Hi Folks,
My name is peter and i have had my GTM Rossa mark 2 for 9 years!
i live in south manchester. i never see any other GTMs but i use mine every day.
sadly its very scruffy.

It has a 1310 engine , kent 600 cam ( like a cross between a 266 and a 276 cam) ,
got high comp metro pistons and 22.5cc combustion chambers and copper gasket.
so im at about 9.75 : 1 compression ratio. 1.4 inlet valves 1.1 lead free exhausts.
NGK bp7ES spark plugs

Single hif44 su, mg metro inlet manifold , 1.6 1986 ford orion exhaust back box (only £45!).
the orion exhaust box pretty much fits where the special stainless steel box fitted.
i had to get rid of the stainless steel box as i rightly suspected it was blocked and it was
so well made i could not cut into it to unblock it!!
close ratio cooper s box, 3.4 final drive .

ive fitted a 2 litre sherpa van radiator (yes really!) its the same width as a metro radiator
but much deeper. the top of the radiator sits where the metro radiator did
the bottom much further back - so its slanted. ive got a 300 watt volkswagen fan sucking air through it.
the fan is on a switch that i control.


i have two requests for information:

1. in town overheating has ALWAYS been a problem. and still is.
if you have a town driven 1275 GTM rossa and it doesnt overheat please tell me your spec!
any info no matter how trivial would be welcome
im thinking of cutting a MUCH bigger hole in the front to let air in through the bodywork
am i mad?

2. between 40mph and 80 overheating is NOT a problem.
when im in Germany and doing 90 plus it gets hot - an oil cooler sounds good for this situation
has anyone fitted one and where will it go? surely not the hot engine bay!


thank you for your trouble!

best wishes

Peter

ps here is some more info:

when on the motorway if you wind the window down halfway engine temperature drops markedly, it does.
ive fitted metal springs where the rubber cones went and its a good mod - much less harsh.
no major mods - just remove the rubber cones and put the chunky springs in.
ive removed the bimetallic nonsense from the HIF carb - now no lean out when the carb gets hot - another worthwhile mod
but you need to make up your own metal replacement.
valve clearance for my cam is 16 thou with normal rockers. im running 18 thou it gives NOTICEABLY better torque at very low revs. only worth doing if you have a hot cam and dont open up the clearance too much or you will break your cam very quickly
thanks again for your time.

Overheating at slow speeds or in town could be your water pump not pushing enough water through the rad at low engine speeds.
An electric water pump may sort that out.
Was your radiator new? A partially blocked rad could cause both your problems.
Overheating at high speeds could well be your oil rather than your water. What does your oil pressure gauge say?
An oil cooler is not a bad idea anyway.
You could front mount a normal air/oil cooler or an easier, though more expensive option, is to fit a laminova water/oil cooler.




They can be mounted anywhere and need no external airflow.
You do need to sort the cooling first though as it uses the engine cooling system to cool the oil too.

What size are your front to rear coolant pipes? Too small = not enough flow, too big = not enough speed of flow.
Mine are approx 1.25" and work fine with 120ish bhp - allegedly.
You can get a lamina type water to oil cooler off a scrap Mk1 MR2 for pennies.

As for opening your window to cool the engine, that could be a problem with airflow, that the open window helps with, or your front/rear pipes and heater matrix start helping more with the heat dissipation.

You haven't got any extra spoilers etc on it have you?

Thank you gents.

Electric water pump is something i never thought of so thank you for that.
and thanks for the picture.
and yes it could well be that my normal water pump just isnt shifting enough water
it idles at 800 rpm and i have a small diameter pump pully so in theory it SHOULD
be OK but you never know.
ive got all sorts of gauges on her but not oil temp.

I didnt build my Rossa but i notice the big fat rubber hoses get sized down a bit
before going through the tunnel as metal pipes. i will look at their diameter.
if they are too small its gonna be a big job to change them ! yuck!
thank you for that info about pipes.
the sherpa radiator was brand new four years ago and i do regularly flush it.
maybe i should get a new one.
but even when it was new cooling was VERY marginal

Nelly (thats her name) is running REALLY well for the first time with all issues sorted
and if i can sort the overheating
then i will tidy her up and not be ashamed to come to events!

will keep you posted as to my discoveries


thanks again

peter

If you search "electric water pump" on ebay it will come up with mercedes and vauxhall? aux water pumps which feed their respective heaters. One of these as a booster might help instead of forking out for a Davis Craig pump.

Your front to rear pipes are more likely to be too big than too small. A lot of people over-estimate the pipe size, the flow slows right down and doesn't cool quickly enough.

Do you have a bleed-off on the top of your rad? You might have an air lock.

It's almost definitely a water flow problem as opposed to air flow.

