Cam break in overheating issue/ airlock?

[johnny46]

Hi all

I am trying to break the cam in on my engine and unfortunately the engine water temp is shooting through the roof, I managed to get 4 minutes into a 1500rpm break in on the cam and the temp got too high and I had to knock it off.

The top hose was Cold so I removed the stat in case this wasn't opening and tried again but again the problem arose, the top hose is now hot and full of pressure I'm guessing I have an airlock and its preventing the proper circulation??

The rad cap is full of pressure and wanting to spurt water everywhere, why hasn't it gone up to the rad cap and into the overflow?

I filled the system initially at the rad cap with the rear hose of and once it was there I put the hose on and continued till it was at the top,

Also I have no fan shroud so it won't be cooling as Good as it should, will I be able to run the car at 1500rpm for 10 mins and keep a safe temp??
If the above is right how to I solve the airlock?

Thanks in advance people

Johnny

[bhm1712]

If it is an airlock the best way to do it is to run the engine with the radiator cap off to allow the bubbles to "burp" out of the system but unfortunately this will not help with the cam break in! you don't want to ruin the cam faffing around with cooling issues!!

if there is pressure in the system not being vented by the rad cap - is the cap faulty?

try running it with the cap off and see if you can see signs of air coming to the top and venting.

[johnny46]

I remember at first when it was running after a few minutes it was burping out of the rad cap as I had left it of, but it was burping and chucking water out so I put the cap on

[bhm1712]

I usually drop the level to about 3 inches below the filler neck when burping the system. If it's chucking out water at the rate which it sounds like your describing it sounds a bit extreme....do the bubbles get worse when you Rev up?

[johnny46]

To be fair I had it at the top so not surprised it was burping it out, I will drop it then and try again, didn't rev just had it at constant 1500rpm for the break in then knocked it off. Would the engine stay at a safe temp if the cooling system is correct and without a shroud?

[bhm1712]

I know of people who don't run with a fan shroud and whilst it's not best practice and dramatically alters the flow of air through the radiator they must be able to cope. Having said that I would never run without a shroud. Maybe get some big fans in front of the car if possible? 1500 rpm at a standstill is not a routine thing so it may well throw up some overheating issues without a shroud. Have you checked the fans coupling is working ok?

[johnny46]

I haven't bled the system properly there's one prob I need to sort, fan coupling? It's connected and spinning with the engine? I will search tomo for some big industrial fans and have them on it when I next kick her up. Thanks for ya help so far dude

[bhm1712]

The fan will be driven from the water pump via a viscous coupling. With the engine off you should be able to turn the fan over and feel resistance but the water pump pulley will stay static. The viscous coupling alters how much drive is applied to the fan depending on engine speed and temperature. If it's worn out the fan will basically free wheel and just spin with no real effort and draw little air through. When you first start the engine if you Rev to about 2000 you should hear and feel the fan working and then around 10 seconds later the fan will slow down and the noise will alter until the engine starts to warm through and then it will start getting faster and pulling more air through again.

Simple test is to roll up a newspaper and make it quite firm, with the engine at temp or getting towards overheat you put the rolled up newspaper end into the path of the fan. If the fan stops the coupling is worn out. If the newspaper is shredded to within an inch of its life chances are the coupling is fine. Hold the paper very firmly!!

Having said all the above, some earlier pontiacs and modified ones have had the coupling removed and changed to direct drive.

If it has something akin to the following picture directly behind the fan blade hub then it's got a viscous coupling

[johnny46]

Yes that's behind the fan, it looks like it runs pretty fast I wouldn't want my hand there lol will try the paper held firmly it will have a shroud on it but only when it goes to robin in a few weeks

[Big Chief]

Johnny,
Best to give me a ring so i can talk through what you have done at the beginning.

[johnny46]

What's your number dude ?

[johnny46]

Ah Robin I will ring you shortly