weird coolant question

[quagmire]

hi guys,after almost 12 months of pretty much trouble free motoring my overheating problems have come back again.....arggghhhhhh!
the weird question is.... with the engine running and dalek cap removed i can see the coolant return to the tank only when i rev the engine at say 3000rpm but its just a pissy little drizzle.is this right? i would have imagined it would have been a pretty strong flow? your thoughts please....cheers ben

[T'Onion]

thermostat stuck ? maybe pump on the way out

[quagmire]

sorry mark i meant to mention that thermostat has been removed,but it was as poor before! pump was from gsf about 13 months ago.i do about 400 miles a week in the van tho so i guess it could be the pump?

[T'Onion]

belt ok ?

[quagmire]

belt is fine mate.i spoke to james earlier but he couldn't remember how the flow was returning to the tank on his,could it be the small bore pipes are blocked?

[jamesc76]

Liek I said earlier pull pipes off and blow um through check there all clear spoke to a few lads at work and they said the same for the pipes to swell up and bre hard theres either a big amount of air really trapped or a pipe is blocked!

[silverbullet]

Running without a stat is really asking for trouble.
It's a common mistake to think that no stat = no flow restriction, so no overheating. The pump needs the back pressure to work , otherwise it will just cavitate at higher rpm/impeller speed (that's thrashing around and making bubbles because of no pressure) so you then get localized boiling because the water flow stagnates all over the place.
In racing circles a restrictor disc is used when there's no stat, but the hole size has to be arrived at by experimentation (and using temperature tell-tales).
That's why the flow to the header is a dribble.
Put a new, tested, working stat in and get those pipes checked out, along with your rad before you cook it.

[quagmire]

update. i removed most pipes in the engine bay and especially the large clear one that goes all around the bay and i found it was almost completely blocked with a piece of rubber gasket(probably from previous water pump).this along with some "pooh" in another one of the pipes was restricting the flow of coolant around the system!
i cleaned it all out,bled the system and the flow is about 10 times what it was!god knows how i haven't bolloxed the engine altogether but everything seems to be running well at the moment,apart from a small drip coming from the plastic flange pipe that goes to the water pump from the right hand side.hopefully its just the gasket.
cheers guys for the advice