Thermostat or water pump????

Hi guys, just had the air springs replaced on my TD5 (2002) only have something else happen two days later. My wife had complained that there was no hot air coming from the heater just cold air pumping out, the next day I tried it and for the most part she was right although there was the odd gust of hot air coming out from time to time but the biggest problem was that the temperature gauge on the dash suddenly dropped into the blue and the car went into "limp" mode and I headed back home. I checked the water expansion tank and it was full and I squeezed the water pipe from the radiator into the engine and I could hear a "squelching" sound from the expansion tank so I guess there isn't a blockage so I can only assume that it's either the water pump or thermostst at fault. Does this seem logical or can anyone suggest something I might have missed?

Cheers
Al

Poss air lock, If a thermostat fails shut the heating will still work. The fact that your temp gauge is going into the cold when driving could also be because of an air lock. I don't know what they use for the temp gauge sender but i had a simullar problem with a mondeo, temp gauge dropped to cold, engine went to limp mode, key off and restart all ok for 10 miles then did it again. This turned out to be the sencor that tells themodule the engine temp (combustion temp) the module then works out the coolant temp, diagnostic machine should be able to check this.

Cheers, thanks for that. What I'll try next is to open the bleed screw on the pipe and check for bubbles (whilst running the engine of course). My Haynes manual is packed away due to moving but as I remembered this is the way to do it. I had a similar problem before, I used to forever be topping up the tank with water until I discovered the leak which was fixed in the summer, I changed the anti freeze after cleaning the the radiator and pipes/block with Radclear and all seemed well until now. Is this a common problem with disco TD5's?

Did you put rad clear through the whole system?? Just anouther thought poss head gasket starting to fail :behindsofa:

Yup, if I remember correctly I followed the instructions exactly...so what are the signs of a leaky head gasket? sounds expensive ;-(

fella31 said:

head gasket? sounds expensive ;-(

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before you go ahead get it tested first if your thoughts are swaying towards hg failure !!!
your usually get the coolant pumping back in the header bottle and possibily over heating symtoms .
not an expensive job to do yourself , but would defently need the head skimmed if your handy with spanners will defently cost below £100

have read its on a td 5 so it may cost a lot more

Yup, it's TD5 allright! I'm not too bad with cars I've changed clutches and a head gasket on a pug but I don't think it is that as I haven't seen and problems with overheating so far, I'm not sure about coolant pumping back in the header bottle. How would I know if that's the case?

initial things to look at so far are the thermostat, expansion cap dn water pump. To see if the water pump is working you could try squeezing the top hose while someone revs tha engine. If the thermostat fails it will still alow coolant past as it has 2 parts to it. It has the temp related part and a pressure related bypass valve that is operated when the engine revs exceed 1500rpm. If any of the 3 named parts fail it could cause the symptoms that you have.

If you remove bleed screw on tickover then expect jet of water to be about 5-6" high. Then rev it and it should hit the underside of the bonnet if waterpump is OK

Below 1500rpm the bypass valve in the thermostat forces coolant through the heater matrix only, but above this (and when up to temp) through the main radiator as well. So check if it blows cool only below 1500rpm and then gets instant warmth when you rev it.

I added some K-Seal to my TD5 and it killed the thermostat and overheated the motor within 10 mins of adding it.

Car currently in bits as I change the head gasket and leaky PAS box. Mine was overpressurising and blowing water out of the header tank. It would also build up air in the system which you had to keep an eye on to prevent overheating. If you slacken the bleed screw off a bit then the coolant should flow freely with no air bubbles. Mine used to come out like the froth of a pint of lager

TONY

I had an airlock but that pushed all the fluid out of the system. Since the initial symptoms does the AC fan run all the time and cant be switched off via the dash? That also seems to kick in as a 'save the engine' default setting. I believe you'll need to clear the fault via hawkeye etc to switch it off.

I'm wondering if it could have something to do with the electrics or maybe connections as the needle just droped down into the blue as if it became disconnected or something like that. Surely if it was the thermostat it would go up or down gradually?

fella31 said:

I'm wondering if it could have something to do with the electrics or maybe connections as the needle just droped down into the blue as if it became disconnected or something like that. Surely if it was the thermostat it would go up or down gradually?

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Water temp sensor is on the coolant elbow on the right hand side of the cylinder head (as view from front of vehicle) where it goes into the top hose

T

Hi guys, thanks for your updates. I think the problem might be sorted now, I undid the bleed screw on the hose slightly and there were some bubbles coming out but not a huge amount. I removed the screw entirely and a jet of water about 5" shot up so I take it the water pump is okay I also cleaned the electrical contact by the hose and gave it a burst of WD40. It ran fine after that, heaters also working although the drivers side gets hotter than the passenger side for some reason? So I take it that there must have been an air lock, but would that have caused the temperature guage to drop so sharply, as I said it just "fell" to the bottom? Cheers