MG ZR K-Series Overheating-Go on,say it!

[155V6]

My Express has started behaving strangely.On the way to work,(about 8 miles)it was fine for about the 1st half of the journey,heater working & temp gauge just below half.Then the heater got cold & the gauge went up to about 3/4,but not any higher.I carried on,keeping an eye on the gauge & it went back to normal.As I got to work,I could hear the expansion tank bubbling but the gauge was still pretty normal.I had a quick look & the level in the tank was up above the maximum & some coolant had blown out of the top.I also noticed the bottom hose was cold.

 I checked at lunchtime,the level had gone back down so I topped it up & ran it down the road.It seemed ok but the bottom hose was still cold.Not much else I could do,so drove home after work & it was fine.There doesn't seem to be any mixture of oil & coolant & the fan works when it gets hot.

I'm kind of expecting the worst,but hoping it could be something like the thermostat stuck shut,any thoughts?

[Peter C]

OMGHGF

 

Happy now?

[mrbenn]

Isn't there some sort of Saab valve that causes problems like this? IIRC Bollox had similar issues on one of his projects.

[Parky]

Probably just the sender.....these engines aren't known for this sort of thing

[Sloth in a bowl]

If bottom hose is cool then I would expect one of two things:

Water pump fail

Thermostat not opening

 

anything other obvious reason for coolant not circulating?

[wuvvum]

Airlock?  These things are prone to them, especially if they've been run low on coolant and then refilled without allowing the system to bleed.  My 200 VI did something similar once (temp gauge normal but chucking coolant out of the tank), and I'm pretty sure that hasn't got HGF - it was about 6 months ago it did that and it's not done owt similar since.

[purplebargeken]

2nd for pump or thermostat.

[HH-R]

The gauges are so heavily damped on these to be almost useless. Once they rise, Bad Things have usually happened.

[155V6]

I'm going to try the thermostat 1st,& get a new cap for the expansion tank too.If it's not that,I'll get someone who knows what they're doing to have a look 

[Station]

It'll be an airlock possibly. If it blows cold ever, that's what it is.

Open those bleed valves on the radiator (front right) and on the metal pipe under the distributor. Wear gloves when you do that as you will electrocute yourself.

I think there's a bit of hose jiggery that upsets water flow on the k-series, worse still on the MGF.

 

Would having a better water pump improve this I wonder?

[michael1703]

Run it with the top hose jubilee clip loose and slip a pick or thin screwdriver between the top hose and the radiator elbow and see if you can get any steam/air out.

[aldo135]

I had similar with my ZS 120 and it was the water pump