36 replies to this topic

[Paintmonkey]

Ok
My Clubman Estate was running fine until I decided to fit one of those extra engine steadies. Since I was having to undo the thermostat housing I thought I'd take the opportunity to fit a new thermostat and that's where my problems started!!
Ever since fitting the new thermostat, the temperature guage sits just under the red after about 3 or 4 minutes. Even turning on the additional electric fan makes no difference. Fuel guage works ok, so it's not the voltage stabiliser. Feeling the pipes in the bay, all the ones around engine and going to/from heater get hot, yet the water in the radiator is stone cold! Thinking I'd got a faulty thermostat, I fitted another new one and changed the temperature sender. Still the same problem. I removed the thermostat altogether and engine runs at normal temperature, no need for electric fanand the water in the radiator gets warm. Mentioned this at a friendly local garage who said the head gasket has gone!
Does this sound right or was I just unfortunate enough to get 2 faulty thermostats??
Any ideas on what else it could be?
Cheers
Rich

[newdawn1st]

Are you sure the new thermostats are the correct type? if the rad is cold then the thermostats not letting coolant thru, you said with it removed it runs at normal? i've had a head gasket go before and my engine red lined so cant see it being that plus your engine would be lumpy / stall / etc. check your oil to see if has water in it to, worth a check. I'm by no means all knowledgeable about this but i'd say it isn't as severe as a head gasket. have you put your old thermostat back in see how it runs then?

[Paintmonkey]

Are you sure the new thermostats are the correct type? if the rad is cold then the thermostats not letting coolant thru, you said with it removed it runs at normal? i've had a head gasket go before and my engine red lined so cant see it being that plus your engine would be lumpy / stall / etc. check your oil to see if has water in it to, worth a check. I'm by no means all knowledgeable about this but i'd say it isn't as severe as a head gasket. have you put your old thermostat back in see how it runs then?

Being the tidy person I am, I threw away the old thermostat!!
Engine runs fine with or without the thermostat apart the temperature thing!!
Thermostats were purchased from a garage that specialises in minis and who know the set up of my estate (its got a 1275 engine fitted from a 1993 mini rio.
No sign of oil in the water.

[mars red mike]

The thermostat lets cooled water out of the rad not hot water into it. I would say that changing the thermostat has shown up a problem elsewhere in the cooling system. I would say that it sounds like a silted up radiator. With the thermostat in it restricts the coolant flow so the hot water isnt being cooled by the rad hence the temp goes through the roof. Remove the therostat and the restriction in the system is gone, allowing a bit moe coolant to be pumped around.

[mars red mike]

Are you using the thermostat and sandwich plate or just the thermostat housing on its own. If you are using the sandwich plate the 'stat must go in the plate and not in the head. Although that shouldny cause the problems you describe it may contribute to it

[newdawn1st]

The garage you said told you its the head gasket, is this the mini one? if it is that a compression test should give you more of an idea, noticed any coolant or oil bubbling out thru the gasket around the head? bit out of my scope now really, dont want to start guessing too much tried searching the forum for something similar? head gasket or thermostat?

Edited by newdawn1st, 05 May 2009 - 11:34 AM.

[Paintmonkey]

The thermostat lets cooled water out of the rad not hot water into it. I would say that changing the thermostat has shown up a problem elsewhere in the cooling system. I would say that it sounds like a silted up radiator. With the thermostat in it restricts the coolant flow so the hot water isnt being cooled by the rad hence the temp goes through the roof. Remove the therostat and the restriction in the system is gone, allowing a bit moe coolant to be pumped around.

Could be. I like that idea a lot more than the head gasket!!
Only thing is the car was only put back together just before Xmas and hasn't done many miles since. The radiator was flushed out before I put it back onto the car.
If it was a semi blocked rad wouldn't that have shown up with the old thermostat in?
Only got problem when I fitted the new thermostat, before that (with old thermostat in) temp gauge would get up to normal mark and only go over this if I was sat in traffic or had left it ticking over for ages while I did something else. The temperature would drop when the electric fan was switched on.

[Paintmonkey]

Are you using the thermostat and sandwich plate or just the thermostat housing on its own. If you are using the sandwich plate the 'stat must go in the plate and not in the head. Although that shouldny cause the problems you describe it may contribute to it

Thermostat housing on its own.

[Paintmonkey]

The garage you said told you its the head gasket, is this the mini one? if it is that a compression test should give you more of an idea, noticed any coolant or oil bubbling out thru the gasket around the head? bit out of my scope now really, dont want to start guessing too much tried searching the forum for something similar? head gasket or thermostat?

Yeah it's the mini garage that said it's the head gasket!
I haven't noticed any coolant or oil bubbling around head.
Oil & water levels aren't dropping.
Had a look at the FAQ section on engines and cooling but couldn't find anything that answered my query!

[brianmini]

The thermostat lets cooled water out of the rad not hot water into it. I would say that changing the thermostat has shown up a problem elsewhere in the cooling system. I would say that it sounds like a silted up radiator. With the thermostat in it restricts the coolant flow so the hot water isnt being cooled by the rad hence the temp goes through the roof. Remove the therostat and the restriction in the system is gone, allowing a bit moe coolant to be pumped around.

Are you sure? I thought the whole purpose of the thermostat being closed was to let the engine (and the water within) warm quickly, thermostat opens letting the now hot water percolate down through the radiator to cool before being pumped back around the engine..

I changed my radiator a few years back and had a similar problem to you, it was an airlock in the system. Have you made sure you've let all the air out the system? Take rad cap off when cold (also put the heater to the hot position), start the engine. After a short time you should hear gurgling and the water level in the radiator will drop (if you have an airlock) then top up with antifreeze. Turn engine off when the coolant has settled and stopped gurgling away. Let the engine cool and then re-fit the rad cap. Job done.

[mars red mike]

I cant fathom out why the heater outlet red hot which is dumped into the bottom hose and into the bottom of the rad, but the water in the rad is cold. Did you blees the air out of the system when you fitted the new stat?

[newdawn1st]

this was my thinking too brian, the thermostat only got opened when your engine was getting past normal temp and needed to employ the rad to start cooling.

still can't make any more suggestions to the orignal problem tho

[mars red mike]

Ooops ive made a booboo here. Sorry Brian you are right I had got all fuddled up. I hang my head in shame

[il-barba]

do you have a bypass hose? if not you need to drill a few small holes in the thermostat itself so that it can function well. also fitting upside down will not work well i think

[Nightrain]

As above no bypass circuit means it's using the heater as a bypass, hence your heater/heater pipes getting hot. You need to either refit the sandwich plate or drill the thermostat. If you drill the thermostat the system will not work that effectively, you'll have a crab heater when it's cold and the engine will take longer to warm up.