blocked pipe

[myoldjalopy]

Hello,
I went to replace the small hose between the water pump and the cylinder head as it was perished and leaking.
Then I saw the water pump pipe was completely blocked! It took me a good 15 minutes to clear it with an allen key (I needed something with a right angle to get into the pipe). It was a quite hard deposit.
Eventually it cleared and water came out.
What I want to know is why wasn't the engine overheating before with a blocked pipe?
Thanks,
Pete

[panky]

What you describe sounds like the by-pass hose, it keeps a small flow going through the pump until the thermostat opens to the radiator. It could be that your thermostat is stuck open (or there isn't one in there) so no flow was present through the by-pass and it's eventually clogged up.
Alternatively if the car has been laid up for a while and the pipe dried out it could have silted up

[MarkyB]

If that was blocked I'd be very concerned that the whole system needs attention, the pipes in the radiator are of a smaller diameter than the bypass hose.
Some drain cleaner A la Roy may be in order.

[bmcecosse]

Some of us block off / eliminate the bypass pipe intentionally - faster warm up, far better heater performance and no risk of the pipe bursting! The blockage there does rather indicate possible sludging throughout - so a good 'flush' is certainly recommended. If you changed the hose without removing the water pump (?) that rather suggests you have used the ghastly 'concertina' hose? A very bad idea...handy for an emergency - but as soon as possible, change it for a proper 'solid wall' bypass hose - and yes - you will need to remove the water pump, so have a new gasket 'in stock'.....

[myoldjalopy]

Gentlemen, thank you for your replies. It was, indeed, the by-pass hose I was talking about. Funnily enough, there was a small pebble(!) stuck in the hose which may have caused the problem. I don't think the rest of the system can be too bad as the car has never overheated.Also, the water that came out was pretty clean. However, I need to replace two other hoses and add antifreeze so will flush things out then for good measure.
As the hose was a bit awkward to fit, it can stay there a while! But will add a better replacement to my spares collection in the boot.

[MarkyB]

The mind boggles at how a pebble found its way there!
Give the rad a shake and see if it's got shingle in the bottom.

[katy]

will add a better replacement to my spares collection in the boot.

Wouldn't hurt to add a water pump gasket to your spares while you're at it.

[myoldjalopy]

Yes, that thought has already crossed my mind. In fact I think I have a pump gasket in my scullery. If so I will add it to the boot collection.............

[bmcecosse]

Better to take the time very soon to fit the correct pipe - rather than struggle at the roadside one dark & stormy night!

[myoldjalopy]

Yes, we get plenty of those down here in Kernow

[myoldjalopy]

Dear friends,

I did indeed have a water pump gasket in my scullery and, thinking further about Roy's doom-laden warnings about breakdowns on dark and stormy nights, and now that the evenings are drawing in, you will be pleased to hear that I whipped out the pump today and replaced the "ghastly" concertina hose with some lovingly cut heater hose and all is right again.

The water that came out was pretty clean, but the pump did have a bit of crud in its smaller pipe, no doubt due to that pebble.

Anyway, all good now, thank you.

Pete

[bmcecosse]

Well done Pete - I can sleep more easily tonight!