IS it the water pump?

[britdan26]

Hi all

My chim has developed a problem and I have managed to convince myself the cause of this problem is the water pump. Before I spend out on a new pump I thought I would run my conclusion past all of you incase I am missing something really obvious.

Over the last couple of weeks my car has developed a habbit where by after about 5 mins of driving the engine stutters and runs as though it is only firing on about 5 or 6 cylinders. This lasts on and off for a few minutes until the engine temp reaches about 75 degrees at which point it will drive normally for the rest of the journey. (Or at least it did)

About 45 minutes into a journey yesterday the engine stuttering started again and I noticed my engine temp rising, this was followed by a smell of burning rubber and then the stuttering stopped, the engine temp returned to normal and all was well. As the battery light did not illuminate I presumed the fan belt had survived its ordeal and continued with the journey. After about an hour I was home having suffered no recurrence of the problem. At home having looked at the fan belt something has definately caused the belt to wear.

Without looking at any diagrams of the water pump I have a theory that a bearing in the pump is partially collapsed and occasionally jamming causing the symptons I have described. Does this sound plausable or has anyone else had a similar problem?

Thanks in advance for any advice.

[lwt]

The pump went on my RR (same serp engine) - try grabbing hold of the pulley and try to move it side to side (hard to describe but you want to try and waggle it as if trying to move it out of alignment with the belt). Any movement is bad. The pump can last quite a while like this (!) but the impeller will be machining metal off the inside of the pump casting.

Ian.

[GreenV8S]

Seems unlikely, by the time the bearing was that bad the movement on the shaft would have wrecked the seal. Suggest taking the belt off and spinning the water pump pulley by hand, if there are any problems it will be immediately apparent. Is it possible that it's simply loose and slipping? The engine running problems may be due to a lack of water flow upsetting a coolant temp sender?

[britdan26]

Thanks for both pieces of advise. There is a small amount of play on water pump pulley when I waggle it, small being only just distinguishable by my hand so I guess less than 0.5 of a mm either way from its resting position. When turning the pump by hand, it does turn freely throughout its entire revolution. The belt belts tension is slightly out but as it shows signs of wear I will replace anyway.

I guess the most logical step is to replace the belt first, ensure it is at the correct tension and see if the problem persists. Thank you both, an extra opinion or two certainly helps.