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[Rank]

Had a cooling problem with my 98 2.5 V6 Tourer which got hot in traffic very easily. Electric fan cuts in, brings temp down but then it heats up again and the cycle continues.
At speed, temp stays OK. Heater output was poor and LPG system kept switching back to petrol.

After changing the rad, water pump and temp sensors problem traced to secondary coolant pump which was then replaced.

Problem solved for all of 2 weeks. Temp started to creep up in traffic again and heater output got worse. On a trip back from Gatwick on Friday heater output barely warm and engine gets too hot at low speed.
I suspect that the secondary pump has failed again but am I unlucky with a rogue part or is there something that can cause these pumps to fail?
Help!

[Mike Collins]

If your secondary pump is the one mounted top right of radiator, when standing in front of the car, I believe that only runs after shutdown to cool the heads.

Is the overheating during running, how high is the temperature, do your front fans run when A/C compressor is running?

[Kevin Wood]

.. or is it the other pump near the header tank? I believe this only runs when the heater is on with the engine stopped however if it blocked it could cause the problem you describe. Clearly you have poor circulation around the heater matrix and LPG vapouriser. I'd be inclined to go over the LPG plumbing to make sure it is sensibly routed and no pipes are kinked.

If I'm right about this pump you could probably ditch it completely without too many complications.

Kevin

[jonathanh]

My secondary pump (underneath the header tank) is on its last legs.  runs fine when cold but slows down when hot.  As far as I can tell it has a permenant live supply whether the engine is running or not and whether the heater is set to hot or cold.  anyway for the last few months I've just unplugged it and all seems fine so I agree you can probably do away with it

[Rank]

If your secondary pump is the one mounted top right of radiator, when standing in front of the car, I believe that only runs after shutdown to cool the heads.

Is the overheating during running, how high is the temperature, do your front fans run when A/C compressor is running?

It's the pump by the header tank. Temp stays around 95 degrees with AC running (but it's cold at this time of year with no heater). With AC off the gauge goes up to 100 before fan cuts in and brings it back down. At speeds of above around 40mph there is enough airflow to keep gauge at 95 or just below. At lower speeds temp rises until fan cuts in at 100 degrees.

Pump was replaced in mid Jan (pump from main dealer at around £100) and everything was fine for a couple of weeks. I am just wondering if I'm unluckly with a faulty part or if there is something else that can cause these pumps to fail

[mark.adams]

Do all models (incl mine) have this secondary pump fitted??

[Mike Collins]

There must be start date or option that adds this pump, my 97 and 98 2.5's don't have it. My 2003 2.6 does.

I rerofitted it to the 98 in the hope of improving the heater output, hasn't really made much difference.

If you are getting that hot with present ambient temperature, I would suspect the radiator, I see you have changed it, was it new, or could it be partly blocked?

[Mike Collins]

I've just noticed you have LPG, the plumbing for that taps into the coolant circuit. Has it always run hot, could the LPG vapouriser be strangely plumbed?

[Rank]

I've just noticed you have LPG, the plumbing for that taps into the coolant circuit. Has it always run hot, could the LPG vapouriser be strangely plumbed?

LPG conversion was done when I got the car 3 years and 40,000 miles back. Everything was fine until early summer last year when it started to run hot in town. Had the rad and thermostat changed and found that the stat wasn't opening fully. This improved the situation but didn't totally cure it. Comiong into winter I found that the heater output was almost non- existant and it kept switching off LPG back to petrol so decided to change the water pump as a precaution. Took it back to the guy who did the LPG conversion so he could check that over at the same time. The LPG playing up was connected to poor cooolant flow as the LPG due to where the LPG sensors are.
Whilst in the garage they found that the secondary coolant pump had failed so replaced it. Everything was then fine for a few weeks. LPG system behaving itslef, no overheating even in traffic and loads of heat in the cabin- lovely.

After a couple of weeks it started to overheat in traffic again and the heater output has reduced until now it is barely warm. LPG system is taking longer to switch in and has started to cut out again at speed.

I'm assuming that the secondary pump has failed agin but why? It's only been in the car for about 6 weeks. Is it just a faulty part or is there something else that can cause premature failure?

[The Doctor]

Maybe the vapouriser has blocked? could you either rejoin the pipe ends that were cut to feed the vap. Put the cooling pipework back together as it should be. just to eliminate it.

Also worth checking all your vaccum hoses and heater controls work correctly... if the vap. was incorrectly plumbed regards the matrix flow control valve, it may now be showing as the vaccum hose prob prevents the circuit flowing correctly.

[Rank]

Thanks for the help guys. Problem seems to have been caused by a faulty diverter valve that feeds the heater matrix.
Secondary pump is fine.
Having replaced the Rad, thermostat, pump and secondary pump and now the diverter valve, I don't think there is anything alse apart from the heater matrix to go!!