Johnnycool

Hi i had read that the cooling flaps at the front should fully open when the AC is switched on - when i turn mine on the flaps only open 30% of the way and fans come on as expected - i was jst wondering which is correct , mine doesn;t sound right
when i switch it off the flaps do rotate thru the full open position before closing again so not jammed , plus i can manually cycle them easily with the motor screw.

btw my temp guage does aloways hover at the high end i know these aren;t accurate and its only got liek two markings 170 and 210 - sits on mark between these sometime going over a bit

any thoughts/confirmation/ideas always welcome and appreciated
cheers
Johnny

ammonman

Everything you describe is normal behavior for the system. The flaps go to 30% and fans get 8 VDC from the controller with AC on until refrigerant high side pressure passes 15 Bar (about 217 psig) at which time the flaps drive to 100% and the fans start ramping up to 12 VDC. (full 12 VDC by 20 Bar.) Your temp gauge is also working correctly.

Johnnycool

thanks a million for that great explaination ! ive just always been a bit paranoid about its behaviour espcially as that temp guage is such a bad guide and always seems to be not much to go after the 170 mark before the red zone !

cheers

Johnny

Johnnycool

hi , sorry for further paranoia but had to send a pic of where the guage was sitting this morning , outside temp only 3C as well ! , i had also got a coolant level warning this morning - topped it up before this
thoughts ? - too high ?

cheers
Johnny

FredR

First thing you need to do is to try and ascertain whether you have a false indication- unlikely but..?

The usual culprit that would cause such temperature excursion is when the impeller drops off the water pump shaft in which case the temperature will likely increase until the alarm goes off.

The dash display is driven by the sender on the right hand side of the water bridge when viewed from the front of the car, the alarm is driven from the temp2 sender on the left side of bridge. If you have an IR gun try shooting the temperature of the bridge. If the engine really is that hot your senses will probably tell you something is not right when you open the bonnet- you will likely "sense" that things are way too hot.

The impeller may fail for a number of reasons but a possible one is when the bearing goes south the seal fails as well so your coolant alarm may also be an indicator of such grief having taken place. We will assume your coolant did not freeze last week!

Johnnycool

hi , yep to be safe i have recently replaced all 3 sensors - rad , temp 2 and dash sender . Coolant replacement was done about 2 weeks ago but before this i was having to top it up every few weeks , this is the first top up since replacement .
don;t have an IR gun but maybe can see if i can borrow one , doesn;t feel excesively hot when i open the hood .
This temp guage has been slowly creepign higher over past few months and im getting more paranoid espcially with loss of coolant
impellar fail sounds pretty drastic - is there any other ways to check if pump has failed ? - not cure this would explain loos of coolany unless i just also have a small leak somewhere as well :-(

cheers
Johnny

Mrmerlin

NOTE when changing coolant is a good idea to inspect the HCV and short hose if these parts are older than 8 years it a good idea to swap them out,
also install a new T stat and rear sealing ring and coolant cap.

You can also look at the rear of the right side radiator tank see if it has white deposits this indicates a coolant leak ,
look along the top edge they crack near the swage.

If you have issues with the water pump then you will see the engine overheat in 5 mins or less,
if thats not happening then look at other things first.

FredR

Johnny,

Losing coolant is not normal and you need to find out where it is leaking from irrespective of anything else. That being said even if you are losing coolant and the system is not sealing you should not see a temperature indication like that especially when it is 3 degrees C ambient!

I stress the need to verify the temperature is a correct reading. If the indicated temperature has been going up it may indicate a false reading is occurring for some weird reason. Best thing you can do at the moment is a cooling system pressure test at 15 psig and see if it holds pressure- that tells you quite a lot in and of itself.

How old is your water pump and if replaced what make is it?

Johnnycool

yep totally agree - seems i have two problems - the joys of 928's :-)

im afriad i cannot verify the water pump make or when replaced - yes i know everyone please dont jump on this - its on the to do list for piece of mind , again was insured it was done but didn't couldn;t find it in history when car arrived - was 928 novice

just need time as usual to have a look around the system - i might order new thermostat and replace anyway as easy to do! i must check the heat matrix valve again as i replaced it a few months back - could be leaking down there i guess from when i disturbed the old one

cheers
Johnny

Johnnycool

i will also hook up my diag tool and see what the LH is getting from the temp II shoudl give me an exact value and see how it compare to guage reading !

Mrmerlin

JC when you fit a new heater valve you should also replace the short hose.
when you swap a T stat you should also replace the rear seal and O ring.
When you have cooling system issues you should swap in a new coolant cap.

FredR

That might be useful.

Johnnycool

ok guys - might be key piece of info i forgot - i had removed the fuse for the flaps and set them fully open before this last reading to see if it dropped overall temps as i'd read it can help .......... i put fuse back in - temp now right on the white line instead of over on same run/ambiant conditions so a big improvement - not sure if perfect but a lot better !

got a wierd theory that since flaps where fixed open the cold air from outside was hitting sensors and not allowing them to get a true reading therefore holding off on fan operation even thou internal water temp was higher then should be !
just a theory !
cheers

Bertrand Daoust

The main concern here is the coolant lost.

Like mentioned, do a pressure test and see if there is a leak.
If you loose pressure quite rapidly, you have a major leak.
External leak(s) should be quite easy to find although there is many hoses and junctions under the hood.

If you don't see any external leak, check every cylinder through the spark plug hole with a boroscope.
If you see coolant there, you have a bad head gasket.
But with the millage your car has, I would not worry much here.
Never had serious overheating problems?

How was the oil on your last oil change?
No coolant at all there?

Any oil on top of the coolant in the expansion tank?

Edit: How are the spark plugs? All the same color, or one (or more) are way cleaner?

Johnnycool

hi

i think coolant leak is minor i just need time to get look round all pipework :-) no actualt overheat ever , no coolant in oil - just changed last week , no oil in coolant - also changed last week , spark plugs all ok on last inspection but that was about a year ago !
cheers
Johnny