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Clas­sic cool­ing sys­tems can of­ten strug­gle to cope with mod­ern driv­ing con­di­tions, es­pe­cially when tem­per­a­tures start to rise. We look at what up­grades are avail­able to keep things cool.

Classics Monthly - - Contents - WORDS Iain Wake­field

About cool­ing up­grades. We look at what’s avail­able to keep un­der­bon­net tem­per­a­tures un­der con­trol.

F ol­low­ing the open­ing of the first sec­tion of the M1 in 1959, a steady stream of over­heated ve­hi­cles was towed off the mo­tor­way with clouds of steam bil­low­ing out from un­der­neath their bon­nets. This sad state of af­fairs was mainly due to the ma­jor­ity of mass-pro­duced cars built dur­ing the pre-mo­tor­way age hav­ing a poorly de­signed cool­ing sys­tem that was sim­ply un­able to cope with ex­tended pe­ri­ods of flat out mo­tor­ing.

Cars pow­ered by a side valve en­gine usu­ally had a non­pres­surised thermo-syphon sys­tem based on the prin­ci­ple of nat­u­ral con­vec­tion to feed coolant from the en­gine into the ra­di­a­tor rather than a me­chan­i­cal wa­ter pump. Long stints of fast run­ning or sit­ting in a traf­fic jam would of­ten cause en­gines cooled in this man­ner to rapidly over­heat and even­tu­ally seize up.

To keep en­gine tem­per­a­tures un­der con­trol in a side­valve pow­ered up­right Ford Pop­u­lar, Aqua­plane pro­duced an af­ter mar­ket me­chan­i­cal wa­ter pump that could be fit­ted to the Ford’s 1172cc top hose to as­sist coolant to cir­cu­late around the sys­tem more ef­fi­ciently. In those early mo­tor­way days even cars with a me­chan­i­cal wa­ter pump fit­ted as stan­dard reg­u­larly boiled over when driven hard.

Hot wa­ter ex­pands at a rapid rate and rises as its den­sity de­creases. Ex­ces­sive heat drawn away from the en­gine into the cir­cu­lat­ing coolant is re­ferred to as heat load. As man­u­fac­tur­ers in­tro­duced new mod­els with lower bon­net lines, en­gi­neers were re­quired to de­sign en­gines with pow­er­ful wa­ter pumps to pro­pel greater vol­umes of hot coolant through the ra­di­a­tor to re­duce the heat load. The faster an in­ter­nal com­bus­tion en­gine warms up, the more ef­fi­cient it be­comes and back in the days of black and white telly a pop­u­lar (and cheap) up­grade to en­sure an en­gine warmed up quickly on a cold and frosty morn­ing was to place a piece of card­board in front of the ra­di­a­tor grille.

For­get­ting to re­move a tem­po­rary blind like this would of­ten re­sult in the en­gine boil­ing over. A more per­ma­nent so­lu­tion was to fit a spe­cially tai­lored ra­di­a­tor blind, which could be raised and low­ered from in­side the car by pulling a cord lo­cated un­der the dash­board.

To­day there’s an im­pres­sive range of far more so­phis­ti­cated ways to up­grade a clas­sic cool­ing sys­tem rather than us­ing a bit of old card­board. Some of these up­grades are rel­a­tively cheap and easy to in­stall, while oth­ers are more ex­pen­sive. Fol­low­ing is a se­lec­tion of pop­u­lar af­ter­mar­ket cool­ing up­grades cur­rently avail­able to stop clas­sics get­ting too hot un­der the col­lar.


Up­grad­ing the cool­ing sys­tem by fit­ting an alu­minium ra­di­a­tor of­fers a larger cool­ing area over a stan­dard ra­di­a­tor. Spe­cial­ist sup­pli­ers are able to man­u­fac­ture cus­tom-made alu­minium

ra­di­a­tors and Rim­mer Broth­ers can sup­ply one suit­able to fit an MGB for £550.

Spe­cial­ist firms are able to re­fur­bish leak­ing brass ra­di­a­tors by sol­der­ing in a new core and its worth en­quir­ing if the num­ber of tubes in a re­place­ment core can be in­creased to aid cool­ing.

What­ever type of ra­di­a­tor is fit­ted to your clas­sic, make sure the pres­sure rat­ing of the cap is cor­rect for the car’s cool­ing sys­tem, es­pe­cially if a high per­for­mance ra­di­a­tor has been fit­ted rather than a stan­dard one.


