cold radiator

Hi folks,

the heater matrix, HG, timing belt and (supposedly) a new thermo done recently by LR inde in Penrith, paid for by the trader I bought the car off (HG blown when purchased unbeknownst to me or him).

Having got it back earlier this week, I took it to my local mate for service; the plugs were well old, no oil/filter change, and a cold radiator.... the coolant is definitely circulating but not through the bottom hose (cold) and hence not through the radiator....

No coolant loss, top hose harder than it needs be, heating all working as it should be. It has, at some point had the thermo mod - grey unit in front of engine.

What could this be apart from a faulty thermo? We're going to put a T junction where the thermo should be sometime next week to eliminate this as the culprit but anyone any ideas??

Ta
E

This may be rubbish but ...I think the theory is the rad is so big it cools the water quite quickly whilst the car is moving .
you may have to leave the motor ticking over till it gets hot enough to kick the fans in
with a bit of luck the thermostat will then open.
I know I was worried the first time I checked the bottom hose.

edge said:

This may be rubbish but ...I think the theory is the rad is so big it cools the water quite quickly whilst the car is moving .
you may have to leave the motor ticking over till it gets hot enough to kick the fans in
with a bit of luck the thermostat will then open.
I know I was worried the first time I checked the bottom hose.

Click to expand...

This^^^^

Let me explain why.

The cooling system (rad and fans) used in the 1.8 is also used in the 2.5 V6. The V6 engine's cooling requirement is almost twice that of the 4 cylinder 1.8. Then additionally the V6 has to cool the auto box using the same coolant as the engine which puts more strain on the rad. Then the system is designed to cool the engine/ auto and IRD in the hottest places on the planet !! It's little wonder the bottom hose stays cool here in the UK during winter
I expect your stat is working just fine, it simply bleeds such a small amount of hot water into the rad that it's cooled rite down before the water has got to the bottom hose.

I expect your stat is working just fine, it simply bleeds such a small amount of hot water into the rad that it's cooled rite down before the water has got to the bottom hose.

Click to expand...

Thanks Nodge & Edge...

I understand the explanation; would the radiator be *stone* cold too? My mech mate thought the coolant wasn't getting past the thermo....

Ta
Ez

PS I've not had it long but I can't recall hearing the fan kick in..... and she does get to temp very quick compared to my saabs - say 3 minutes...

Ez said:

Thanks Nodge & Edge...

I understand the explanation; would the radiator be *stone* cold too? My mech mate thought the coolant wasn't getting past the thermo....

Ta
Ez

PS I've not had it long but I can't recall hearing the fan kick in..... and she does get to temp very quick compared to my saabs - say 3 minutes...

Click to expand...

The rad on a 1.8 during the winter could well be stone cold. The cooling fan is controlled by the engine ECU so if the engine is'nt hot it won't come on. The very best way to get the engine up to fan temp is hold the revs at 2,500 rpm for some time. This will eventually kick the fan in. The engine will warm up from cold according to the gauge vary fast although the gauge shows normal temp with the engine between 75°C and 115°C.

The cooling fan is controlled by the engine ECU

Click to expand...

aaah; so there is no thermo temp sensor other than the engine ECU and the thermo opens because a bimetallic? strip or equivelant is activated if the coolant get too hot in situ?

I'm thinking that same fan ECU must control other functions, so unless I have other symptoms, it's working....

I guess I'm a bit (very!) worried about another HG failure and want to take every precaution against this...

Ta
Ez

Ez said:

aaah; so there is no thermo temp sensor other than the engine ECU and the thermo opens because a bimetallic? strip or equivelant is activated if the coolant get too hot in situ?

I'm thinking that same fan ECU must control other functions, so unless I have other symptoms, it's working....

I guess I'm a bit (very!) worried about another HG failure and want to take every precaution against this...

Ta
Ez

Click to expand...

The engine ECU will put the fan on but only when the engine is hot enough to do so. Don't go by the gauge as they are deliberately inaccurate!! The engine ECU knows exactly when cooling is required. The thermostat is a PRT or Pressure Release Thermostat. So it will keep the water in the engine circulating but will pass some to the rad if the water pressure exceeds a pre-set figure which is rpm controlled. It will also send hot water to the rad according to the water temp.