Reader Follow-Up

January 1, 2011 | By Staff

Cooling System Maintenance

enjoyed reading John Armstrong’s articles on Cooling System Maintenance in the August and September issues. However, I can think of a few problems that haven’t been discussed by John. Perhaps they will appear in a later issue.

Al Birks Waldorf, Maryland

Editor’s note: Here is Al’s list of cooling system problems along with John’s thoughts on the topics.

Coolant Distribution Channels (Or Tubes)

Al: One area that should be discussed is a check of the distribution channel present in the blocks of most of the straight 6- and 8-cylinder engines. These frequently rust out and leave part of the engine improperly cooled.

John: These channels or tubes can be found in Flathead engines, inserted behind the water pump with the purpose of directing coolant flow toward the valve seats, primarily the exhaust. With age these tubes can corrode or become restricted. This will reduce or even eliminate the intended accelerated stream of coolant aimed at the exhaust valve seats, which will lead to overheating. Furthermore, if a distribution tube has been installed without the proper orientation or left out entirely, overheating will occur. So if your vehicle is powered by a Flathead engine, check your shop manual to see if it utilizes this tube. Inspection will require removal of the water pump and possibly/probably the radiator. Should you need to replace your water pump, make certain to inspect this tube while doing so.

Coolant Level Indicators

Al: These devices are found in either the coolant overflow container or they are incorporated into the radiator. I have had trouble with my Coolant Level indicator—the dash warning light appeared and went out even though the radiator was full of coolant. I had to replace the sensor to quiet that warning light.

John: Newer vehicles have sensors for everything. They know when there is moisture present on the windshield and will activate your wipers, and they can even tell you when the tires require inflation. All sensors are subject to failure, and if your vehicle is equipped with a coolant level sensor, it is by no means exempt. If you experience false alerts from a warning light, first locate the sensor, then inspect the connection and wiring for any obvious problems. Due to the under-hood environment, you are more likely to find wiring/connection problems there, as opposed to under the dash. Your vehicle’s shop manual should outline a specific test procedure for this sensor.

If it is not too expensive, you can take the “educated guess approach” and replace the sensor.

Inspection of Used Engines for Cracks

Al: To ensure that your newly purchased used engine block and heads are crack-free, John should urge readers not to trust their vision alone to detect the presence of cracks that will later be the cause of major coolant leaks. The correct solution after a preliminary visual scan is to have your engine shop use a magnetic particle tester on the heads and block to detect the tight, invisible cracks.

John: If you are purchasing a used engine that you are unable to see in operation, exercise extreme caution. Unless someone is virtually giving it to you, make sure you know the reputation of the dealer or individual you are dealing with. What is their guarantee? Ask the seller up front any “what if” questions you can think of. And as Mr. Birks has suggested, having an automotive machine shop use a procedure such as “Magnaflux” to check the engine castings for cracks is a smart choice for an unknown engine before you invest additional money in machine work and parts.

Oil In the Coolant

Al: Look for leaking gaskets between the intake manifold and block, or gaskets between the block and heads. A simple CO/CO2 detector used at the radiator filler will help to isolate and verify the presence of internal cracks and gasket failures.

John: This could represent internal leakage, but some water pump lubricants mixed with the coolant can resemble oil in the coolant.

To verify if there is indeed an internal leak, I would rely on a combustion chamber leak detector like the one originally shown in Photo 8 on page 12 of the August 2010 issue of Auto Restorer. (That photo has been reproduced at the bottom of this page. If exhaust gases are getting into the cooling system, the color of the test chemical in the detector will change.)

And one last observation: The cooling system maintenance articles were intended to cover in-depth maintenance, but weren’t intended to cover all the various overheating issues that we can face. While there is certainly some overlap in these two topics, covering the many possible causes of overheating goes off into a direction of its own. There are many common factors, but some overheating issues can vary depending on the engine and vehicle. Mr. Birks’ point with regard to the distribution tube is a good example of this.