Running HOT

OK, so here's a problem I've been working on. When I drive my car around town, or leave it idling the temperature is just fine. When I get on the freeway and drive at normal cruising speeds (55-65) over a distance of approximately 15 miles, the temp climbs steadily. With a mechanical gauge with the probe in the intake manifold, it has gotten as high as 220f.

I flushed the radiator (it WAS full of gunk at the bottom to the point that I had to remove the drain plug valve and poke a stick in until it started draining. Eventually got clear flow going from the cap on top on the driver's side and out the drain on the bottom on the passenger's side. Kind of ruling out the radiator at this point.

My guess at this point is that the impeller on the water pump has corroded to the point it supplies enough flow to cool at low speeds but not enough for the increased heat load at highway speeds. Any thoughts?

 

Clear flow means the hose is on full blast and the water is coming out as fast as it goes in. If so, that proves that your radiator is less than 70% blocked.
With the engine hot and the cap off, if you see water moving horizontally when you look down the fill hole your radiator is more than 25% blocked.
If you are running a fan clutch you should check that also. You can heat it with a hair dryer (when your wife is not home) and make sure it locks up.

 

Sounds like it's time for a new thermostat, water pump, and a radiator flush (you can get some stuff to run through both the engine and the radiator which will clean all the gunk out). Just be prepared for other possible problems to surface when this is done as there may be gunk plugging holes elsewhere in the system.

 

Climbing temp at higher RPMs indicates a compression leak into the water jacket. Your cooling system may be working as designed, but can't handle the extra heat from a compression leak.

 

If there is a compression leak there will be a fuel smell in the radiator. Also the cylinder with the leak will fill with radiator fluid when the engine is shutoff, so water in the oil.

 

As Don suggests, there are other indications...Look for foam in the radiator upper tank.

 

Improper igniton timing (insufficient advance) will cause an engine to run hot at elevated rpms.

 

Thank you for the suggestions.

@ 5.0 Chero, yes it is possible I still have blockage but I did verify good flow through the radiator.

@ ribald1, not sure the radiator outflow kept up with a hose on full blast but will probably just flush the right way - with a can of Prestone radiator flush.

@ steerhead and DonC, the coolant has no foam, not even a film of oil and the motor oil is not at all milky.

 

+1, the flush in a can is fine for routine maintenance but if you have a cooling system issue or suspect a blockage, the shop is the best way to go.
His way with words is sometimes... cryptic, but his wisdom is sage. Listen to this man.

 

So true. Carl has pretty much done it all, and I would listen to his advice.

In yet another werid Ranchero, 'Circle of life' moment; I used to live near a place called the Sagebrush Cantina, and their claim to fame was a huge 1 lb Grande Burrito, for $5.

 

I have pretty much the same issue with my 65 -- in the summer when temps get to be over 100.

I guess my lil microtruck was not really designed to maintain speeds of 75-80 in the heat.

Takes about 30 miles---but still gets hot, and if I slow down to 65 or less, it is just fine. Radiator was rodded out early this summer.

When it starts cooling off----like now with outside temps at hovering around 70, the gauge just barely makes the cold side of normal. But even this takes about 20 miles.

Yep---t-stat is there.

Now that I have a functional heater----those summer temps may come down a bit.

 

I'm with 5.0. I took the rad out of my 76 F150 and had it checked before making a 5,000 mile round trip to PA. They said the rad was good. I fought an overheating problem like described the whole trip. Ran cool at idle, or around town. Extended driving made it run hot. After trying everything described in these posts, flush, change thermostat, etc. (Heck, I even put a spring in the lower hose in case it was sucking flat at speed!) I decided to start over. Took the rad to a different shop and asked them to rod it out. Went back the next day to pick it up, and they said it was so plugged that they could not clean it out. Bought a new rad, truck runs cool at all times now. If you had to use a stick to get coolant coming out of your rad, it is toast!

 

I agree that in this case it's probably the radiator. However, I found out recently (by experience) that it is possible to have an overheating problem caused by a head gasket leak without getting any water in the oil or oil in your coolant. It's probably not common, but it can happen.

 

The last test needs two people. You need to simulate what happens when driving, but with the cap off. So...One person behind the wheel, brakes FULLY applied, revving the engine with tranny in Drive to approximate highway conditions. One BRAVE, BRAVE soul looking into the upper tank during the simulation. If you don't like this, then maybe run her into a solid wall, post, etc. with an old tire in between to protect the car.

 

I think this is the norm, and not the exception. A head gasket leak is above the rings, and any coolant "inhaled" on the intake stroke is converted to steam "white smoke" out the exhaust. If the rings are good, there will be no water in the oil, or vice versa. Have someone follow you while you are driving to see if you have "white smoke" out the exhaust.

Remember the exhaust rules: Clear is good, White is water, Blue is oil, and Black is too rich.

On the power stroke, however, much heat/compression is expelled through the leaky head gasket into the water jacket. Therefore the foam in the radiator.

Holy...Simple test for coolant in the exhaust: Hold your hand below the exhaust for a few seconds...until it gets uncomfortable. Then smell and taste it. If it smells and tastes sweet, then you've got coolant in your exhaust, which will only occur due to head gasket leak.

 

Yeah, in my case there was no mistaking the steam from the exhaust, and water (more than normal) dripping from the exhaust. I was also getting abnormal pressure in the radiator.

 

Are you using a fan shroud?
Without a shroud the fan can impede air flow at high rpm's.

 

Hmmmm.
No shroud-----wonder where it went-----did it have one new???

Something I shall remedy before the summer gets here again (should be late Feb). Also plan on getting a new radiator by then as well.

I don't have a lot of faith in a 47 year old 2 row radiator in this South Texas 105* 50%+ humidity.