Overheating problems

[Austin-Rover]

I have just brought my car back home from the garage where amongst other things, the radiator fan was fixed. Travelling down the Motorway, the car overheated again, but fortunatley, we managed to get home. The main reason the car went into the garage was to get the fan on the radiator fixed to avoid these problems. Does anyone have any ideas as to why it overheated again, especially on the motorway - i would have thought it had a good flow of air to the engine when going fast?

[Maria]

First, possibly stating the obvious, check: is it actually overheating? Does the engine feel warm, and/or do you get steam out of the bonnet. Never trust a Maestro temp gauge - they lie!

[Austin-Rover]

Well, apart from the flashing light on the dash, and the temp gauge being in the red, there was no steam coming from under the bonet, but there is still steam pouring from the coolant tank after i took the cap off, and its been 45 minutes since i got home, so it must have been hot.

Its all vey well saying that Maestro temp gauges can be inaccurate - but how do you know when to trust them and when not to?

[SimonR]

Could it be an airlock? - if the garage had to drain the cooling system then they may not have refilled it correctly. The usual way of testing for this is to see if the coolant level has dropped significantly, although yours will have done anyway if it's evaporating.

Another thing to do is when it's cooled right down again, take off the expansion tank cap and run the engine. The water should be static in the tank until the thermostat opens (i.e. the engine is at running temp) and then you should be able to see it move around in the tank. Obviously switch off the engine as soon as it starts. This should take no more than about 5 - 10 mins from cold.

It it's not moving around then it's not doing it's job!

You're right that it should not over-heat if it's on the motorway and going fairly fast, but if the coolant is not circulating through the radiator then it would not cool down. The same is true if there's loads of gunk in your cooling system. You could try back-flushing it with a hose pipe.

I don't know but could it be water pump related?

[Guest]

Does the fan actually comme on? My sensor recently packed up and caused overheating. Does it actually work, short out the terminals from the radiator sensor, may need the ignition on. If all this checks out OK then is there a blockage, try flushing as in the last reply and the airlock thing. If all is still OK then possible head gasket failure, Ive had this as well, a cylinder pressure test will decide this. If everything is OK then it's head scratching time.
Enjoy
John

[Austin-Rover]

The sensor is 'brand-new-out-of-the-box' stuff, so there should be no problems there. I dont think the head gasket would have gone as it has just come back from the garage and they have had a good mess with the engine, so if it had, they would have told me.

I will see what happens next time i take the car out.

On Monday morning, when we took the car in, it took a whole 4 miles for the temperature gauge to register anything, and on the way back today, it only started flashing when we were on the motorway...

[Guest]

Also forgot the thermostat, is it jammed shut?

[Maria]

Ah, if it's flashing on the motorway without showing any signs of steam or anything, I would be tempted to say that your fuel ECU might be on the blink. Happened to me a while ago - the temp gauge used to go up, flash, then drop back down again, then flash again etc etc. Tried all sorts, then swapped the fuel ECU and it was cured

[D87SMW]

ECU - it has a manual choke...

[Guest]

If i may, id like to place my bets on the fact that its a faulty thermostat... no matter how fast you go, a faulty thermostat will make the temp go red hot... If its an A series engine, be careful of the thermostatr bolts when replacing, they can snap off.

and now for the finale... "Waiter, there some soup in my flies!"

[Austin-Rover]

Right, I have had the engine running again - just on the driveway for about 20 mins (which is the same amount of time it was driven for this morning of the way back from the garage). The engine will warm up and the fan on the radiator comes on when required which means the temperature gauge is held constantly half way on the scale (with the indicating needle pointing straight down). It all seems to be working properly now - but it still doesnt explain why the temp gauge was flashing earlier....

Any thoughts...

[SimonR]

That wouldn't be Cockaleekie soup would it? :laugh:

Seriously, I'm inclined to agree with Topgear about the thermostat. Perhaps change it anyway...?

[Guest]

Frickin daft ECU's...I'm SO glad mine is in it's rightful place..filed in my bin.

After my crash it started being utterly random and played hell with the autochoke..it's because of the damned thing my engine now sounds quite ropey..

It used to do it's own twisted thing, and go up and down at will. warning lights and "Warning, high engine temperature" were normal.

Eventually with the help of the good people on the MGBBS and Maestro Web, I ditched the whole damned thing and went for a "normal" temperature sensor wired direct to the dash. I can't tell you how good it feels to not be guessing the engine temp after 2 years..

If you already have a manual choke, and you find the ECU in place..bypass it. Without an autochoke it has very little use..

As everyone else has said..if you're sure the fan sender is good, and the fan works..that should come on before the red light does..

If the light is on, but no fan..be doubtful.

[Guest]

As has already been mentioned, the red light is not a reliable indication of whether or not the engine is uncomfortably hot. On our K-Reg Clubman, it comes on before the fan does (and yes, the fan is working). It comes on at almost exactly half-scale on the temperature gauge. This is about where the fan came on on our Special (which, of course, didn't have a warning light). We're not quite sure whether to assume that the temperature gauge is the same as the old car or the fan, i.e., is the temperature gauge the same scale, or does the fan come on at the same temperature?
If we assume that the gauges are the same, the Clubman definitely heats up quicker than the Special. Is this anything to do with the cat.? If the fan trigger is in the same position then the red light comes on unnecessarily early. When we came back from Scotland, and were doing 70mph on the motorway for 8-9 hours virtually continuously and heavy laden (in the Special), the temp. gauge sat at just over half gauge the whole way, and the fan was on all this time.
All this would lead us to conclude that the gauge and warning light are just over-sensitive. However, we do seem to get water bubbling out of the pressure-cap from time to time, but this is usually after the fan has come on.
We're pretty much assuming it's fine; it doesn't seem to be doing any damage, and we're not doing anything differently to what we did with the same engine, etc., etc., in the Special, so if there's not something obviously malfunctioning, why should there be anything wrong?

Looking on the back of the instrument panel which was in the car before we swapped in one with a rev. counter from a scrapped Monty, my dad points out that there appear to be potentiometers, accessible from the rear of the panel, with which to adjust the threshold for the fuel and temperature warning lights. However, doing anything with them would require removal of the instrument panel, so we can't be bothered at the moment.

Hope this is of some help, sorry it's so long.

Peter

[E_T_V]

I had similar problems on our meastro for ages. Things to check are:

1. Blocked radiator - Feel with your hand if it is hot all the way down the radiator, ours was half blocked.
2. Thermostat. - Sounds like it isn't that though
3. Waterpump. - disconnect the top hose and crank the engine, water should be forced out at a reasonable rate.
4. Head gasket - Do a compression test to be sure.
5. Duff temperature sender. get a new one they are cheap.

Hope this helps

Dan