

Simple/cheap things first. I have seen many threads on Jeep forums where just changing the rad cap has cured random coolant loss so I think it is definitely worth a try in this case before you start looking at more serious issues. The rad cap is the only thing that limits the movement of the coolant from the cooling system to the header/overflow tank and the cap should have a specific opening pressure (around 12-18psi I think?) so if it is failing and opening at much lower pressures then you will see the excess coolant movement that you are experiencing.

Give it a try and let us know how you get on.

In relation to examining spark plugs for signs of head gasket failure, I believe any coolant getting into the cylinder causes the plug to appear very clean as it strips all carbon and residue from the plug tip?

[Davemate]

i have put a new rad cap on
and i went shopping (i had to the wife is at work and i am off sick so i had no choice
                               she threatened all sorts of things if i didn't go---honest!!!!)
when a got to the shops i watched the water rise a tiny bit ofter i had switched it off
but that was it
and the same thing when i got home
temp was where it should be
so after all of the above
it might (touch wood )have been a dodgy cap
i will check the plugs later anyway
but i am hoping that the system was just pumping it self clear of air

thanks for all your helpful ideas
i'll let you know !!!

[Davemate]

so far so good
looks like it might have just been the
rad cap 
the rad was knakered
but it looks like i may have refitted a dodgy rad cap
which came with the rad
refitted my old but good cap and like i have said
____seems ok!!!!

[loosenup]

Dave
an easy way to test water pump is to pinch one of the heater hoses that runs along the engine on the driver side , when you release the pipe you should be able to d=feel a surge throught the pipe, obviously not letting go of pipe completely .. if no surge.. then either there is no water in the pipes ( airlock) or pump is knackered.
it was my water pump that had no impeller left.. mind you , the jeep had done 156000 miles and engine was still sweet.
phill

[Davemate]

i will check that today
thanks

i am hoping my rad went pop as i had no antifreeze in the system
and it must have rusted out
new rad came with a cap and i am hoping it was that the cap was knackered
but if the rad has rusted out i want to make sure nothing else has!!!

so make sure you have anti-freeze in your system(lesson learned )

[Dave69]

the anti freeze while it stops the water from freezing it is also a rust and corrosion inhibitor

[Davemate]

yep
i did know but
its called being lazy
then
being skint as you have to replace engine bits

[bonza]

I reckon you had an air pocket.

these engines do have to be bled when ever they are drained of coolant.

best way is remove heater hose connection on the stat housing and fill until fluid pours out of the port, then connect the hose.

thenwith the rad cap off run engine until warm enough for stat to open and create a coolant flow into the top of the radiator header tank. squeeze top hose to purge out air trapped in the top of the radiator, topping off while this is being done. I know that whenever I have drained my coolant it always takes about three or four engine warm ups and cool downs before it is completely bled.

and having an orifice hole of 1.5mm dia in the stat flange helps as well.

[Davemate]

well it seems to be ok
i have checked the water level
after every trip
and it seems ok
i am going to clacton in a couple of weeks
so that will be the final test