Coolant filling & bleeding...........HELP

[Sean.Smith1]

I drove my wedge rather hard yesterday for about 10 miles or so.........the temp gauge read on the 80 mark constantly (once warm of course), then I hit the town centre traffic...........now she's getting hot !!!

The old girl got very hot readimng alm,ost 100 on the gauge, but the fan didn't kick in. I parked up & she spued coolany into the overflow tank. I shorted the temp switch so that the fan stayed on permanently, let her cool down, topped her up & took her home for the night.

I have been thinking asbout it & I am hoping that she was air-locked in the cooling system, in such there was no water in the top hose (where my temp switch is - same as the Grif), I now need to know how to bleed the cooling system properly as I'm going to flush her over the weekend & take her out for another blast once the coolant has been renewed.

Can anyone help me ????

[cuneus]

Park uphill (or raise the front) and bleed from the cap on the hose from rad to engine. Start engine and keep bleeding till warm

[GreenV8S]

Not convinced by the air lock theory. If you have any water circulation at all that otter switch will get a pretty good reading, and without water circulation it will overheat within minutes. Far more likely IMO that the otter switch itself has failed.

[streaky]

Fit an override switch so you can operate the fan(s) regardless. My 390SE was modifed during its sojourn at the factory and has no otter switch; the fan is operated exclusively by the driver (I think it's supposed to work off the ECU ... but it doesn't). I find it very useful, in that when exiting a motorway after a blast (not the M4 obviously ) to traffic signals on the roundabout or if I see a hold up ahead, I can switch the fan on early.

A warning LED would show that an otter switch activated fan was on - which can be a comfort.

When pressing on, my temperature gauge sits at 85, then occasionally rises slowly to ~100 before falling quickly (no fan) to 85. It's done it for the past few years, and no-one knows why .

Streaky

[jmorgan]

Second the overide switch and what Dave says.

Probably no help but I had a an awful time with a heater airlock so fitted a bleed valve where the pipes passed through the bulkhead but its a 400 and the heater pipes are quite high up. Helps me a lot in filling the system and checking for locks.

[GreenV8S]

streaky said:

When pressing on, my temperature gauge sits at 85, then occasionally rises slowly to ~100 before falling quickly (no fan) to 85. It's done it for the past few years, and no-one knows why .

Could be that the stat is sticking closed, or being held closed by water pressure (can be an issue if the bypass is restricted). You could use a thermometer to confirm whether the engine temperature is actually changing that much, and measure the top hose temperature to show whether the stat is opening suddenly when the temperature drops.

[jmorgan]

Out of curiosity, I have bought a few stick on temp tell tales. Assuming the best places are top hose to rad and bottom hose out on the metal parts? I know they are not calibrated but a good idea as to what is going on. They are max temp tellers only. That is show the max reached at any time and if a higher one reached they show that, they do not appear to go down with temp.

Already have core plug ones on.

[GreenV8S]

If you want to measure the peak temperature, put it somewhere in good contact with the water and away from any sources of heat soak. The radiator end tank would be a good spot. Make sure it's on metal not rubber.

[jmorgan]

Ta. Will do.

[ferlin]

Sean.Smith1 said:

I now need to know how to bleed the cooling system properly as I'm going to flush her over the weekend & take her out for another blast once the coolant has been renewed. Can anyone help me ????

When I flushed my system out and refilled with fresh antifreeze solution I had the heater lever turned on hot and filled it through the top hose filler cap with the engine running.The final topping up was done via the expansion bottle but only once the water level was upto the top of the filler cap tube.I never had any problems although it took a while to fill up and get upto temperature and the engine now runs at about 85 degrees.

[briantvr350]

Hi guys...

been there many times over the last 8 years.

Believe me, the only way to fill the cooling system is as described in the bible... basically fill the system from the swan neck. leave the cap off, start engine and allow to warm up... topping up as required initially... replace cap on swan neck once you are sure stat is fully open.. Then replace cap... (have a read of the relavent page before you start, above is from memory)

You should be able to let the car idle watching the temperature gauge and observing when the fan cuts in and out...

Car may blow out excess coolant once you switch off the engine. If this continues beyond the first couple of warm up and cool off cycles then it's a good bet there's still air in there somewhere.

Regards,

Brian (and a Red 350i)

[Sean.Smith1]

THANKS GUYS - car's now sorted !

I've fitted 'tell tales' all over her (well not ALL over) & I've also fitted a by-pass switch for the fan to the OTTER switch on the top hose.

Went out for a proper blast over the weekend - who needs alcohol ?

[jmorgan]

Take it the otters not in the rad side tank then?

[Sean.Smith1]

no - the otter's on the top metal hose adjacent to the filler - thiswas a mod carried out by the previous owner & is the same as the Grif set-up.

[jmorgan]

Sort of went down that route as well, sealed up the rad and fitted an in line. Kept the overide wiring fron the old otter.