Water Pump Flow/Volume

[Splod]

I hope this is in the right area of the forum.
I am having overheating problems recently, which seem to come on all of a sudden. The old girl would only run hot on a long run on a hot day, but never boil. Just recently she decided to boil on a relatively short run at only 80km/h. (The ambient tepmerature was 43 degrees, but not unusual for this old FC.) The first half of this trip the FC stayed around 2/3's up the gauge, but quickly rose to boiling for the last 50kms of the trip. It was almost like something had broken or failed.

I waited (in a pub) while it cooled down and refilled the radiator and set off home, but it boiled again within 10kms. Thought it might be heat soak from previous overheating so I parked at a friend's place and retrived it in the morning. Got very hot on the run home doing only 60km/h. (Much cooler this morning at only 33º)
I pulled out the thermostat and noticed the water pump would only pump into the radiator at about 1500rpm and above?! Is this normal? I would have thought the water should be constantly flowing at idle, even if not at a great rate. I had put a new rare Spares water pump on it about 9 months ago.

I have a new thermostat and radiator hoses. Since the boiling incident I got my radiator recored with a heavy duty core, with new radiator cap. I've tried with the heater on and off, but she still gets hot very quickly. Took it for a run at midday today, (outside temp is 40º so I thought it would test it out nicely) - it boiled again! I know it might seem hot for those who live in the colder climates of Sydney etc, but this is normal for my FC, which until recently had no problems with warm weather.

I have flushed the system with a hose connected to the heater outlet to try and eliminate any air pockets. The block was reverse flushed professionally when I put the new water pump on, and I run coolant in it all the time.

I keep coming back to the water pump, because although it is relatively new, it doesn't seem to have much flow. I removed it to make sure the shaft hadn't let go of the impellor, and everything looked OK and as I would expect. The impellor doesn't seem to have much bite on the "Blades" if you could call them that. But that is the way it was cast, it hasn't been eaten away or anything.

Additionally I have checked the timing and that seems OK.
I don't think I have a blown head gasket, but I can't rule that out without removing the head. No bubbles in the water, water in the oil, etc
My FC is running a stock 132 grey motor.

Any help or ideas would be appreciated.

[Harv]

Could be a crook pump - mine pumps out at idle.

Some ideas:
a) pull the thermostat and  check the model thermostat installed. Standard thermostat has a "start to open” temperature of 160ºF (71ºC), with a hotter “start to open” temperature of up to 173ºF (78.3ºC) used to improve the heater performance. Tridon part numbers are TT1-160   for the 160ºF thermostat and TT1-170 for the 171ºF unit.
b) whilst the thermostat is out, test it in a coffee cup of hot water to see if it is opening fully.
c) leave the thermostat out temporarily and drive the car. If it doesn't boil, consider using a high flow thermostat (Tridon TT2000-160 for 160ºF or TT2000-170 for 171ºF).
d) check the lower radiator hose isn't being sucked in (crimped) at high revs.
e) check that fan belt tension and check the pulley/belt for signs of slippage at high revs.
f) check the radiator fins for blockage or fouling - mud, dust, insects etc.
g) check radiator cap is correct unit, and not open-type.

Cheers,
Harv

[mcl1959]

I haven't seen a R/S water pump for a while, are the impellers cast like originals?  They should have small tolerances between components. Some cheap water pump impellers were made from pressed steel which wasn't very good.
It does sound like a head gasket or cracked head, but this usually happens after the car gets hot, not before it gets hot.

Ken

[Splod]

Harv...

As I stated, my pump doesn't pump out of the top hose at idle, so you may have a point there. Bit expensive to swap out at over $100 just to eliminate the pump, unfortunately, but a bit cheaper than Ken's suggestion of a head gasket/cracked head.   Might have to bite the bullet and buy a "spare".

a) I bought and installed a 71ºC thermostat which I have in at the moment. I took the last one out when it boiled and ran home with no thermostat - no difference.
b) Both tested and work OK.
c) See "a" above
d) I installed new radiator hoses and the bottom one has a wire coil inside to prevent collapse.
e) New fan belt fitted and double checked for tension
f) Brand new (recored) heavy duty radiator in it now - perfectly clean and smells of fresh paint - no difference
g) Checked cap for recovery version, which it is not. Bought new one when it first boiled and got yet another new one with recored radiator - still no difference.

Thanks for your help Harv, it is appreciated.
Cheers
Joe

==================================================
Ken (mcl1959)...
The water pump has a cast type impellor, but I notice the cutouts/fins in it are deeper on the fan side of the pump as opposed to the shallow ones on the engine side. I would question whether the impellor was correctly fitted to the pump except for the fact it worked well for nine months, and I have only just had this overheating problem in the last two weeks.

As for the head gasket or cracked head, well maybe, but as you say it usually happens after overheating but not before. I'll have to do a compression test and maybe talk to a mechanic to see if I can test the head theory before I pull it off. Then again I may as well change the gasket anyway. I can't go on like this.

Thanks for your help Ken. All ideas are taken on board and at the very least they help me feel I am not missing something obvious.
Cheers
Joe

[Harv]

I'll have to do a compression test and maybe talk to a mechanic to see if I can test the head theory before I pull it off. Then again I may as well change the gasket anyway. I can't go on like this.

Joe,
Your local radiator shop can probably fit a test cap to the radiator, and manually pump up the cooling system pressure. If it won't hold pressure, then a crack/gasket is likely. Slight chance that the crack is only opening when warm (and won't show up on the test) but unlikely. Pity your not in Sydney - I've got the gear here to do it. Some shops can also electronically sniff for combustion gas in the radiator header tank.

Alternative is to run an exhaust analyser over it and hunt for more water than normal in the exhaust gas, though few shops have this ability.

Cheers,
Harv

[Splod]

Thanks Harv,
I will call in to the place that recored my radiator this Monday and see what they can deduce. I'll pass on your advice and see if they have the equipment to do all those tests.

Cheers
Joe

[Splod]

Latest update:-

A blown headgasket complete with cracked head!
A water pump that doesn't pump when at low RPM OR when hot! Not sure why, but they are the conclusions of rigorous testing on the pump.

So... now I am after a good head to suit my 132 Grey Motor, one that can be transported out to Mildura Vic 3500 - any takers?

Cheers all, and thanks for the help.

[mcl1959]

I have a couple of good heads (not tested, but they came off running motors). Don't know how you would get them to Mildura though.

Ken

[Splod]

Freight is the problem with living in the country areas, as many of the members would testify.
Fatboy has put me onto a bloke who may be able to help me. I'll let you know how it goes.
Cheers
Joe