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OK,
My M38; once in a Blue Moon blows all its water out of the radiator.
The first time it did this was last October, just after I'd added the antifreeze.

The second time was about an hour ago.

Between the two shes done a couple of hundered miles on longish and short runs with absollutly no bother.

This phenomerna happens shortly after I've started her once she reaches opperating temp. ie start her up, let her warm up, leave home and about a mile down the road 'WHOOSH'

The radiator has been reconditioned and has no problems, the thermostat is in the right way up, the engine never over heats even in the hottest weather in very slow/ standing traffic, since rebuild its been all over Europe without a hitch.

Once up to operating temp the gauge pretty much stays in the same spot, you can just say notice some movement when the thermostat opens.
Thankfully I've been left with enough water each time to just limp home.
Any ideas greatfully recieved,
Thanks,
Dave.

Have you checked the radiator cap?Is it blowing out of the cap,or somewhere else?
A bad cap can give way after enough pressure has built up occasionally.

Thanks for the reply,
the cap is brand new and rated I think (the jeeps away for the night now) at 7lbs. The neck ring passed pressure test with the test cap at the rad shop when they pressurised the rad.
Its hard to say if its blasting out the exansion pipe and spraying everywhere due to the fan or coming past the seal in the cap.

It certainly empties the radiator FAST, ie from the first sniff of steam to stopping at the side of the road, the radiator is almost empty. This makes me think the expaasion pipe simply can't cope and the steam and water then exits via the filler neck.

If it did it more than twice a year it would be easier to trace.
As a temp measure I might do what the French did with their jeeps, that is; mount a half (wine, vin in French) jerry can in a tray where the winch would normally sit and run a flexy hose from the expansion pipe through a pipe in the jerry can cap into the jerry can.
Mind , if it's blasting past the cap that won't help.
Thanks,
Dave

Dave,

Are you sure that there are no air pockets in your system.

If you are losing that much water it must be blowing off a lot of steam.

Maybe the engine water jackets have some partial blockages that would make it appear that you have filled the coolant system.

Just a couple of thoughts.

Sounds like an air pocket or a thermostat problem. Have you checked the thermostat? Even if its brand new doesnt mean its working properly. I think one way you could see if your filling it all the way is to measure the amount of fluid you putting in the system. I know some where in the TM manuals it list the capacity of the system

When I added the antifreeze in October 2005 drained the engine down by the taps and removed and replaced the bottom hose. I pre-mixed the quantities to the TM in a bucket and then added it. Started the the engine after a coulpe of pints had gone in and it took the lot, filled it up nicely when hot to just about the bottom of the baffle in the top header tank. I might have split as much oa a cup full at absolute max.

Ran great ticking over and at raised revs on the drive. Took it for a spin and it blew all the water out about a mile later.

I then repeated the filling process outlined before and its been great all over the winter till yeasterday when it did the same thing again.

When I had the head off and it got the new bearings and valves and springs the one thing I didn't do was punch out and replace the core plugs. I did flush the engine, several times with several 'flushing agents' but I didn't actually look behind those core plugs. Lesson for next time.

Given the almost EXPLOSIVE nature of this problem when it happens I'm tempted to think the water is traped in the block and is then suddenly released to the radiator.
So as you say even though the thermostat is new there could be a problem there???????????
I'm simply puzzeled by it.
On a lesser note the price of anti freez went through the roof this year and its proving expensive!!!

Now, my jeep dealer can send me a thermostat in a couple of days but if I had a number my parts shop will have one on the shelf.
Anybody got a number I can use at my loacl store???
Thanks,
Dave

I would agree that an air bubble is the first thing to check.

Sometimes a system needs to be "burped" after refilling. And ensure the thermostat bypass allows at least some slight circulation even when thermost is closed...helps to ensure the thermostat gets warmed properly, and passes air bubbles.

Also, I would suggest you run a cylinder compression check, and or use a sniffer to test the radiator for exhaust gases. Possibly a head gaskest problem? Sometimes compression leaks show up only under load or after hard running.

Good luck!

Pete

Dave here are the numbers out of ORD 8 SNL G-740.

WO-646812, Ord part # 7348571,Thermostat,water temp(issue until stock is depleted,then use Thermostat,2930-530-7509-G179)

Ord Part # 5307509, (Use only after stock of thermostat,2930-734-8571-G-740 is exhausted)

Dave,
Is the new botton hose have the spring in it?
Remi

Very good point, no it doesn't....... but all my other Mseries do; what do you think could be happening?? I vaiguely remember this from some other place, something about the hose collapsing under suction??
Thanks,
Dave

Dave,

I remembering hearing about that too, Remi makes a good point.

I think that was on the G503 a year ago.

Might be worth checking out.

Obviously I'm doing something wrong with the G503 search engine. I get loads leads but not one mentions the bottom hose spring,
I'll try again later,
Thanks,
dave