Vapour locks in cooling system

[gdr]

Back to the old problem of cooling. I seem to have a problem with air/vapour getting into the cooling system and getting trapped in the radiator. After fully bleeding (I think) the cooling system, car will run fine in all conditions including traffic for some time, but eventually (after an hour or so) starts to blow water out the expansion tank (which was 1/3 full when cold). Also noticed this happening after some hard trackday use. This happens at relatively low indicated temps, 90C or so. This is not normal expansion, it blows out more than volume of expansion tank. Temperature spikes up to 100C then occur as I think the pump might be cavitating on pockets of vapour and problem gets progressively worse. System then requires bleeding down again which is not fun when hot. Car normally runs at around 80C. Sender is in cyl head. The 3/8" hose from top of radiator should prevent air locks, but its routing alongside main rad pipe as recommended in manual appears to allow an air lock to develop with the car horizontal. By jacking up the rear high (or parking nose down a slope), I get a lot of air coming out of the system.
I've tried various bleeding methods and system appears to be sealed OK (holds pressure).
Has anyone experienced this problem, or got any suggested solutions?
Thanks.

[doc_fudge]

GDR,

Is it possible that you have a blown head gasket?
This would explain your situation (Fully bleed system and then get pockets of air at low temps).

Did you notice excessive water vapour coming out of the exhaust when the car is running?
Maybe check your sparkplugs...when the car cools, some coolant may be sucked back into the cylinders.

Although having said that, you may not find anything in this regard as if the system holds pressure, then maybe vapour is only entering the cooling system under pressure due to high combustion gas pressure, but head gasket is still good enough to prevent back siphoning of the coolant.
Still check anyway as if the problem gets prgressively worse than these things may show up.

Im just having a wild guess...and I hope Im wrong.

Andy

>> Edited by doc_fudge on Sunday 14th September 10:48

>> Edited by doc_fudge on Sunday 14th September 10:50

[GreenV8S]

Sounds like your system is not degassing properly/at all. I may be able to help but I would need a fairly clear idea of the layout of the system (what connects to what, pipe sizes, heights).

[gtrclive]

Just a note the expansion tank should be empty when cold, ie. fill the swirl pot to the brim, and expasion tank empty. Otherwise there might not be enough room for expansion.
Is the bleed tube from the top of the radiator crimped any where ?

[ultimaandy]

My expansion tank is empty when the engine is cold and half full when hot.....

[gdr]

hmmmm. Need to investigate further. Hope its not a head gasket although can be fixed easily enough provided I've not warped a head. Good system pressure makes me think not. Will check the air bleed is not blocked and run with expansion tank empty at cold for a bit, see what happens. I might also rig up an alternative air bleed hose from rad to exp tank mounted slightly higher (along top chassis rail) to see if this helps system degas. Will keep you posted.
Thanks

[jschwartz]

The two caps for the Swirlpot and Expansion tank are different. Make sure they're on the right tank. One has a pressure relief and one doesn't. Can't remember which goes where right now.
jeff

[gdr]

jschwartz said:

The two caps for the Swirlpot and Expansion tank are different. Make sure they're on the right tank. One has a pressure relief and one doesn't. Can't remember which goes where right now. jeff

Got that one covered - pressure relief cap on expansion tank - but would be bad if you got it wrong way.

>> Edited by gdr on Monday 15th September 19:53

[US-GTR]

Alongside the thermostat, drill a 1/16th (1.5-2mm) hole to allow air trapped beneath the thermostat to travel out to the swirlpot. If you would like more detailed information, E-mail me off list.

[Gordon-3sigj]

Hi, I have a sports, had it for 17 years and it’s a 97. I’ve always had problems with it getting hot and dumping steam and water out.

I’ve got the biggest all aluminium multi row rad fitted. 2 x max capacity facet fans. Manual fan setting stat. Performance water pump. Now, no thermostat. My issue is under normal running it’s fine. Runs between 90-96, fans set at 94. Problem is they once it gets over 98 it never recovers. So a fast blast brings it on of hot days in traffic!! The old engine was a Huddart big revving 5.7 which I changed to a big torque 6.3 stroker Also by Mike Hiddart. Both set ups have done exactly the same. I’ve tried coolants, wetters, Manifold wrap, fans on constantly and an oil cooler in the side pod. Nothing changes. All suggestions are very welcome 🙏

[BogBeast]

Gordon-3sigj said:

Hi, I have a sports, had it for 17 years and it’s a 97. I’ve always had problems with it getting hot and dumping steam and water out.

I’ve got the biggest all aluminium multi row rad fitted. 2 x max capacity facet fans. Manual fan setting stat. Performance water pump. Now, no thermostat. My issue is under normal running it’s fine. Runs between 90-96, fans set at 94. Problem is they once it gets over 98 it never recovers. So a fast blast brings it on of hot days in traffic!! The old engine was a Huddart big revving 5.7 which I changed to a big torque 6.3 stroker Also by Mike Hiddart. Both set ups have done exactly the same. I’ve tried coolants, wetters, Manifold wrap, fans on constantly and an oil cooler in the side pod. Nothing changes. All suggestions are very welcome ??

Well, I have a 97 Sport with a Huddart built SBC.. I am running Evans NPG coolant with a low-pressure cap, a standard rad (for the moment - it has sprung a leak) and updated fans. I also run a big oil cooler in the side pod. It never boils over, but it used to get hot, so I would cut the fans in early. Now have Holley fuel injection ECU managing the fans through a corvette fan controller and it works a treat. I now spend more time monitoring the oil temp in hot weather. I suppose on really hot days and spirited driving the oil temp gets up there but I never worry about it spitting coolant.

[ROWDYRENAULT]

Don't forget the bleed lines off of the heads back to the radiator. I don't remember how many steam ports were on my L.S. in GTR1.0 but GTR 2.0 has All Pro heads on a RHS block and it has 4 ports one on each end of both heads. All Pro obviously felt that this needed to be addressed. lee

[Gordon-3sigj]

Yes guys that’s a massive help. Ever since I’ve had the car it’s had the pressure cap on the plastic expansion tank..... swapped and now appears to run excellent. Can’t believe it’s that simple 🤪. Thanks guys

gdr said:

jschwartz said:

The two caps for the Swirlpot and Expansion tank are different. Make sure they're on the right tank. One has a pressure relief and one doesn't. Can't remember which goes where right now.
jeff

Got that one covered - pressure relief cap on expansion tank - but would be bad if you got it wrong way.

>> Edited by gdr on Monday 15th September 19:53