After installing the FI system I finally got some time to get some run time. Went out and ran around the block. OK Not enough heat. Go for a longer ride and the temp gauge climbs all the way up to about 240. Pull over shut it off. Little bubbling in the system but not boiling over. Wait 5 minutes and figure I'll just get it home with a few cool downs. Drive home it stays cool. The fans cycle normal when it sits for a little while everything looks normal. I let everything cool down. Go out and the same thing happens. It seems like the motor gets hot but not sending enough heat right away to the thermostat to open it up. The fans are not kicking on and the sensor is right next to the T stat in the intake. Once I let it soak with heat everything operates normal.

Yes it is topped off with coolant. Running a high flow T stat at 195 degrees. That is needed for the FI. Dual Spal fans Dewitts aluminum radiator. Once it is running normal it stays at about 180 to the highest is about 200 degrees then the fans kick on and it cools it right down. I have pulled the thermostat and put it in boiling water and it start to open at 190ish in the boiling water.

BTW the FI works very well. Still need some run time for some more learning but it is getting better.

 

change thermostats. a 195 should start to open at about 175 and be fully open at 195 . if it starts to open at 190ish its not working correctly. i dont think its all of your problem but it will help. did u drill a 1/8 hole in the side plate of the t/stat to allow an airpocket pass cause it sound like an airloc problem. bottom rad hose still have the spring in it? on a good note glad your F.I is great !! wish i had it.

 

no help with the cooling but i am curious as to which FI you used

 

Simple (silly) suggestions. Did you drill a small hole in the thermostat? Condition of hoses? Correct/calibrated temp. sending sensor?

 

Sounds like air trapped in the system, drill the hole.

 

The thermostat is not the standard flat plate type. It is the high flow type. I know what you guys are talking about drilling the hole but this type does not lend itself to drilling it. Hoses are fairly new and the spring is in them. It was working perfectly last fall before the FI changeover. Only thing new is the thermostat and intake manifold. I'll drill the thermostat but where?

 

You can get a Mr Gasket or Robert Shaw, they have the hole and they are fail safe. PG.

 

You do have a bypass hose, right?

 

It is a Robert Shaw type of thermostat and it is a small block so no bypass hose.

 

Doh...

 

Ok, you've addressed the thermostat and hoses. What about the sending sensor in relation to the gauge?

Also, have you shot it with an IR gauge?

 

Yes the temp is slightly off I know that. What is happening though on the first heat up of the engine the temp goes to way hot, I only let it get to about 220 but it was still climbing. I shut it off. let it sit for 5 minutes to cool down but it also gets the whole motor warm now. I fire it back up and the temps never rise above 200 again. If I let it cool completlty down the cycle starts over again. Why is it not opening the first heat up of the motor?

Yes I have an IR gun and checked it. That is how I know the gauge is slightly off. It never did this in the years previous though. Just when I installed the new components.

 

If the only real change you made is the thermostat, that is most likely the problem. New stuff comes up 'bad' all the time. Change it to see what happens.

 

Ya' know i just a real odd ball cooling problem with my camaro. When i repowered it i had a new rad installed too but i got cheap and put in a Auto Zone cap. Well my new engine was using water too and giving a coolant low light frequently. Just a hunch or wild guess really and i replace that Auto Zonie cap with an stock AC Delco cap (both had correct press rating). Coolkabaam! Everything in the cooling sys is back to normal and working as good as new.
Someting with the way the AC Delco vents its self after shutdown is unigue and needed to get the job done on my camaro at least.

Oh BTW, keep your overflow hose (from the rad cap) covered in the overflow bottle.:o


Hope this helps Gordon,
cardo0

 

I put the Robert Shaw in mine and still drilled a few holes near the edge of the thermostat just to aid in bleeding the air. So far so good. The dang thing may stick next time I am out.

 

I guess I'll be pulling the T stat out and drilling some holes.

I do have an AC Delco cap on mine and it is fairly new. Probably 4 or so years old. The over flow on a 72 LT1 with no air just goes to the ground. No bottle or anything. I am using the windshield washer jug now as the overflow because drag strips require some type of over flow. It has been working fine for the last 5 years this way.

 

Here is where you drill the hole(s) in that style tstat.




Here is likely what is happening.
Cold, the radiator is full, but there is an air pocket under the tstat because you have no bleed hole, resulting in the fan switches and tstat not operating properly.
You run it and it overheats, possibly expells air and/or coolant thru the rad cap because both expand when heated. Now you might even has less coolant and more air. You let it sit hot and the tstat eventually thru convection opens. Now when restarting hot, you have coolant running thru the tsat and by the fan switch and everything is OK.

Then you let it get cold again. The coolant that is left in the system contracts again and you have the air pocket under the tstat again and the whole cycle repeats.

Remember the old systems without the coolant recovery tanks. If you looked under the rad cap the coolant level was 2 or 3 inches below full, cold, and fully at the top when hot. This gives you an example of how much the coolant will expand.

After you drill the holes in the tstat, refill SLOWLY cold, make sure you fill your recovery tank full and that the line from the rad to the tank is leak free. Check to make sure you have ther proper style cap. After a couple hot cold cycles, your system should be completely full and your problems gone.

BTW, a sbc does have a coolant bypass, built into the water pump pass side boss.
If you have at least 3 1/8" holes in the tstat and you want a little better coolant flow, you can block that passage off.

 

Thanks noonie. I was wondering where to drill the holes. How you explain it is exactly what I was thinking was happening. You just explained it very well. As I said above the LT1 recovery system is non existant. The rad if I fill it up to the top cold will expell about a pint of fluid at operating temps. It has always since I owned it after cool down the level is about 2 inches below full. I'll just drill the holes as you picture and fill it carefully. Thanks again.

 

A real recovery tank from a 77 or so is only about 25 bucks, so you might consiser that even if you don't go to the track.

 

I thought my windshield washer jug was a heck of an idea!