Race 8v Engine Overheating Ridiculously Quick

[wardy18 33 1 Cars]

Hi all

 

Having just done a speed event today (1/4 mile sprint) with many problems i managed to get over and finally gettin a few runs in i found the engine was overheating dramatically and extremely quickly

 

The engine has not had the ignition timing set yet and the twin 45s definitely need setting up as im sure she's running very richIm running a standard fan, slightly cut shaved to fit with fibreglass bumper and a standard rad, the engine is a standard bottom end XU9 with a XU9 head at a CR Ratio of about 10.9 from a heavy head skim, also running a strong rally Catcam and as said above Twin 45 Webers also with a re-curved Dizzy by H&H, its kickin out an immense amount of power but is overheating with minutes od simple idle, i am unable to let it idle while lining up waiting for my run at events and its a serious problem for me, im running a standard Thermostat, i think 82 deg and seriously considering running without one, water pump is fine and system has been flushed a few times

 

WHY IS SHE OVERHEATIN SO QUICKLY?!

 

Is it maybe cause the engine not set up with the ignition timing so making it run hotter, maybe detontating, the engine and exhaust is so loud and with the carbs not set up right its impossible to run in 5th gear at low rpm and hear for pinking

 

ANY IDEAS WELCOME

 

thanx

 

Here's a run you can see and hear her!!

Sounds so sweet

 

Edited April 19, 2008 by wardy18

[Tom Fenton 1,526]

I would look at a sniffer test to check for HG problems, it should not overheat that quickly. Does it use any water?

[wardy18 33 1 Cars]

"the sniffer" is that that thing u stick in the header tank and pump it, if it changes colour your headgaskets gone, if so i havent got one of them, if teh headgasket was gone surely there would be water in the oil so just check the dipstick?!

[Tom Fenton 1,526]

Yes it is, and not neccesarily.

[Rom 0]

Is the rad or heater matrix blocked ? If its ever had 'rad seal' or similar that can lead to blockages etc.

 

For it to overheat that fast there must not be proper coolant flow..or something else quite serious. A major air lock could cause similar. Even at idle without a fan it should take quite a while before its generating too much heat to cope with.

When driven is it still overheating ? You say you cant let it idle..is it ok at speed ?

 

Being out of tune etc wouldnt make it heat up that quick imo. And not to the extent where the car cant cope. Does the fan cut in and out ?

Do the heaters come through hot ?

Even with a head hasket gone, id expect the system to be pressurising also. Or signs of contamination in the oil / water.

 

Try idlein it with no stat in it.

[wardy18 33 1 Cars]

I may have found the problem, i ran it up before and the pipe from the header tank to the back of teh block and the pipe from the water housing to the back of the block was warm and also the small one from the water housing to the header tank were warm but the pipe leading to the bottom of the rad was cold ish and the pipe from the top of the rad to the water housing was cold

 

so im thinkin that the rad is actually blocked which would also explain why i found no difference when i refitted a standard 205 fan instead of the tiny little after market fans that were fitted

 

the car has no heater matrix as its purely a race 205 so has no heaters/dash etc etc

 

so first of all i need to remove the rad and flush it throu with a hose and see what happens

[brianthemagical 1]

Sounds like the stat. is the rad warm?

[wardy18 33 1 Cars]

no the rad was cold too

 

im gonna actually remove the stat and run without one i think

 

so if the stat wasnt workin properly i suppose that would stop water circulating throu the rad as it would all be backed up, could also explain my problem, well then before i go to all the effort of removin the rad ill just take out the stat and run her up and see if the rad gets warm and the temp stays down!!

 

Thanx i hadnt thought of the stat

[Rom 0]

You must have missed it in my wall of text

 

At least youll know for sure that coolant is getting to the rad that way. Then its down to wheter the rad is blocked or not

[wardy18 33 1 Cars]

must have sorry

 

well i removed the thermostat last nite and its workin fine in the old jug of boiling water, then pulled the rad out and flushed it throu with a hose, wasnt blocked!!

 

one hose that was blocked however was the little overflow one from the top left of the rad back up to the header tank, so anyway im gonna put it all back together and maybe flush thropu some other hoses then see how hot it gets and if it can maintain a good temp with the fan on as the fan at the moment is makin apsolutely no difference when its on at the moment!!

Edited April 22, 2008 by wardy18

[Tom Fenton 1,526]

That small hose allows the system to self bleed, if that was blocked then you were most probably getting air locks in the system.

[wardy18 33 1 Cars]

could be my problem then, i took it off and blew throu it and it was blocked then all of a sudden its splutered and then unblocked, so yeh thats what i was thinkin aswel, as you fill the system the water woukld push the air out of this pipe and so completely fill the rad!!

 

well ill flush throu the rest of teh pipes and leave the thermo out and see how i go!!

 

what is the normal operating temp of the engine!?

[tom_m 0]

around 85-90 is about right with a decent quality rad and working stat.

[leon 1.9 0]

I would think its going to be airlocked, when ever you refill the system you should bleed the air off. Trouble is, I can't remember for the life of me where the 205s should be bled from. Is there a screwed plug near the top of the rad?

 

I had a Fiat Punto (ooh the shame) that did the same after I changed the 'stat (which was stuck so the car wasn't warming up), run the car at idle for two minutes and the temp would rocket, finally got it bled and it was fine.

 

What have you done with the heater matrix supply and return pipes, if the matrix is gone? Could air be stopping flow because of that?

[wardy18 33 1 Cars]

they bleed through a allen key bolt in the water housing just by the thermostat!!so just so that i get this right i have draw a very bad diagram of my cooling system, as you will see theres no heater matrix, so am i right in thinking that before the thermostat is open the water flows round the Green Coloured cycle (not sure which direction) then when the Thermostat opens the red section is included in the cycle?!im not sure which pipe the heater matrix normally runs off, is it the pipe from the sidfe of the water housing then back into the back of the block, if so then from the diagram you'll see how it runs now!!does it also matter which pipe you connect the main pipe from the header tank and the pipe from the water housing into the back of the block, there's two ports side by side in the back of the block, does it matter which pipe goes on which?!pic

[wardy18 33 1 Cars]

ok system completely flushed throu and stat removed so now just gonna run her up and see if i can maintain a temperature or if it carries on rocketing out of control

[wardy18 33 1 Cars]

great result, filled her back up yesterday and ran her up to 90deg, switch the fan on and can came back to 70-75deg within a minute and it held that temp (until i revved it obviously)

 

very happy with it now