Hello All,

I have a 69 shark running a 496ci. It has brand new aluminum rad and a Vintage Air serpentine belt setup which uses a reverse flow water pump.
It also has a mechanical flex fan bolted directly to the water pump studs (no fan clutch). Right now there is no thermostat in the car. After running the car at idle in 90 degree temps yesterday the gauge went up to about 195. I shut it down as I didn't want it to get any hotter.

Does a reverse flow water pump not cool an old school big block properly? I have run 69 Chevelle 454ci w/copper rad in 100degree temps with no thermostat and the engine temp never got over 160. I normally run a 180 therm in both cars. I've never seen a motor get this hot with no stat in it.

I'm pretty sure there's no air pockets. When it reached, 190 fluid started dumping out the overflow hose as well.

Any suggestions would be greatly appreciated.

 

I was always under the impression that running with no thermostat causes the fluid to pass too quicky through the radiator preventing proper heat transfer. Even without a thermostat there is supposed to be a restrictor plate, a thermostat with no guts, sitting in the housing.

 

You have an air pocket or some kind of restriction in the system. Could it be that the reverse flow pump is sucking down the upper radiator hose? (do you have a 'standard' upper rad hose or one made for suction support?)

 

You have either a weak rad cap or have overfilled the system. Is the fan shroud and all the seals in place?

195 is not hot. Many later Corvettes have that as the MINIMUM operating temp. 230-245 is hot.

Oh, and put in a thermostat. It cannot and will not hurt anything.

 

Is the water pump reverse flow, or reverse rotation?

 

Do you have a fan that is designed to work spinning counter clockwise?

 

All the seals are new and in place. I will try it with a 180 t-stat and a 160 t-stat. It has a cool-flex upper hose and a stock lower hose with the spring in it.

I guess my main question is does a reverse flow pump with a mechanical fan not cool as well as a standard rotation pump?

Here's my thoughts: with a standard rotation pump it pulls water from the bottom of the rad (usually cooler than the top of the rad) into the block when the t-stats opens. If running a reverse pump, when the stat opens the hotter upper rad water will flow into the block and down back into the bottom of the rad. The cooling efficiency seems it would be off or am I smoking something?

 

Good point - it is reverse rotation, not reverse flow - my bad.

 

Yes.

 

Based on you description of the problem, I have 3 scenarios in my mind regarding your problem :
1- If your water pump is rotating counter-clockwise, and a mechanical fan is hooked to it, then you're basically "pushing" air into the radiator instead of pulling it through, and thats enough will cause you all sorts of overeating problems.

2- In case you have a reverse flow water pump that would circulate the coolant to the cyl. heads first then the block, then I dont think the MkIV blocks are compatible with that cooling mechanism.

3- If you are using a standard rotation water pump and use it in a serpentine belt system, and thinking that this may work as a "reverse flow" cooling mechanism, then you are incorrect, the vanes inside the water pump will rotate in the wrong direction causing all sorts of turbulences and will eventually cause the engine to over heat.

With such a large engine in a tiny compartment with A/C running and setting idle in 100F ambient temps, 195F is not bad at all, in matter of fact I would be surprised if your engine will stay at that temp! .. my '71 with a BB engine will idle at that temp in a similar ambient temps but I'm using a large aluminum radiator and dual 11 in. electric fans.

 

Yeah, my apologies, my original post was a little misleading. The pump is a reverse rotation (not flow) pump designed as a direct replacement while adding a Vintage air serpentine system. The mechanical fan is a counterclockwise fan, so I am pulling air through the radiator. Maybe 195 isn't that bad, but seeing as I have over 12K in this engine bay I didn't want to see it go past 200. The fan is a low profile with small kerf fins, so maybe it's not pulling as much air as it needs.


18" CCW Flex-A-Lite

 

I see no signs of a fan shroud.

 

Sorry, older picture before the fan and shroud were installed. They are both there now -trust me.

 

That would be my guess.

 

Get rid of the POS flex-a-lite fans and get some dual Spal electric fans. They only run when the car gets hot. Mine have an on/off at 195/185 switch in conjunction with a 180 stat. Runs 180 on the highway all day long and fans cycle in town. Only way to go.

 

You're 100% right on. That was my plan (one of my winter projects once I get some more money together). For now I'm out of cash. I'm going to try some of that radiator additive - supposedly lowers your water temp 10-20 degrees - put the high-flow 180 degree stat back in and see where she's at.

 

Until winter, changing to something like this might help.

http://www.summitracing.com/parts/DER-17618/

Its still a flex fan, but I bet it pulls a bit more air than the one you are using now.

 

that serp set-up puts all the acss. in the front of the engine which leaves very little room to install a fan and shroud. I've been fighting the same issue with my car. Would love to see pics of the fan and shroud installed if possible.

Neal

 

Save your money. It doesn't work. There's no magic liquid that will do such a thing.

 

Mike's right on this one.....