Overheating?
 

Hi all,

As some you may know i finally bought my first cobra a month or so ago. Unfortunately after a few short drives on warm days I found the car was overheating. :CRY: I knew there was an ebay water and 16 inch thermo fan in the car. This didn't fill me with confidence thats for sure.

First on the agenda was get the radiator looked at sure enough if was about 80% blocked. While I was at it one of the boys from the club suggested I fit a Davies Craig 16" thermo fan and put in an Edlebrock flow water pump. The guy from the radiator shop suggested a high flow thermostat as well. So the cooling system is now sorted.

There is a suggestion that a head gasket maybe on backwards checked that and found that the tag that should be at the front of the block on the passenger side is actually at the back :eek:. I was going to pull the heads and check but basically didn't have the balls. I also spoke to a few mechanics and all agreed that if the head gasket was backwards I wouldn't have go it home from Bendigo were I bought it. Also it would over heat very quickly if the gasket was backwards.

So with all of this done yesterday was D day. I fired it up (massive grin), as usual. I ran it at idle in the shed for about 1/2 hour letting all the air out of the cooling system cap on off we go. First test drive seemed to perform perfectly although not a very hot day in Melbourne yesturday.

Next sumoned up the courage to take it for a big drive basically into the city and down Beach Rd. All was perfect until on the home run, I hit a few traffic lights in a row and the dreaded South Rd train line. 2 trains later as the temp gauge started 2 nudge 210 F my heart rate was starting to increase not in a good way. Once we got going again the gauge quickly returned to were it had been the whole trip nailed to zero on 180 F.

I guess after all this I am just after thoughts as to whether I am just being paranoid about the gauge getting to 210 or do I still have a problem e.g dread head gasket or something else.

Any thoughts

Andrew

Hey Andrew, Those temps look ok (to me). I know I have a different engine but my LS1 moves between 80 (normal) and 95-100 (Hot or at lights etc). I've driven it on track and pretty hot (40 C) days and these seem to work ok.

I suppose it depends on what temp your thermostat opens etc.

Cheers

Gregg

mine runs about 175f on the hwy and around 195f to 200f at the lights.
On a 40c day I have heard the twin thermos roaring and it was about 205f

210F is only 99C. If your system is pressurised properly (no leaks) and has the proper ratio of coolant / water, then it will not boil until at least 105+, more likely 115+ with good coolant and ratio. Sounds ok to me.

I run LS1 with 2 fans, the front fans I manually turn on all the time (they look cool) and the main cooling fan is triggered to come on at 210f.
In traffic it comes on and when sitting at idle.

Make sure there is no air gap between your fan shroud and the radiator. If there is a gap there then air will pass through it rather than be sucked through the radiator, therefore decreasing the effect of your thermo fan. You can buy adhesive rubber of varying thicknesses from Clark rubber. This is perfect for sticking in any gaps between your fan and the radiator. These little 5% differences really add up...... Having said that my LS sits around the 200 - 210 mark in racing situations.

210°F is nothing - mine has a 180°F thermostat (starts to open at 180°F) and typically runs 180°-210°F on the open highway and 190°-220°F in traffic. It's worth noting I'm running a high-flow thermostat and the plate has two 3/16" / 5mm holes drilled in it to ensure full purging of air. Those additional holes do cause it to take a bit longer to warm up when ambient temperatures are cool - like this morning when it was 3°C on the run in to breakfast. Yikes.

BTW, the car hit 250°F in traffic a couple of weeks ago when the cooling system fan relay quit working and, while it spit a bit of coolant it did not 'boil over' - the result of a pressurized system running 60% ethylene glycol. The manual override switch on the dash made no difference as it just activates the relay. The single relay (from a C4 Corvette) has now been replaced with a pair of 40 amp relays wired in parallel - they share the load and either one alone is sufficient to handle the load, should one fail though, of course, that will never happen now that I have redundancy!

towmaster is on the money with the shroud on our race car i mucked around with electric fans of different brands and blade shapes after a great deal of frustration i build a new shroud thats got no air gaps threw away all the electric fans and went back to the factory steel blade fan car can do 40 laps on the dirt and never go over 190f works like a charm ..