These work on the same prin­ci­ple as a ra­di­a­tor by forc­ing cold air through tiny pipes filled with hot lu­bri­cat­ing oil di­verted off the en­gine’s main oil gallery. Usu­ally fit­ted along­side the car’s coolant ra­di­a­tor, oil cool­ers can of­ten be too ef­fi­cient in very cold weather and may have to be blanked off.

Per­for­mance cars fit­ted with a tur­bocharger may ben­e­fit by hav­ing a larger or even a wa­ter-cooled in­ter­cooler fit­ted.


Moulded rub­ber ra­di­a­tor and heater hoses can de­grade over time and find­ing re­place­ments for some clas­sics can be al­most im­pos­si­ble. Thank­fully, spe­cial­ists such as Clas­sic Sil­i­cone Hoses (01530 230971) are able to sup­ply hose kits for a large range of clas­sic ve­hi­cles and hoses are avail­able in var­i­ous colours, in­clud­ing satin black.

Sil­i­cone hoses are more hard wear­ing than cheaper rub­ber equiv­a­lents (which may not be avail­able any longer) and when fit­ting a set of re­place­ment sil­i­con hoses, it’s al­ways a good idea to in­vest in a new set of good qual­ity worm-style stain­less steel screw clips.


In­creas­ing the size of a ra­di­a­tor’s core is an ef­fi­cient way to re­duce the coolant’s heat load. How­ever, it may be nec­es­sary to fit an uprated wa­ter pump to avoid any cav­i­ta­tion (bub­bling) in the coolant at high revs. Re­plac­ing a me­chan­i­cal wa­ter pump with a high flow ca­pac­ity elec­tri­cally driven unit has the ad­van­tage of run­ning at a speed in­de­pen­dent to the en­gine. An elec­tric pump can also be set to run con­stantly or through a con­troller to make it switch on at a set tem­per­a­ture.


The ideal op­er­at­ing tem­per­a­ture for an in­ter­nal com­bus­tion en­gine to work at its max­i­mum ef­fi­ciency is be­tween 92 and 95°C . Fit­ting a ther­mo­stat that opens at a dif­fer­ent tem­per­a­ture to the one in­stalled will make the car run hot­ter or cooler to suit the am­bi­ent tem­per­a­ture and op­er­at­ing con­di­tions. Swap­ping a ther­mo­stat for one that opens slightly ear­lier is an easy fix to make and en­gine run cooler, es­pe­cially in very hot weather.


This spe­cial for­mu­la­tion of fluid con­tains no oxy­gen or min­er­als and used prop­erly wa­ter­less coolant, which has a boil­ing point of 180°C, helps elim­i­nate cor­ro­sion. The abil­ity to work at such high tem­per­a­ture pre­vents

hot spots of steam de­vel­op­ing in high per­for­mance en­gines. An­other ben­e­fit for us­ing wa­ter­less coolant is that it al­lows the cool­ing sys­tem to run at a lower pres­sure, which in turn re­duces the stress on com­po­nents.

Wa­ter­less coolants also con­tain a spe­cial blend of anti-freeze and can be used in tem­per­a­tures as low as - 40°C. When swap­ping over to wa­ter­less coolant, a spe­cial fluid has to be used to ‘clean’ the sys­tem out and neu­tralise any re­main­ing H O, which makes it 2 best to switch over to wa­ter­less coolant dur­ing a ma­jor en­gine re­build. For more in­for­ma­tion about the long-term ben­e­fits of us­ing wa­ter­less coolants, visit www.even­


Not so much an up­grade, but the con­cen­tra­tion of the coolant in a car’s ra­di­a­tor should be pe­ri­od­i­cally checked with a hy­drom­e­ter to en­sure the ra­tio of wa­ter (prefer­ably de-ionised) and anti-freeze is main­tained at the cor­rect per­cent­age.

Mod­ern anti-freeze is made up of 96 per cent eth­yl­ene gly­col and four per cent cor­ro­sion in­hibitor. When top­ping up a cool­ing sys­tem, it’s im­por­tant to know what type of anti-freeze to use. Cars built be­fore 1998 usu­ally re­quire a sil­i­cate-free anti-freeze, while those built af­ter that date re­quire a 50/50 coolant mix us­ing ‘organic acid tech­nol­ogy’, or OAT for short. OAT anti-freeze is usu­ally orange in colour, while the sil­i­cate-free coolant suit­able for clas­sic en­gines is usu­ally red or green.


