greeta

I had just bought the car (Stock 289) and noticed that after driving and then idling the temp on the guage would approach hot (but not go over). Many times when I stopped I would notice that there was antifreeze on the ground from the rad cap releasing. Again, the guage has never indicated over HOT, but maybe about 1/4" under. As soon as I got on the highway the temp would drop down. I changed the rad cap to a 13lb unit and the boiling over on the ground issue somewhat disappeared although the temp never dropped.

So I decided to do some upgrades to the cooling system. I bought the most heavy duty rad I could from NPD and a new 5 blade fan. The rad is much thicker than the existing one and should have far better cooling capacity. After making the changes, it is even WORSE than before. It does not cool any better and I cannot keep water in the rad........Here is what is going on.

I have only driven the car on short trips to the local town since. I noticed that after driving for 15 minutes on the highway the temp was around 1/3 up the guage. Idling in the city would bring the temp up to about 1/4 below the Hot line. On the 15 minute drive home the temp would drop to about 2/3 up the guage; which was somewhat higher than before. I am not sure if this is as high as it was going to go or that this was only as high as it got in 15 minutes of driving.

What I did notice is that there was a lot of antifreeze on the inner fender wells and under the hood. I checked the level in the rad and it was way down. I have checked this after each trip (30 minutes or less total driving time) and it is always the same; there is almost no water left in the rad. This was confusing since the temperature never registered hot on the guage, there was never any steam coming out of the motor compartment, and there was never any coolant on the ground when stopped or idling.

I was not sure where the coolant was going to so I put the tube from the rad cap fitting into a small plastic bottle I located at the bottom of the rad to see if it is boiling out the rad cap. I went on a 10 minute drive and the guage went to about 1/3 max. When I opened the hood the container was right full and had also been overflowing. The engine itself and engine compartment did not seem to be overly hot. I was there for at least 10 minutes and in that time there was no coolant of any kind came out of the cap and not even a single drop went on the ground. When I got home I put at least 2 gallons of water in the rad. Every trip is the same.

The problem is not there when it idling. When first started the car can idle forever and will only go a 1/4 way up the guage. It does not boil over at all. I tested this and let the car idle for at least 30 minutes at an outside temp of around 80degrees. Even after driving the car, it does not boil over when idling, only when on the highway. At no time does the guage register that it is hot.

Here are the particulars of what I have done or checked.

1. The thermostat has been removed and there is no change of any kind
2. When idling I remove the rad cap and I can see the water is moving and the water pump appears to be working.
3. The new fan is installed so it pulls air through the radiator.
4. The car has AC. The condensor is not plugged and has been cleaned with a hose.
5. I have not checked or confirmed operation of the guage. Although, when it indicates that the motor is at hot, you can tell there is a lot of heat coming off the motor.
6. I put the rad cap I got with the car back on with no change.
7. Since the first few trips, I have been filling the rad with water and no antifreeze.

If the temp guage and rad cap are both working, than there is high pressure at acceptable temperature. Is this possible? I read somewhere that the lower rad hose can collapse if not of the internal spring type. This might make sense to me because if the lower rad hose collapses it would cause a restriction in the outlet of the rad. Because this is a closed system, the pump would build pressure and the rad cap would release after 13 PSI. At idle (lower rpm) this is not a problem as the pump would not build the same pressure. I also am sure the last trip I witnessed the guage surging somewhat under acceleration. It almost was like someone was opening and closing the water flow in the system.

Any help with this would be greatly appreciated. Right now I can only go on 15 minute trips(one way) unless I carry my own water supply.

gjz30075

It's quite possible a head gasket has blown and the break is between cylinders. That's where the high pressure would come from. When I first started reading your post, I thought maybe you were overfilling but losing 2 gallons is something else.

You might want to pressure test the cooling system. If there's a break in the system somewhere, you'll hear hissing coming from the crankcase.

2+2GT

Always use a 190° thermostat. Always use a 50/50 antifreeze mix. Never fill the radiator higher than 1" below the seal ring under the radiator cap.

greeta

How would I do that? What kind of pressures should I be looking at?

dklistul

You can probably rent a cooling system tester from an auto parts house.

You remove the radiator cap and connect the tester in place of the cap. If you're using a 13 pound cap, pump the system up to 12 or 13 pounds. Once pumped up, reading the gauge on the tester over the span of 10 or 15 minutes will tell you if there's a leak.

Simple test to do. If you want to buy the tester, Summit Racing sells a good one from OTC for about a hundred bucks. Whatever tool you use, follow the instructions on the tester and DO NOT exceed the design pressure of your cooling system.

boogerschnot

Sounds like a head gasket to me too..

Tilley

I had the exact same problem as you have...turned out it was a head gasket.

gjz30075

An example of what a pressure tester looks like:
http://www.ebay.com/itm/Cooling-Syst..._Tools&vxp=mtr

67 evil eleanor

If it was me I'd start with the simple things first. Fan shroud, fan designed for an A/C car. Using antifreeze 50/50 insted of water. Do you have a shroud. Is there a clutch on the fan? Picture of your setup would help also.

merc64

I always start cheap and go from there. Before pulling off the heads I'd change out the hose with one that has a spring inside to stop it from collapsing. I'd also drain the block and then power flush the whole system. Maybe you just have a blockage and it will clear out. You didn't say but is it possible the previous owner did a rebuild or refresh and replaced the head gaskets? I only ask because some people can put them in wrong and unknowingly block a water jacket. Also, you said you put a new thermostat in, did you test it to make sure it was opening? You can get a bad one from time to time. They can be tested by boiling water on stove and making sure they open.

I'd buy a cheap infra-red thermometer to check your actual temp. They are cheap and can be found at most auto stores. Those old gauges aren't too accurate.