Overheating

[Steamoilking]

Hi looking for help and advice, my 72 c3 5.7l is overheating and using loads of water. On a 20 mile run mixture of traffic and 40 mph crusing its used 6 litres. It doesnt appear to be leaking having looked all over it, just boiling it. Cruisng the temp sits at 200 soon as you hit traffic lights or slow moving the needle goes into the orange and then obviously boils.
It has a new aluminium radiator but no expansion tank as its the air con version.
Aany advice please or somewhere i could take it to be looked at?
Thanks

 

[CaptainK]

Have you checked the thermostat to ensure it is opening correctly to go out to the radiator etc?

 

[Roscobbc]

As CapK sez - bung the thermostat (if it has one) in a jug of boiling water to see if it functions. Do you have an 'air lock' in the system somewhere? - you'll need to get some warmth in to the system and perhaps 'pull' a hose or two and bleed-off any trapped air. Has anyone messed with the timing (too retarded and it'll run hot). has this the same before new rad was installed? Did you replace water pump? (if run without antifreeze for a long time the impeller (if steel or cast iron) will corrode and loose effectiveness. Does it has a viscous fan (and is it working) Where is the 'lost' water going? is it being vented?. Have you checked for a blown head gasket? (so traces of water in oil - 'rainbow' effect of oil/combustion showing in water)

 

[Daytona Vette]

Could be a blown cylinder head gasket - does the oil have a milky white residue? check the dip stick
Are you blowing white smoke from the exhaust pipes?

Do you have electric fans? you may have a faulty thermostatic sender switch - you said the temp gauge needle sits at 200 when cruising and then boils in slow moving traffic, ie the sender is not working

You may also have an air lock, common if the system was drained and then refilled without opening the heater valves before re-charging with water

What area are you?

 

[Steamoilking]

As CapK sez - bung the thermostat (if it has one) in a jug of boiling water to see if it functions. Do you have an 'air lock' in the system somewhere? - you'll need to get some warmth in to the system and perhaps 'pull' a hose or two and bleed-off any trapped air. Has anyone messed with the timing (too retarded and it'll run hot). has this the same before new rad was installed? Did you replace water pump? (if run without antifreeze for a long time the impeller (if steel or cast iron) will corrode and loose effectiveness. Does it has a viscous fan (and is it working) Where is the 'lost' water going? is it being vented?. Have you checked for a blown head gasket? (so traces of water in oil - 'rainbow' effect of oil/combustion showing in water)

So i can check the stat thanks for that advice.
As for timing yes the garage who've had it in to service, check over, fix air con for three months did say they've adjusted the timing as ot wasnt running right?
Rad was installed prior to my ownership during resto. Not new water pump and antifreeze has been used, viscose fan is running ok, however im not convinced yet that the fan shroud has the edge sealant as per the manual.
Finally there are no traces of water in the oil or vice versa fortunately!
Im in Dorset area.

 

[Steamoilking]

Could be a blown cylinder head gasket - does the oil have a milky white residue? check the dip stick
Are you blowing white smoke from the exhaust pipes?

Do you have electric fans? you may have a faulty thermostatic sender switch - you said the temp gauge needle sits at 200 when cruising and then boils in slow moving traffic, ie the sender is not working

You may also have an air lock, common if the system was drained and then refilled without opening the heater valves before re-charging with water

What area are you?

Thanks for the heads up
No smoke, or oil in the water or water in the oil.
Viscose fan running ok not electric, in slow or stationary traffic needle moves to 230/250 steadily but quickly and i presume because the water is evaporating or venting through the rad overflow? You physically cant see water leaking from anywhere.
Where are the heater valves you mention situated please, thats something for me to check.
Thank you for your advice

 

[Roscobbc]

Earlier C3's can be marginal in terms of cooling especially on days like we've just seen at 30 degree plus. Firstly I'd be inclined to find out more info about the radiator that was installed - was an OEM styled replacement? (I have one of those on mine - (a DeWitt ally rad). Are all rubber/fibre sealing parts in place around the radiator? - is the OEM fan shroud in place? for a C3 radiator to work correctly in hot weather the seals and shroud have to be in place. Post an image on here perhaps. Remember that to work correctly all cooling air MUST come though the front grilles and only pass through the radiator. There is nothing wrong with the OEM cooling set-up IF it is in place and operating correctly. That is all I use on mine - I'd be lying if I said that the car doesn't get hot, really hot, and I 'cook' - but it doesn't overheat and usually keeps below 200 degees.

 

[Daytona Vette]

Heater controls inside the car on the centre console, slide for heat and that opens the system to allow the hot water into the matrix

Can you hear / see the viscous fan coming in? start it from cold with the hood up with one eye on the temp gauge and the other on the fan

Further I would test the water thermostat to see if it opens or temporarily leave it out all together, then I would bleed the system with the heater on the hot setting

May be a good idea to drain the block completely - core plugs need removing - you may find it crusty

Need to resolve it without overheating otherwise further damage may occur

The sealing around the radiator is important, so all the air goes through the radiator, possibly not causing your issue at the moment, but wise to get it sorted.

