staying cool

[davehaynes]

ive got a mk2 J reg 1.2 merit, carb model.
i fitted a new water pump 2 days ago as the old one was knackered and leaking. took it out today and noticed after about half an hour it still hadnt warmed up, still in the blue zone one the dash. after a further 3 hours it still hadn't moved so i thought it may be a faulty temp. sender.
i then gave it some welly round some country lanes and after some fast driving it started moving up to 1/4, but then dropped back down
anyone got any suggestions? carb set up wrong?
also, running cold, will this use more petrol?
cheers.

[meritlover]

sounds like the thermostat is missing or jammed wide open.

if its running as cold as that its likely causing excess wear to the engine, howerever. if it runs fine off choke, its unlikely to be using anymore fuel. but it requires further investigation.
im assuming the cooling system was properly bled following the pump change?

[davehaynes]

yep runs fine off choke, ill have to pop it in a garage if nobody has any suggestions.
i didn't bleed it, if it had an airlock it would overheat wouldn't it not stay cool?

[meritlover]

ive just given you 2 suggestions?!

yes it would show cool if not bled correctly, but because the sensor is at the top and back of the manifold, the engine might be melting whilst the sensor dipping into thin-air...

whip the thermostat housing off and check it. its not a big job

[davehaynes]

ahh i see ill have a look tomorrow cheers mate

[AlexW]

whip the thermostat housing off and check it. its not a big job

While its not for that engine but Spi's are harder to change thr thermostat as the rear cam belt cover gets in the way! Hence why i change the thermostat everytime i do anything to an engine, Only a couple of quid too.

[rysmee]

why would it be causing excess wear to the engine? surely the cooler the water the more efficient it will be in removing heat from the block as its designed to do? As long as the oil is up to desired temp of course...

[rysmee]

the only reason i say that is becuase i dont run a stat at all, the temp guage barely moves unless in traffic, yet the oil warms up nicely - even with an oil cooler.

[edens-xe]

the only reason i say that is becuase i dont run a stat at all, the temp guage barely moves unless in traffic, yet the oil warms up nicely - even with an oil cooler.
the thermostat is there for a reason! its designed to help warm the car up quickly to optimum temperature for better running, and then regulate the desired temp for optimum performance, fuel consumption and less engine wear!
removing this will make the engine suffer in the long run as your car WILL be using more fuel.
using excess fuel all the time is not good for the engine and cause 'bore wash' which will kill piston rings eventually and give you loads of trouble.

even cool running stats arnt really needed unless your running a say a c20let in a nova where high temp issues can be quite a common problem.

even fitting an oil cooler can cause harm if it didnt have one to start with,unless of course your running a tuned engine, or using the car for the track

[davehaynes]

what do people suggest then?
try a new thermostat?

[rysmee]

if it were me i'd undo the temp sender in the top of the manifold to bleed out any excess air. basically have the engine running and slowly unscrew it untill water starts to flow out (carefull if its warm/hot!) then you know that all the air is out. However - i used a proffesional coolant refiller on mine on many occasions and the temp guage still flew around with a mind of its own so it wont necessarily fix it.
Although as long as all the hoses getting warm - i.e the top hose on the left hand side to the top of the rad, the bottom hose and the return hose back to expansion tank (and you getting warm air to the vents in the car)(remember the centre vents tend not to get warm air) then it should be ok and personally i'd leave it. No point messing with the stat unless you got a real reason to suspect it (rad hoses not getting warm).

edens-xe - i see what you saying but with the spec i'm running the engine ran very hot with a stat in. its mostly track/'fast road' use so i doubt it ever gets a chance to run too cool. Even with an oil cooler i'm still seeing temps of 100 degrees when pushing it so i'm fairly confident its warm enough!

[edens-xe]

edens-xe - i see what you saying but with the spec i'm running the engine ran very hot with a stat in. its mostly track/'fast road' use so i doubt it ever gets a chance to run too cool. Even with an oil cooler i'm still seeing temps of 100 degrees when pushing it so i'm fairly confident its warm enough![/quote]

well thats understandable if ur running a tuned engine, but for a little 1.2 merit, performance isnt going to be mind warping so running a stat is the safest bet:thumb:

[rysmee]

agree!!

[davehaynes]

its been port polished, air flowed, high rise cam, straight through exhaust though that's why i really want to get it sorted and don't want to fook anything up.

[nova_saloon]

most likely the sender unit myt car did i replaced everythign and its still stayed the same, so spent loads of money doing all this to find out it was just the sender unit. but in ur case may be diff