Overheating at idle ...

[Jamie Miles]

I live in the Atlanta area and commute on Peachtree Industrial blvd., Jimmy Carter Blvd. and Interstate 85 North on a daily basis with my '72 Maverick. I'm usually comeing home at about 4 P.M.

Driving through that area at 4 P.M. in mid July, 2 things are for sure. There is LOTS of stop and go traffic, and it is very, very HOT and humid (the smog dosen't help much either).

My car was running 210-230 degrees continously, no matter my driving speed. I finally tracked it down to being that my timeing had slipped. I reset the timeing to 6 degrees BTDC, and my temperature has dropped to about 190 when driving above 30 mph. The problem now lies when sitting in stop and go traffic, which about 75% of my commute is stop and go in the afternoon (it takes me over an hour to go 22 miles). My car is getting up to 230+ degrees in stop and go traffic. I am beginning to fear that it will spin a bearing or blow the head gasket getting that hot.

The only way to cool it down is to put it in neutral and hold it at a steady 2,000 rpm. It will usually drop down to about 215 when sitting still and revving it. I do not have a fan shroud, do you guys think that would help with my idle temp? Also, do you think retarding the base timeing a little more may help? When I reset the timeing this last time, my 30+ mph driving temp dropped drastically and my gas mileage went up alot also.

My engine is totally stock 250 from a 1974 Maverick Grabber, 210,000 miles (I know, alot of miles, but it still runs alright), with a Duraspark II upgrade and TFI coil. I do have a large transmission cooler which is mounted to the front of the radiator and covers about 85% of the radiator. I currently have a 180 degree thermostat in it. I replaced the 4 blade fan with a 6 blade fan from a 6 cylinder factory A/C Maverick that was in the junkyard. It seemed to help some.

Any tips to get my temp down in stop and go traffic would be great. Sorry for the long post.

 

[80Stang]

-Try some more initial advance, say 10-12*.

-Consider again your tranny cooler; does it really need that big thingy there? There are new affordable coolers available that are not that big.

-Consider an electric thermostat controlled puller fan. You can add a switch in cabin to switch it ON continuously when ever you have to crawl in the traffic or sit in the traffic lights.

-Check that you are not running lean at idle.

Just some thoughts...

 

[MustangSix]

rule of thumb:

overheat at idle = inadequate airflow
overheat at speed = inadequate radiator capacity

A fan shroud might help, but I think you may have a partially blocked or clogged radiator. The additional airflow at speed and when revving it is helping the cooling, but the radiator is not operating at full capacity.

If it were me, i would pull the radiator and backflush it as a first effort. You may find a bunch of stuff clogging some of the tubes. It may even take a radiator shop to clean it really well.

Check the fan belt to make sure it's not slipping and that the fan and water pump are working to capacity.

 

[mjpchief]

Something that people don't think about are the cooling fins in an older radiator. Check them and make sure that they are still attached to the radiator tubes. If they have become loose the radiator will loose its cooling ability. Make sure you can't move them up and down on the tubes.

 

[Jamie Miles]

After burning up 2 C4's in 4,500 miles, I was told by several transmission gurus to get the biggest trans cooler I could find. So far, so good. I have 9,000 miles on this transmission with no problems.

The radiator being clogged is a VERY good possibility. The engine and radiator have been together since the factory (210,000 miles on both). The car they came from had been sitting for over 12 years, and there was a good bit of rust and debris in the coolant when I swapped the engine and radiator over to my '72. I flushed the block and radiator at that time, but I'm sure I didn't get it all, as my coolant once again has a slightly brownish color to it. I just bought an almost new 3 core radiator (one currently in there is a 2 core), just haven't had time to put it in yet.

It dosen't seem to be idleing lean, but I will check it out.

Thanks for the suggestions.

 

[LaGrasta]

I'm a huge fan of electric fans. Dump the mechanical. They work the direct opposite time of each other with the electric fan working when it really matters most.

 

[CobraSix]

No need to run anything but a stock set up. A stock cooling system is more then adequate when in good working condition. I can let my system idle for an hour at 100* outside temp and the temp still never goes about 180*.

I could be either your radiator or water pump. I'd change the water pump first as it is probably needed anyways and is cheaper then the radiator. Some of the symptons you describe sound water pump related like running it up to 2000RPM while parked to cool it down. The difference in flow caused by the fan between 1000RPM and 2000RPM really isn't enough to make it cool down significantly like you describe (at least not from what I've seen) which points me to your water pump as a possible culprit though the radiator is a very strong possibility.

While you are at it...replace all your cooling hoses just to be sure.

 

[Jamie Miles]

All the hoses are less then a year old. The water pump is at least 30 years old, possibly original to the motor (1974). The guy I bought the car from that the motor came out of had owned the car since '76, and said he had never replaced the water pump. I have been going to replace it, but it's just been one of those "when I get around to it" things.

I will replace the radiator since I already have one and see what that does. I will let you guys know.

 

[Jamie Miles]

It was rediculously hot today on the way home. I was sitting in stop and go traffic on Peachtree Industrial Blvd. and before I knew what was happening, the thing pegged the temp gauge at 250 degrees. It boiled over in a BIG way and totally engulfed 3 cars behind me in a big cloud of smoke. This guy pulled up next to me and gave me a thumbs up and said "Nice one!" (I think he thought I did a burnout or something LOL). It was embarrasing as hell, but at the same time it was hilarious.

I pulled off and raised the hood, felt like I got hit by a Mack truck with all the heat that rushed out. I let it sit for about 15 minutes and started it back up. Soon as I did, the temp quickly dropped back down to 220. I drove on home without it getting above 230 the rest of the way home.

I am heading out right now to replace the radiator (even though it's still about 93 degrees out at 8:15 P.M. ). I don't think that old motor can handle that happening again. Thank god I have a few low mileage spares engines...

 

[CobraSix]

While you ahve the system drained for the radiator replacement, re place the water pump! 30 years old...it's impeller is probably full of holes as it is more then likely cast iron.

Slade

 

[LaGrasta]

yes, replace the water pump. it needs it, you're already are in there and they don't cost a lot anyway.

 

[johnnyzoom]

Thermostat's probably less than $8 too...

 

[Jamie Miles]

Thermostat's probably less than $8 too...

The thermostat is only about 3 months old. I will get a water pump tonight.

Thanks.

 

[Jamie Miles]

Well, I didn't replace the water pump because my dad insisted that it's not the problem and that you don't need to replace them unless they are leaking.

I put the new radiator in and drilled a couple of holes in the thermostat at my dad's advice. I also flushed the block, looked about like chocolate milk comeing out of there! So far, so good! The car never goes above 180 on the interstate and never goes above 195 in traffic. If you rev it in traffic, it will drop down to almost 160. My dad says to put a fan shroud on it and that will help with the temp in traffic. So I'll do that.

Thanks for the help guys.