I don't know the Rossa very well but I'd put money on it being a air lock some where

Hmm my post i wrote at lunch never made it by th elooks of things?

Are you sure the water is circulating to the rad fully? when I first got a Coupe with a 998 with how it was plumbed it preferred to pump its water through the metro header tank than through the rad at tick over. plus it was not high enough really to get the air out really well.

First thing I did was junk the header tank and fit in an inline rad cap adaptor in the top hose and mounted this as high as possible, this fixed it and never had issues with air locks, This has only just recently been replaced with a shiney swirl pot style one due to a weld becoming porus and this seems to be working really well.

on the size of hoses I have 1 inch cooling a 1800!

West

I didn't build my rossa, but it has an oil cooler fitted at the front, opposite where the battery is, it does mean that there are long runs of oil cooler pipe and I'd probably go with a laminova type solution, if I was re-doing it.

My cooling seems good, again, I'd suggest an air lock?

Regards,

Allen

Could it be the small pulley makes the water pump turn too fast at higher RPM and causes cavitation ??

thanks for all the posts guys.

its great to get input - really appreciated.
its got me enthusistic about sorting this!

OK some stuff i DO know.
I HAD to use the small pulley or else town overheating got worse.
its possible that the very high speed overheating IS cavitation.
but town driving has to come first!

i can put my hand all over the huge radiator and its definitely ALL
getting warm. I definitely DONT have an airlock. water flow SEEMS to be good.

three weeks ago i had the cylinder head off, cleaned it up and dipped it overnight
in deox c rust remover. this did remove rust from the head's water ways.
after re-assembly car seemed to get very hot as usual.

after checking that the deox c was not going to eat into my rubber pipes, brass radiator or aluminium water pump i put some solution IN the cooling water for three hours then flushed it out. seemed to have no effect. but the car has been getting steadily BETTER with less overheating. deox c completely dissolves rust and i think i left some deox c in and it has been cleaning out the waterways over the last week or so. last night i was 1 hour in traffic from Crumpsall to here and no sign of overheating. This is really good im dead chuffed.

ive been trying water wetter and find it really helps when the engine gets really hot
it seems to stop it actually boiling - ie keeps it liquid rather than steam . but doesnt
keep the engine any cooler in normal use

the block was chemically dipped 2 years ago and the head deox c dipped then also.
but overheating has been an issue since then. im wondering about all this.maybe the block was still rusty somewhere. or some rusty lump caught in the cooling system that the deox c has dissolved or partially dissolved?

so to sum up " its looking good and i have not yet tried an electric pump or oil cooler! good good"

with a gtm rossa i think everything HAS to be spot on or your car will overheat in traffic!

regards

peter

How restrictive is the grill you have in front of the rad?

Given the air comes out under the car. maybe with the rad angled that way air is just flowing over the surface rather than through it.

A front splitter might increase the pressure in front of the grill at speed, reduce it under the car, and improve flow through the rad.

Have you fitted a lower temperature thermostat?

Have you drilled the thermostat and blocked the troublesome bypass hose?

Is it the high capacity water pump?

Have you wrapped the exhaust manifold?

Opening the window is an interesting one. I am aware that as standard there is no provision for air to escape from the back of the cabin flow through the fresh air vents is poor unless you open a window, but not sure how this would affect the cooling.

74 degree thermostat. lots of holes drilled in it! no bypass . high cap pump.
so thats all OK.

i think you posted at the same time as my last post - its looking a lot better since i put
deox C IN the water system.

yes - i think i need to baffle the huge radiator better as at high speed the air can get round it.

thanks for the post.

since nelly really is running well and overheating is the ONLY issue left , ive gone mad.
thank you for all the posts.

decided that a huge sherpa van radiator that doesnt fit snugly is bad.
Something more snugly fitting is probably good.

ive got a new skoda felicia (1.3) radiator have built a nice aluminium surround for it
and got a low profile fan from a volkwagen polo.
it all goes VERY snuggly under the bonnet - no gaps at all after fiddlin aboot.
the skoda rad is definitely a good size for nelly

then removed the registration plate - sprayed the reg directly onto the body and . . . .

. .

can you guess what?

drilled holes in the lettering and then went back over the lettering with little
black paint brush. the letters are more hole than letters if you get my drift.
but you cannot tell unless you are 2 feet from the reg.
removed the silly chicken wire grill from the main ventilation hole.

there is a now A LOT more airflow possible.

hopefully the wonderful summer weather we all deserve will now not be a problem for little nelly.
we shall see . . . .

was out today for the first time with the skoda felicia rad, and holes in numberplate
in manchester traffic and - much better!

hooray!

it does look like the smaller radiator properly baffled in with holes in the numberplate
and the electric fan are all working really well for town driving!



marvelous