Overheating... but not the radiator?

Post by **badfelafel** » Fri Sep 15, 2006 3:55 pm

OK Now that the radiator is out, did a wee experiment - just ran some water in the top of the old one, thinking nothing would happen. Very quickly, it came back out the bottom (a bit browner) but freely and quickly.

That makes me think that the cooling system problem lies somewhere else...

Can't find a hose to flush through the system.

Whats next to try though - the water pump?

Am i right in guessing that my 2 remaining options are:

-water pump not pumping or
-tubes and pipes and places water goes blocked up

Could it be anything else???

Many thanks, all!

Post by **alex_holden** » Fri Sep 15, 2006 4:07 pm

The thermostat could be stuck in the closed position.

Post by **badfelafel** » Fri Sep 15, 2006 4:10 pm

thx - have a new one and a gasket, will have a go!

Post by **badfelafel** » Fri Sep 15, 2006 4:35 pm

Great call! Replaced the thermostat. Old one is in a bowl of boiling water and has opened only ever so slightly. How much should it open? I wish I had boiled the new one to see before I fitted it!

While I had the thermostat off, poured a big jug of water in the big hole at the top of the engine. Where the oil normally goes... ONLY JOKING! Where the thermostat goes. It came out at the bottom and looked quite clear.

So now the question is, should I replace the water pump!

Think it can be done without dismantling the front of the car, just using the space where the radiator was????

:) Thanks again!

Post by **RogerRust** » Fri Sep 15, 2006 7:18 pm

plenty of room!! you can do it with the radiator in if you try hard. If you are worried about the water pump change it and the bypass hose while its easy to get to. Personally I'd put it back together now and give it a try. All said and done it wont take long to whip the rad out a second time.

I wouldn't put any antifreeze in yet - wait untill your happy then drain some water out and add the antifreeze then.

Post by **bmcecosse** » Fri Sep 15, 2006 10:26 pm

Water pumps very rarely fail - usually only if run 'dry'. If the stat was stuck - then there's the problem - don't worry about pump. Give the rad a good flushing and stick it back on. Check condition of hoses and bypass hose (NOT the daft wee convoluted type I hope) and the fan belt while in there.

Post by **badfelafel** » Fri Sep 15, 2006 10:53 pm

i've got a shiny new water pump in a box - wondering if i may as well stick it on?

q for that one is afterwards, tightening the fan belt back up - how tight! ??????

thx all

Post by **minor_hickup** » Fri Sep 15, 2006 11:24 pm

So you can turn the fan without the belt moving, but not the alternator. In other words not too tight!

Post by **alex_holden** » Thu Sep 21, 2006 12:00 pm

I've just got a new 88C thermostat, so I decided to do a bit of testing. It appeared to start cracking open at 90C according to the thermometer, then I got called away from the stove before it had fully opened and by the time I got back the water was boiling and the thermostat had opened by slightly less than 8mm. I then let it cool down slowly, and it reached the fully closed position at 86C. It wasn't a quick on/off - there's quite a few degrees temperature difference between fully open and fully closed, and there seems to be a few degrees hysteresis too.

Post by **bmcecosse** » Thu Sep 21, 2006 1:21 pm

Aye - boiling it up in a pan is the way to do it. 88 is ideal for a winter stat!

Post by **les** » Thu Sep 21, 2006 10:22 pm

Very quickly, it came back out the bottom (a bit browner) but freely and quickly.

Don't discount the rad, the water may run straight through but not via any blocked tubes!

Post by **Axolotl** » Sun Sep 24, 2006 4:02 pm

I've just been through a similar rigmarole with my 1098cc traveller.

It was o.k. up to 50 mph, but anything over that and the temperature gauge steadily rose up to the red area (boiling plus some). Cooled down as soon as I opened the heater water valve, but went back up when I closed it. Not too comfortable in the recent hot weather.

I went through the usual flushing, back flushing, used Radflush, made sure timing and fuel mix were spot on, checked for binding brakes, slipping fan belt, even changed the (short vane) water pump for the correct long vane type, and it still overheated.

Water appeared to pour through the radiator quite happily when flushing it out, but as a last resort, I have fitted a reconditioned radiator, and the problem is solved. The temperature gauge goes up to about 180 degrees F and stays there, no matter what. (Just like a real car).

As Les says, if some of the tubes are blocked, water will still run through the others, but the cooling effect of the radiator fins on all the tubes will be lost.

Don't discount the radiator, especially if you've tried everything else and it is still to hot.

Post by **bmcecosse** » Sun Sep 24, 2006 4:08 pm

So - is it still overheating ?

Post by **Axolotl** » Sun Sep 24, 2006 5:57 pm

Badfelafel's or mine?

Post by **bmcecosse** » Sun Sep 24, 2006 6:03 pm

Well - either really !! But the Q was aimed at Barry.

Post by **minor_hickup** » Sun Sep 24, 2006 9:29 pm

axolotl wrote: went through the usual flushing, back flushing, used Radflush, made sure timing and fuel mix were spot on, checked for binding brakes, slipping fan belt, even changed the (short vane) water pump for the correct long vane type, and it still overheated.

Water appeared to pour through the radiator quite happily when flushing it out, but as a last resort, I have fitted a reconditioned radiator, and the problem is solved. The temperature gauge goes up to about 180 degrees F and stays there, no matter what. (Just like a real car).

I had the same thing happen to me. But the repeated attempts at flushing and cleaning meant I have a fantasticly efficient cooling system and a brilliant heater.

Post by **Axolotl** » Sun Sep 24, 2006 11:14 pm

Mine's cured. New water pump slowed the temperature rise down but didn't stop it, new radiator has stopped any rise above the thermostat opening point.

Post by **badfelafel** » Sun Sep 24, 2006 11:43 pm

I don't think so, but it might be! It ran OK into town, but when in traffic the gauge read near hot, while it felt and smelt ok there was a lot of hot air coming through the heater inside! Might be ok... but might not!

Is there any other good way of telling how hot the engine is running????

Post by **Packedup** » Mon Sep 25, 2006 12:41 am

Use the temp gauge, Luke...

Sorry, random film quotes going through my head.

Anyway, if it's running hot when not moving (or moving slowly), then the cooling system is marginal for some reason. Lack of fan would cause those symptoms, as would missing rad fins, blocked rad fins (as in the outside of the rad is blocked), obstruction between rad and airflow...

But could be anything else too given the amount of cool air flowing through the rad will be higher at speed, so even a pathetic trickle of water through it will be cooled better. So stat, pump, hoses etc. If you haven't already, then fit a new pump - The old ones have cast impellors that should last forever, but by the time you've removed it to check it's not caked in crud you may as well fit a new one. Same goes for the bypass hose (or do yourself a favour, fit a Metro pump and block the bypass hole in the head). Pop the top and bottom hoses off, make sure they're clear and not collapsing*, and flush the block through.

* - I remember one car I had where the top hose would collapse and block itself for no apparent reason. Fitted a new hose and all was good again

Post by **bmcecosse** » Mon Sep 25, 2006 5:44 pm

Certainly agree about the bypass hose - it took BMC/Rover many many years to realise this thing was totally unecessary! Think of all the cost/time lost/distress that wretched by-pass hose must have cost over the years !!