13 replies to this topic

[topcat]

Ive had my 1991 mini cooper (carb) for a year and a half now, when i first bought it in the summer i found out it had a slight cooling issue. I replaced the water pump, radiator, heater matrix and thermostat which helped but it still went about 3/4 up the temp gauge on a hot summer day when on the motorway. It never gets hot whilst in traffic, or racing through lanes, just on the motorway. Last summer i spent most of the time on the motorway with the heater on and windows down just to keep it cool. Now the weather has become cold, it doesnt seem to warm up! I drive half an hour to work and it doesnt get any where near normal temp! I went to change the thermostat again last night cause I thought it might have been stuck half open but it was fine. Tested it in a saucepan and it opened and closed. I think its 88 degree. I had a new one to put in but totally forgot so now I dont have a thermostat at all! Cold drive in this morning! need new gaskets now to put the thermostat back in. Anyone have any ideas on what the problem is?

[Jammy]

Have you tired changing the water temp sendor just below the thermostat, I wouldn't say its a common thing to go wrong, but it does have a fair bit. Always replace the simplest things first!

[topcat]

No i havent, I could try that, dont think it is to blame though because when it is getting too hot, it really is boiling over if you take the rad cap off. And when it says its cold, you get no heat through the heater. The sender only controls the gauge doesnt it?

[topcat]

by the way, I had to change the pump, rad, and matrix because they were all leaking anyway.

[Guess-Works.com]

Sounds like you need to flush the system.. but as jammy says, I suspect the guage and sender...

Does this have a leccy fan ?

Is that working..

Also could be that you're running lean and this is causing you to 'get hot' when cruising..

[topcat]

got an electric aux fan, smaller than the SPI

[topcat]

.........Sorry, as i was saying.......

got an electric aux fan, smaller than the SPI aux fan. This was not cutting in so i put it on a separate switch. I didnt seem to do much on the morotorway. I think its more for when you are in slow moving traffic isnt it?

If its that i'm running lean how does it explain why it doesnt get hot on a cold day?

My last mini was a SPI which always warmed up quickly to the normal mark on the gauge, then stayed there whatever the weather. With the cooper I have now, its usually too cold. Even in summer it runs cold untill i get on the motorway. I can understand why it overheats but surely if the thermostat is doing its job and stays closed until near the normal operating temp it should never run too cold?

[Cookie Monster]

I would get the thermostat back in quick as you can do damage by running a mini with out one, or a special sleeve to replace it. Also that would be why it didn't heat up too well this morning.

As for the sender unit, my lads used to read 3/4 plus all the time and even went over the red sometimes, but never boiled over. Changed stat, rad flush and coolant change didn't do anything. Changed the sender now never even gets to half.

[topcat]

but surely if its not even getting to half, its running too cold! Thats not good for the engine

[Jammy]

Thats IF its running cold, change the sender and see what happens! Also, as Cookie Monster said, if your running without a stat its going to take a while to warm up and you need to use a blanking sleeve in place of the stat.

[Dan]

This is why a C-N-H (cold-normal-hot) type electrical temperature gauge is almost useless. There is only one calibration of temperature gauge that's ever been fitted, but there have been five different thermostats for different engines and different territories three of which remain freely available. Most Mini's (especially 998s) will run slightly cool by the gauge all the time under most conditions. About 3/8 of the way around the gauge (and so just below N) would be what I would call normal for a 998.

Sounds like your car is fine except when cruising on the motorway, which points more to a tuning issue than a cooling issue as Guessworks said, either fuel or ignition. Haven't fitted a K&N filter by any chance have you?

Running slightly cool will develop more power (at the expense of fuel efficiency) anyway which is why most people change their thermostat and it certainly isn't bad for the engine so long as it is tuned to run at that temperature.

It is however very very bad for a Mini to run without a stat or a blanking sleeve as suggested above. What this actually does is allow the coolant to run diectly from the pump to the stat, straight up. It means that cyl 1 is very cool (as you noted, the sender is in this region of the head and so it sees cool water) while cyl 4 is stupidly hot as the water in that end of the engine is sitting stagnant and not flowing.

[ianbunyan]

Do as the mini doc say... he knows his stuff!

[topcat]

OK so plan of action is to flush through the whole system, put new thermostat in, and new sender and i also have new dials with gauge so i'll see what happens then. I'll have to wait for the summer to see if it overheats! Thanks for your help

[topcat]

oh and check timing \ mixture