De­spite be­ing matched to a de­cent sized ra­di­a­tor, the fan suck­ing cold air into the en­gine bay may not be able to cope in very hot weather. Vis­cous cou­pled ther­mo­static fans can break down and some own­ers even bolt the mech­a­nism up so they work con­tin­u­ously. This de­feats the ob­ject of hav­ing a fan that only runs when it’s needed and a worth­while up­grade is to fit a ther­mo­stat­i­cally con­trolled elec­tric fan. These can be ad­justed to op­er­ate at a range of dif­fer­ent tem­per­a­tures and are rel­a­tively easy for a DIY owner to fit. Revotec (01491 824424) stock a large range of kits suit­able for clas­sic cars, and can be fit­ted along with grilles and ducts to help keep the en­gine bay cool.


A lot of clas­sics didn’t have a coolant tem­per­a­ture gauge as stan­dard and in­stalling an af­ter­mar­ket gauge will pro­vide in­for­ma­tion in ad­vance if things start to get too hot un­der the bon­net. Ex­tra gauges to show wa­ter and oil tem­per­a­ture can be in­stalled in a neat bin­na­cle un­der the dash and are rel­a­tively easy to plumb in and wire up. Rather than add an ex­tra dial to a clas­sic’s in­te­rior, some own­ers may pre­fer to wire up an un­der­bon­net tem­per­a­ture sen­sor that can be set to sound a warn­ing buzzer or a lamp if the coolant tem­per­a­ture starts to head north.


Adding a small amount of pro­pri­etary coolant ad­di­tive such as Wa­ter Wet­ter to the anti-freeze mix is a chem­i­cal way to help re­duce the tem­per­a­ture of the coolant by up to 20°C. Wa­ter Wet­ter has bet­ter heat trans­fer prop­er­ties than off-the shelf gly­col-based anti-freeze and adding a small dose will also help to re­duce the for­ma­tion of rust and cor­ro­sion in the ra­di­a­tor and as­so­ci­ated wa­ter­ways.


A num­ber of clas­sics, such as the V8-pow­ered Tri­umph Stag, gained an un­en­vi­able rep­u­ta­tion for over­heat­ing. Over the years spe­cial­ist sup­pli­ers have de­vel­oped a wide range of up­grades and im­prove­ments to help elim­i­nate the prob­lems that caused the Stag’s V8 en­gine to brew up. How­ever, be­fore de­cid­ing to dras­ti­cally up­grade a clas­sic cool­ing sys­tem, it’s a good idea to do a bit of sim­ple main­te­nance first. All the old coolant should be drained out and the sys­tem back flushed to re­move any muck and sed­i­ment from the wa­ter­ways to see if this im­proves mat­ters.

Cars fit­ting with an au­to­matic trans­mis­sion may have a heat ex­changer built in­side the ra­di­a­tor to cool the trans­mis­sion fluid. Leaks will al­low anti-freeze to con­tam­i­nate the trans­mis­sion fluid, so con­sider fit­ting a sep­a­rate oil cooler for the auto box. Keep­ing a car’s cool­ing sys­tem in good or­der is the key and if the tem­per­a­ture gauge starts to climb there are plenty of up­grades avail­able to help a hot en­gine main­tain its cool.

Ther­mo­static con­trolled elec­tric fans can be po­si­tioned to ei­ther suck or blow in­com­ing air through the ra­di­a­tor.

Bon­net vents and lou­vres help keep tem­per­a­tures in the en­gine bay down but can be very ex­pen­sive to retro­fit.

Wa­ter­less coolant doesn’t con­tain any oxy­gen or min­er­als and has a much higher boil­ing point than nor­mal coolant.

A cold air feed di­rect to the carbs will aid en­gine ef­fi­ciency. Al­loy ra­di­a­tors are able to dis­perse ex­tra heat quickly.

Sil­i­cone hose kits usu­ally in­clude new stain­less steel clips.

An al­loy header tank can be much big­ger than the orig­i­nal.

Per­for­mance en­gines re­quire a huge amount of cool­ing and fit­ting ex­tra elec­tric fans will stop boil ups on the track.

When adding anti-freeze, make sure it’s the cor­rect type.

The Stag’s V8 was no­to­ri­ous for over­heat­ing but fit­ting a larger ra­di­a­tor is one way to keep the tem­per­a­ture down.

Find­ing space to fit uprated cool­ing parts can be an is­sue.

Sil­i­cone hoses are avail­able in a se­lec­tion of bright colours.

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