Overheating!!

[flipscobra]

Jets all you have to do is flip a switch an your fan will go off, so how you get your fans will run all the time. The only way they will run all the time is if its running hot, If I wait for the stupid themstat to cut on mine would be running hotter than I want it to get, an run a 160 thermasat, an drill a few extra holes in the face

[vettestr]

I hate hot engines !!!

Verify you have at least 30* ignition timing at 2700 RPM.. this is a min. not a target

verify your crank pulley is larger than water pump pulley by a min of 15 %

V you have a working 180* T-stat and it is not being bypassed (rad cool until t-stat opens on start up)

I place fan sensor in rad to turn on fans if temp above 180* (this allows fans to cycle)

I have a manual fans on - dash switch so can turn on in traffic .... period

air / fuel ratio a little fat helps cool engine. lean mix runs hotter check what you have

you never specified when or how it was overheating... IE. only in traffic but cools at freeway speed or only when on the freeway or stop n go starts overheating and won't recover once she starts to get hot or ??????? GOOD LUCK be patient

[Mohuska]

First, thanks for all the advice. This one of the things I really like about this forum is that there are so many with experience on such things. While I have been working on cars for many years, it is good to get feedback and new ideas.

To add a little more detail, my Cobra will get up to 180 deg within a couple of minutes of starting. The fuel/air ratio is 13.7 at idle (14.7 would be stoicimetric), so it does run a bit rich. In fact, even cruisin down the road I smell overrich fumes (not to mention that my clothes smell like unburned gas when I stop).

My engine is a 460 that was punched out to a 522 with TWM stacks and a FAST ECU controlling everything. As far as running, it is a beast! Seems to have incredible response and more than enough grunt in all 5 gears.

Regarding overheating, it will go up to 225+ shortly after I get on the road and will vary between 200 and 240. If I come to a stop with it idling (after running hard) the temp will drop very quickly to 190-200. As I said before, the fans come on at 195. If I cruise about 35 down the street, it will go down to 200 and mostly stay there. If I hit it hard off the line, it will jump to 200-230 and then come down when I stop again.

I think that getting a coolant bleed valve will be the first step and then I will pressure test the system (thanks Hersh). I will run it several times and bleed, burp and refill (thanks Tom).

I don't think I need to change the fan settings. Most BB motors like mine generally run at 190+ (even my Jeep GC runs typically at 190+)

Thanks again to everyone. I will post on this after I try some fixes. In the meanwhile, I still appreciate any ideas.

Cheers,

Mike

[Tom Wells]

Mike,

One more thought after your further description: it sounds like you have been reading a voltmeter instead of a temp gauge

Is the temp gauge electrical? If so, could it be responding to alternator voltage? When you spin the engine faster, the voltage may rise, and the gauge may indicate higher temp which may or may not be the case.

Maybe Hersh's suggestion of using an infrared non-contact temp gauge on it would be a good diagnostic?

Just another bit of confusion for the pile...

If it's mechanical, please ignore the preceding!

Tom

[Mohuska]

Tom,

Thanks for the insight. Is there a way to determine that the gauge could be fluxuating based on voltage?

I do have an infrared temp sensor already. I will check out entry and exit temps no matter what.

Mike

[mdross1]

Assuming you have enough cooling capacity,you have some great advice to work with.My 460 high effeciency radiator made of copper was sized by a 30 yr veteran in the radiator business.At first made me nervous until system was completely burped of air.It goes to 190 degrees quite fast then stays there.On hot days and in traffic the fan runs contantly,only shuts off when cruising for a while no load.

[kitcarbp]

Food for thought.
If your surge tank has the 5/8 or 3/4 "fill line" entering into the top of the low pressure side rad tank, its still not as good as it being connected to the bottom of the low pres. side tank or "Tee'd" into the suction (low pressure) hose leading to the water pump.

Why ? As you fill the system via the chrome surge tank where pressure cap is, in your configuration, the coolant will enter into the top of the low side tank and as it fills the rad core tubes will trap some air making it more timing consuming to burp the system after a few heat cycles. Not impossible, just more troublesome.

If the "fill line" is connected to the bottom of the low pres side tank or lower rad hose, during filling, the liquid will travel into engine block (via lower rad hose) and into rad and then force the air up and out from the bottom of rad core upward (via the small air bleed line at top of low side tank on my set-up). likewise as coolant travels into the engine block from the bottom, it forces the air up and out of the therm housing bleed valve.

Ahh the fun of custom cooling systems !

[Mohuska]

Bill,

That makes complete sense. I will look into that. Do you know of anyone who sells the bottom hose "T" fittings that aren't plastic??

Thanks.