405 Running Cold?

I have a 405 GRx4 2.0i.

Recently, on the motorway, at a steady 75 (ish!) the temperature gauge never
got above 70 deg C and the interior heater was lukewarm at best.

When in traffic (and stationary/crawling) the temperature will rise to 95
deg C then cool to 80 deg C when the fan kicks in.

What can I do to improve the temperature when running (it can't be running
at an optimimum temperature at 70 deg C!)

Tried already;

1. Temporarily blanking off about a third of the radiator - made about 1 deg
C improvement!
2. Checked that the fan wasn't always running - it wasn't!

Any more suggestions?

Cheers

Peter

 

Try checking that the thermostat is not stuck open. If you remove it from
the car, it should be closed.

Dave

 

I would change the thermostat. Normally cost about £5-10. Almost definitely
sounds like that's your problem.
Neil

 

Let me add #3

3. New thermostat - no effect!

Cheers

Peter

 

"Peter Sheppard" wrote in message > Let me add #3

Then new thermostat isn't working.
Have the cover off.... it should be closed when cold, and open when you put
it in hot water.

 

I've just got back from a few days holiday and noted that My 405 is behaving
the same way as Peter's is. I had made a mental note to change the Stat and am
very puzzled to read that he has changed it not no effect.
Once my engine has cooled a little, I might go and remove mine to check in hot
water.
I'll post my results.

Bob

 

Experiments complete.

At 82 degrees the stat is open a crack and at 95 is ifully open but evenat 70
degrees it does not shut fully and daylight can be seen through the opening.
WIggling the spring and the moving part of the valve can seal it fully ( by then
of course, it has cooled further)
Dunking back into the water bath at 70 it stays shut Ok but re-heating and cooling
to 70, it stays open a crack.

Maybe with the water pressure from the pump and the extra large radiator fitted on
the newer aircon models (mine is jan 1995) this is enough to cool the engine.

It used to sit steady at just over 80 on the gauge and now varies from 70 to 90
plus according to how hard the engine has been working and or road speed. In a
queue of traffic on Friday it rose to over 90 and switching the fans manually to
full speed ( a non standard modification I've made), quickly cooled the engine to
virtually 70.

I think a new stat is worth trying and suspect the hysteresis of the old one (the
difference between opening temperate and closing temp has increased. I've had the
problem beofre and not bothered to analyse it. Changing the stat then fixed it OK.

I still can't explain Peter's result after changing the stat other than he may
have got a duff replacement.

I'll get a new one in the week but now the clocks have changed, I'll not be able
to swap it in daylight until next weekend.

Bob

 

The old one was definitely naff! There was a loop of rubber floating
around the middle of the stat and I suspect that this was preventing
the stat from closing fully.

I will take out the new one and trial it in a kettle etc.

I am new to 405's (and very new to this GR4x4 version). The radiator
at the front seems huge (only 50% is covered by the fan) and it looks
like there is a mounting point for a second fan (unless that's for
LHD?) There is also one pipe at the bottom LHS of the radiator
(viewed from the bonnet looking into the engine compartment) that is
just blanked off. The other pipes seem to be (1) to the heater and
(2) to the thermostat (which seems fairly normal). There is also the
header pipe from the thermostat area.

I wonder if my rad is just too big! I've thought about blanking half
of it off. The engine gets to a good temperature when idling, its
just doing 70mph (honest guv) down the motorways that drops the engine
temperature (and stops the internal heater being effective!)

I'll try blanking it off and let you know what happens.

As an aside I've checked the indicated temperature against that from a
digital thermometer held in close contact on the outside of a heater
pipe and they are close to within a degree or so.

Cheers

Peter

 

"puffernutter" wrote in message

It's probably a multi-fit rad, that works across the 405 range. My 2 litre
STi has the same. The second fan is fitted to the turbo diesel models, (and
some n/a diesels), as they get used for load lugging and towing. Some of us
Citroen BX 16v owners fit a second fan to keep the temp down in traffic.

I'm a bit allergic to blanking rads, I've seen too many mishaps and blown
engines, and even a couple of fires caused by it. If the thermostat is
good, it WILL keep the engine, and hence the heater, hot. This has got to
be your best route.

 

Just to let you know, that a new stat (bought online from German Swedish &
French carparts - www.gsfcarparts.com £10.58 all in, arrived return of post) has
cured my problem. I can only assume that the waxstat elements leak a bit or
something and increase hysteresis.

Bob

 

Well done sir..... (Buffs nails on shirt) Nice to be near the mark
occaisionally