I've had overheating problems. I've changed the thermostat, radiator cap, radiator, hoses. Between each change I properly bled the system. Still overheating.

I've done a lithium test and there is no combustion gases in the coolant. I've run a hose from the overflow into a bottle of water in the passenger seat and driven under load (foot on brake) and boost (car is turbo to 20psi) and no bubbles. I've had the valve train off and ensured all head bolts are tight (around 90ftlbs). So I don't think it is the head gasket.

Only thing remaining is the water pump. It does appear as if the coolant isn't flowing. Top radiator hose gets hot, bottom stays cool.

But how does a water pump fail? It's obviously turning and the pulley is. I guess it's just an impellor that helps circulate the water. Could it be so corroded as to not drive the water around?

Car has 68,000Km (about 43K miles), is an 00, and had the coolant changed about 2 years ago when I replaced the engine (and several times since during diagnostics).

 

Have you tried driving it with the thermostat removed?

There is a approx 1/2" pipe from the water outlet on the head to the water pump housing. It carries hot water to the rear side of the thermostat and is responsible for opening the thermostat. Is this still in place?

Look really closely as the tubes in the radiator. I've seen cases where the tubes swell closing up the space between the tubes, crushing the fins and leaving little room for airflow.

When the engine is hot the whole radiator should be getting hot. If not either the thermostat isn't opening, or the waters not being pushed around.

You didnt by any chance stuff rags into any hose ends or pipes during maintenance? The number of times those wads of rags get left in a system surprises me. ( Ever seen a rag go through a turbo)

 

I haven't tried with the thermostat removed but have often thought about it. Unfortunately it involves draining the coolant and bleeding again just to run a test.

I've heard of the tube running to the back of the thermostat and I'm sure it's in place as it would take some work to block it and I was the one who put the engine back in after the rebuild. It all worked then. Pretty sure it's not rags either.

That's why I'm thinking pump.

 

The car is at a mechanics at present (I know, against my religion but I don't have the test equipment and they owe me for some network work I did) and will have the cooling system pressure tested. Is that enough to confirm my head gasket is ok?

 

I'd remove the water pump and check the vanes for deposits.. it happened to me.. so much gunk on the vanes that the pump was not able to flow anymore... just my .02.. good luck

 

Thanks Joe, think I'll give that a try. Did you clean or replace?

 

replaced.. the bearing had play as well....

 

Cheers. Will pull apart and inspect before making a decision.

 

Let us know how it turns out....

 

Shall do.