losing coolant

[ennisboyne]

noticed leaking crankcase seal and radiator warning light coming on quiet often. (1997 E 200 Class 180,000 miles)
Mechanic fixed crankcase seal but radiator continued to lose water. He tested it for overheating but couldnt find fault. Said he didnt want to do anything till I found where the leak was coming from.
I am now satisfied it is not leaking coolant, but is blowing it out the escape tube just under the radiator cap,leaving a rust coloured residue
If I fill it to well over the mark and just below the raidiator outflow pipe, It will drive for 100 miles without the radiator warning light coming on. I then refill it after it cools with 1 and a half litres of water.
My mechanic thinks I am imagining this. I feel isolated that the car of my dreams is about to blow up and no-one believes me.
Any advice:-(
Paul

 

[dave.robbo]

Is the temperature needle acting normally?
I think one of the first things I'd do is put a new rad cap on. The springs DO wear, and so it may be lifting too early, and therefore 'leaking' water out of the escape tube.

 

[Uncle Benz]

Agree with the rad cap thing, but get a 'block' test done too. Sometimes called a litmus test, it checks for exhaust gasses in the coolant and tests for a head gasket failure. A head gasket problem will pressurise the cooling system more than normal, and often lift the rad cap allowing coolant to escape.

 

[television]

As Uncle Benz, head gasket leak blowing up the system,,you could leave the rad cap loose to test,just on a touch

 

[dave.robbo]

you could leave the rad cap loose to test,just on a touch

I'd say it would be safer to leave the cap off altogether. You'll see the level rise fairly quickly if the head gasket's gone. I had this on my LandCruiser earlier this year.

 

[television]

I'd say it would be safer to leave the cap off altogether. You'll see the level rise fairly quickly if the head gasket's gone. I had this on my LandCruiser earlier this year.

Sure and I go along with that

 

[ennisboyne]

Thanks, Guys. I will start by trying a new rad cap, if that fails then drive without rad cap

 

[dave.robbo]

Nooo! Don't drive with no cap! It WILL boil over!!

Run the engine with no rad cap, from cold, and watch the level rise in the rad. Don't actually drive!!

 

[keith100]

The OP said coolant blows out of the escape tube and he can see rusty residue from the outlet. Isn't that overflow tube supposed to be connected to an expansion bottle, so the coolant can be caught and sucked back into the rad as it cools?

Maybe the tube to the epxn. bottle is missing?

Or maybe the "escape" tube is something totally different?

 

[wireman]

The residue is not rust.

It is what happens when hot gas is infused into antifreeze, some component of the coolant turns into slimy sludge which if not treated will settle in the low water flow parts of the cooling system and set. Your radiator and heater are favorite hiding places for the sludge, some of the small tubes will eventualy get blocked if it does settle there. Once its settled there is little alternative (other than bodge and hope) to replacing the rad or heater matrix, flush it with a proprietary cooling system cleaner of the multi chemical type (a good one is old fashioned two chemical rad flush).

Most likely the head gasket has failed.

If the gas to water leak is small you wont see much happen maybe a few bubles will pass from the coolant to atmosphere in the header tank (cap off), if its big there will be a fountain to cope with especialy when you rev it up. Fill the header tank to brimming and look for bubbles, it may only do it once the engine is hot. The "litmus" test is a good idea, and it should be quite ok to run without a cap to test it, it won't boil up unless the engine gets over 100C (this sort of temperature would indicate even more firmly that your CHG is shot at), very slight evaporative loss will occur though.

Take great care when rooting about under the bonnet with the engine running, there is a big fan there and you might forget about it whilst moving away from some very hot water.

Dud water pumps often go unnoticed when water leaks from them, they usualy begin to leak only when hot and the coolant dries up instantly leaving no trace of the leak. Check for dampness or drips behind the pulley when its cooled off over night.

Whatever you find sort it out pronto, leaving it in a partialy OK state will expose your engine to the risk of suddenly running with no cooling.