Also a curved blade is more efficient than a blade that is straight from the centre to the shroud. I have a mate that was an engineer for Bell Helicopters told me that.....

Those temps seem good to me. Both of my engines were designed to make the most power at 220° and I have had to block air flow on cool days to get them up to 200° degrees as I could feel the loss of power at around 180°. It is normal after running on an open road and coming into stop and go traffic for any engine to have a heat surge and yours seems to be doing very well.

Ron

So how come helicoptor blades (and airplane props) are straight?

Hi all,

Thanks for your thoughts and input, looks like I am just being paranoid which is good I guess. I now really need to test it on a hot day in traffic that is the real test I guess. On the straight curved blade issue, the ebay fan had more blades and was curved the Davies Craig has less and they are straight. Don't really know what it all means but the Davies Craig fan certainly moves significantly more air than the ebay one (funny about that) and even dims the headlights and dash lights when turned on. Hmm may need a new alternator bugger. It will have to be a shinny chrome one more under bonnet bling :LOL:.

Cheers Andrew

Not all are. Depends on the requirement of the particular aircraft. Civil aviation is quite a conservative industry. Have a look at the turbine blades on a late model airliner, they will be generally be curved or sickle shaped.

Compound shapes require the use of hybrid construction using composites combined with exotic materials such as titanium.

Light aircraft such as a Cessna 172 don't see the benefit of exotic engineering so not worth the cost of development and certification.

Yep that's what I was gunna say......... lol

In essence that is what my mate told me..... I just couldn't remember the technical bits just the 'curved blades are more efficient' bit...

Many of the newer turboprops use curved or scimitar blades - apparently higher tip speeds see more benefit from it, which may explain why smaller aircraft (e.g. Cessna 172) are fitted with straight-bladed props.

https://en.wikipedia.org/wiki/Scimitar_propeller

"Curved" blades have more surface area and varied angle of attack from root to tip so therefore can move more air. The blades are shaped so as to not have the blade tip reach the speed of sound.

The main reason a helicopter blade can't be curved is they first require a coning angle. Second the centrifugal force of the heavy blade means it's trying to straighten out, so a curved blade would put to much stress on the blade. You can't lift a helicopter by the blades if they were stationary, you can then imaging the force of them straightening out to be able to support a helicopter.
I tried several fans, 2 davie craig fans drew around 18 amps and the air flow was half of a single genuine commodore drum type electric fan drawing around 10 amps in a shroud, and quieter. Having the blades staggered makes it quieter also. The circular type fan roar because the blade width is so narrow, and have to many blades.
JD

The diameter of a fan blade, driven via engine or electric motor , that is mounted to cool a radiator, is such that it's small diameter is small enough that it will not reach the speed of sound.

A blade tip reaching the speed of sound will lose performance. however we do not have to worry at the speeds we turn our cooling fans.

OK, so to get back on topic, you know your head gasket is backwards, but because a thermometer mounted somewhere completely different tells you a low temp you feel OK.

Except that a Windsor gasket mounted backwards would stop all the flow through one of your heads.

So apart from the fact that the heads are the hottest part of the engine, everyone here says the thermometer sitting miles away which isn't getting any hot water because you don't have any flow through one of the hot bits is fine.

I reckon a head gasket it cheap compared to blowing something more seriously. Check it properly, know for sure.

Treeve

Here goes my 2 cents. Hi volume water pump, drill two holes in thermostat and the fan shroud has a good seal with large cfm fan. I suffered through overheat issues for a long time. When the engine was rebuilt I had the shop drill and tapped holes in the intake manifold across the firewall end (used marine grade fittings and line) with a line going forward to water heater point. I have hit two hundred but was running high rpms for awhile. Immediately goes back to 180-185. In Arizona at 110 no problems. Stop and go non issue.