FYI When I once had an overheating issue with a sender switch I was able to cruise at an optimum speed on the motorway without any fans intervening, as it was self cooling, but below that speed the temp would be 200 plus, I was ok as I had temporarily wired in a manual switch to bring the electric fans on - what we learn from this is the fault issue was there regardless of speed - the speed just helped alleviate one of the symptoms of the fault, most likely the same for you.

 

[Roscobbc]

There's a lot to be said for Barry's observations. I mentioned erosion of water pump impeller due to continued use of coolant without an antifreeze content - if that has been the case (as was with the 427 cu in engine in my car) the lack of inhibitor will cause oem steel core plugs to rust through and leak with the rust flakes from and the inside of the block all falling to the bottom of the cooling galleries in the block, building-up and reducing the amount of coolant circulating around the block, creating potential overheating issues. The answer to this is a chemical flush of the block (perhaps not the ally radiator) - do you really want to do this? it could expose potential leaks from core plugs that are totally inaccessible whilst the engine is in the car.
Before I changed to the bigger engine I used some Radflush in the original radiator and cooling system as directed, drained it off, removed the lower hose and ran a garden hose through the engine for several hours. Surprising how much rubbish flushed out of it.

 

[Steamoilking]

Thanks for the advice so far certainly the timing has been changed all part of the recent service and recommisioning of the a/c which lasted all of 5 minutes before an a/c hose split ! Once it's stopped chucking ot down ill look at all the points raised. Certainly the fan shroud and its correct sealing. As for rust flakes and core plugs understand completely my previous being a road going traction engine with steel boiler so used to washout plugs and scale!
Ill put up some pics tomorrow but id like to say thank you for all your advice so far, keep safe

 

[Daytona Vette]

When I took my Vette to Topcats for some routine service jobs, plus a change of the coolant and a flush out of the old, as a matter of course they removed the core plugs to ensure escape of the water from the bottom of the block, I did cross my fingers, but they know what they are doing. (if access is an issue may be they did not get them all)

Interesting; antifreeze actually reduces the cooling properties of water (I only used de-ionised)

 

[Roscobbc]

De-ionised water and old school Glycol based anti-freeze. Redline 'Water-Wetter' may seem like an 'old wives tale' product (and its effectiveness is reduced slightly by anti-freeze) but contrary to what people might think it actually does work. When my '68 still had its 427 and stock (albeit knackered) it reduced running temperature 3 or 4 degrees. That was enough with other improvements (like sealing rad to shroud) to prevent it boiling over.

 

[Oneball]

How did you check the fan is ok?

When it’s cold and you first start it you should hear the fan change speed after 20 secs or so. When it’s hot and the fan should be working stick a rolled up newspaper into it, if it stops you need a new one.

 

[Chuffer]

Wow ! that`s the most high tech mechanical test i have heard of !! I guess if the fan is working ok , you just end up with a workshop full of confetti .
Or no fingers if you don`t let go quick enough .

 

[Oneball]

Sounds more dramatic than it is, the newspaper just bends out the way.

 

[Alben78]

Not sure if this is relevant but on our restomod C1 with an ex corvette 72 350 we suffered continuous problems with overheating and water being expelled through the overflow, no expansion tank. There were no signs of water in the oil either through the usual mayonnaise or a sniffer test and a compression test showed nothing. Having tried almost everything we eventually decided to strip the heads off. We found that the gaskets fitted to what was supposed to be a stock engine were shim steel. Replaced with the more normal gasket and the valves re lapped while the heads were off solved the problem completely. The car was bought in bits and supposedly all the parts sorted, the engine had obviously been rebuilt and looked like new......I believe that the steel gaskets should have been re torqued after a short time but nobody mentioned this when we purchased the car.

 

[Daytona Vette]

Of course other things can cause overheating, low oil, low oil pressure, oil with a very low viscosity - low oil and overheating - do not ask me, I was just paying the Bill

 

[Dazaa]

Do you have the front air dam fitted?

 

[Steamoilking]

Hi all, well after much exasperation, taking in all the advice from members and just, but only just resisting the temptation of the gas axe on the whole damn car and have done with it i made a discovery.
The heater hose from the top of the engine to the heater box that disappears under the ac compressor had a small split! Only by squeezing every hose whilst the engine was running did i discover ive put up a pic so you can see how small it was. Seems ok just see how it runs over the next week, thanks everyone for the assistance ill see you at Bicester for those that are going.

 

[Daytona Vette]

I think I may be correct in saying we were all off the mark - just a simple tiny split in a water pipe - cheers for letting us know your find, but if you do get another overheating problem you now have a great resource for what it could be!