overheating 405 !

wayne togher · Post by **wayne togher** » 23 May 2002, 01:53

405 grd 98000 g reg
ive been trying to sort my brothers car out. it overheats on long runs and only keeps from boiling by having the heating on flat out. ive flushed the rad, taken the thermostat out, checked for air and only found two bleed screws one on the rad and one on the thermostat housing?
the fans work but the rad only ever gets hot at the top, it might use a drop of water.
any ideas please im stuck!!!!!!!!!!!!!!!!!

alan s · Post by **alan s** » 23 May 2002, 05:48

I'm probably stepping into a minefield here as I own Citroens and not diesels at that <img src=icon_smile_wink.gif border=0 align=middle> but, having said that, this sounds like a typical air in the system problem. Unfortunately if you haven't had much experience with these sealed systems, it's easy to look in the "book" and read words of wisdom like "now simply undo the bleed screws until all air disappears and then tighten the screws" and come to the conclusion that all will be well. In some cases this will happen but in others it doesn't. Everybody who does any work on them would have been caught with this at one time or another.
There are several ways to get rid of it.
Fill the system to the brim (with the heater in the hottest position) and then starting at your lowest bleed screw, open and watch the level fall. Fill to the brim again & open the next highest bleed screw after bleeding from the last check your coolant level & refit cap.
Another is to park the car on a slope so that the filler cap for the coolant is the highest spot & again do the bleed screws from bottom to top. A trick used by many is one that was a necessity on the earlier Renaults; fit a funnel to an old radiator cap and this gives you a "header" of about a foot to 18 inches above the radiator. Fill until the funnel (or plastic container of larger capacity) is full and again slacken the bleed screws & tighten in the order previously mentioned. Leave the funnel/container full and start engine & let run for a few minutes. Go have a cuppa and remove when you return.
I have pumped (squeezed) hoses at the top & bottom of the radiator as well as in & out of the water pump whilst the bleed screws were loose so as to literally pump the air out of the system. If you've been trying to bleed it on a sloping roadway or driveway, you're beaten before you start.
Try the tips I've outlined & if still in strife let us know; personally, I think it's just a game of patience and doing things in a precise order. You'll get there. <img src=icon_smile_big.gif border=0 align=middle>
Alan S
BTW, I suggest that you take a look at the rear of the engine on the pipes leading to the heater for a bleed screw which is possibly (based on the Citroen experience) a brass headed allen key headed thing. I think most of these PSA motors have a bleeder to the heater; missing that wouldn't be helping your cause either.

JohnD · Post by **JohnD** » 23 May 2002, 23:55

Hi Wayne - The older Pug 405D's had a reputation for blocking their radiators, especially if the coolant hadn't been changed every two years. Many owners have had to resort to changing the radiator. However, don't ignore the overheating. XUD engines are brilliant, but they don't take kindly to too high temperatures - they blow their head gaskets.

JohnD · Post by **JohnD** » 23 May 2002, 23:59

PS - Look for another bleed valve moulded into the top pipe of the two going through the bulkhead to the heater.

Dave Burns · Post by **Dave Burns** » 24 May 2002, 02:01

Head gasket could already be a gonner, intake pipe to pump could be collapsing, or could even be getting sucked inward at high engine speed's, did'nt some BX's suffer from this.
I thought air lock at first but Wayne say's they have the heat on full to stop it boiling, if there is a air lock the heater in my experience hardly works.
Dave

wayne togher · Post by **wayne togher** » 24 May 2002, 02:45

thanks for all the advice, i will try it out on saturday and let you know.

wayne togher · Post by **wayne togher** » 16 Jun 2002, 02:32

sorted at last. i took a gamble on a new radiator and everything is fine now ,thanks again for the help.