Over heating: hot spots: what are these?

[anthony1956]

Scenario: coolant header(expansion) tank is short of say 1 litre of coolant.

 

I have been roundly told this can damage the head gasket (R500 engine) because "hot spots" can arise where excessive heat is generated that does not appear on the temperature guage because it is localised.

 

I am interested to know more about this matter, if anyone can elucidate?

 

For example, how do these arise?

[Englishmaninwales]

Head gasket may already be blown, accounting for the loss of coolant. ☹️

 

Edited to say just seen you other thread, so this isn't very helpful ❗

 

Edited by - Englishmaninwales on 23 Aug 2006 14:35:19

[anthony1956]

😬 I'm considering coolants, also found a fascinating coolant thread here "Ethylene Glycol?"

 

and it's something I constantly wonder about..

 

Edited by - anthonym on 23 Aug 2006 14:41:13

 

Edited by - anthonym on 23 Aug 2006 14:41:40

[John Howe]

Hot spots/localised boiling, if this occurs between the deck and the head can lead to water evaporation, thereby leaving the residue of the antifreeze mixture turning to crystal form. The build of these crystals is not dissimilar to grass growing up from under the tarmac and will lift the head and thereby allowing the head gasket to blow.

 

I have yet to see a K series engine with a blown head gasket where the fire rings failed; it has always been this build up of crystals separating head from deck.

 

 

JH

Deliveries by Saffron, the yellow 230bhp Sausage delivery machine

[anthony1956]

John I would be very interested to know if the build up of crystals you mention can be impacted by the thread "Ethylene Glycol" here

 

From what subtsance are said crystals formed? (Silicates?)

 

A longish read, but some of Peter Carmicheal's messages draw it all together.

 

I'm just looking at comma's website wondering what the current recomendation is for R500 - suffering from info overload I think. And where/if they have a Swiss supplier... I'll see. NOW SUSSED here

 

Reading through search results for "hotspots" since forever - your reply was what I wanted to know.

 

Edited by - anthonym on 23 Aug 2006 16:48:30

[John Howe]

Whose to say what the crystals are formed from other than whatever is present within the anti freeze.

 

By choice I have always used Coldstream and mixed Redline Water Wetter with it... don't ask me why, I just do.

 

Coldstream is no longer available from any of my local Comma shops and is not listed on their web site, so I guess when I use up my last 5 litres I will turn to Xstreme red, that is unless I can find a pre-mixed propylene glycol option.

 

 

 

JH

Deliveries by Saffron, the yellow 230bhp Sausage delivery machine

[anthony1956]

Whose to say what the crystals are formed from other than whatever is present within the anti freeze.

 

ah, I thought you as in, which parts of what is present... iyswim

 

Edited by - anthonym on 23 Aug 2006 16:50:30

[The_ASH]

I thought that THE coolant for the K series was Comma Coldstream, it says on the can 'contains MonoPropylene Glycol' which used to come pre-mixed from Comma in 5lt plastic cans. I ran my 1.4K SS on this with some water wetter and it was fine. If you search back on Blatchat 3,4 or maybe 5 years I remember talk of something called micro-boiling which can occur if the wrong coolant is used. Basically what was said, was that, the coolant boils in certain hotter areas inside the head if the wrong coolant is used, and thus at these points erosion of the aluminium surface occurs. So eventually I guess you have a porous head.

 

Ashley Webster.

No longer becalmed in a sea of Caterhamlessness.

[Colin Mill]

The info that came with my car (2004) suggests using Xstream Red and that was what CC sold me at the time.

 

The localised boiling is one reason why I don't much go the way in which the header tank setup works on the car. With the large air space in the top of the header the system is not going to pressurise much by the compression of the air in that space as the coolant expands. Pressurisation must therefore rely on the temperature of the coolant in the header rising and increasing the vapour pressure over the hot coolant.

The header tank does eventually get hot but there is no active flow through it to ensure it gets up to the temperature of the head. Indeed its large bore connection is into the return from the radiator - the coldest part of the whole system

 

By contrast, older type systems with a pressure cap and expansion bottle pressurise quickly as the coolant expands (because there was little or no air trapped below the pressure cap.

 

Colin

[Myles]

there is no active flow through it to ensure it gets up to the temperature of the head.

 

There is if you fit Jenveys... The coolant spigot doesn't have a non-return valve, so in my installation (at least) there is flow through the thin hose that directly joins the head to the top of the tank.

 

Project Scope-Creep is live...

 

Alcester Racing 7's Equipe - 🙆🏻™

 

Alcester-Racing-Sevens.com

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[Colin Mill]

Hi Myles

 

Many thanks for that info - I must confess that I have given some thought to getting rid of that valve in the standard setup. It seems like just one more thing to fail with no real use, at least not in the 7 installation.

 

Colin