One of the most common questions we receive here at Steel Seal concerns the build-up of back pressure in the cooling system. Although we do have additional instructions for people experiencing back pressure on our FAQ’s page, back pressure can be quite a complex issue to understand and especially confusing if you are not too mechanically minded, and many people are still unsure or struggle with the steps regarding Steel Seal treatment when back pressure is present. It’s for this reason we have put together this simple to follow article to help to explain a little about back pressure, how you can identify if you have it, and how you can treat it when using Steel Seal to fix your head gasket damage.

What is Back Pressure?

back pressure diagram

We can define engine exhaust back pressure as the exhaust gas pressure required to overcome the hydraulic resistance of the exhaust system, allowing the release of gases through this exhaust system, or as the resistance to the positive flow of the exhaust stream.
Problems occur when the back pressure becomes too great. When this occurs it can result in a number of symptoms, including a lack of high speed power, poor fuel economy, altered transmission shift points, backfiring and overheating (this happens as with the build-up of pressure there is also a natural build-up of heat. The heat that would normally escape through the tailpipe instead builds-up in the cooling system, eventually causing it to reach temperatures that overheat the engine). You will often be able to identify if you have back pressure by a bubbling in the header tank, or by air forcing past the coolant cap.

Back Pressure For Steel Seal

When it comes to using Steel Seal, back pressure is a problem as it can stop the product from circulating through the system properly and from reaching the problem area. Hence we have to carry out an additional step in the process before beginning the Steel Seal treatment itself.

When using Steel Seal there are two alternative methods that can be employed when back pressure is present, depending on both your level of knowledge and confidence around an engine, and the set-up of the engine itself.

1) The first (recommended) option is as follows:

Locate the cylinder causing the bubbling in the overflow tank or backpressure (Remove plugs one at a time till bubbling stops) .
Before starting the engine, remove the spark plug or injector from the cylinder that was causing the bubbling in the overflow tank or back pressure. If accessible, remove injector wire from that cylinder. This will limit the amount of unburned fuel going into the combustion chamber.

Make sure to run the engine up to temperature with the spark plug/Injector out and for the one final time with the spark plug/injector back in place.

In some engines you will not be able to remove the injector wires / spark plugs separately and will not be able to isolate the problem cylinder, and will need to employ the second option:

2) Alternate Method:

The alternative would be to either drain your coolant entirely, or at least enough to add the required amount of Steel Seal (to drain the system you will need to remove the hose at the bottom of the radiator), then add the Steel Seal and finally top back up with coolant until it just becomes visible at the bottom of your expansion tank.

We recommend draining the system entirely if you have either used another product before attempting Steel Seal, or if your coolant is dirty.

What you can then do is go through your treatment with the expansion cap off. What this will do is release the pressure when your coolant is pushed into the chamber and allows it to drop back into the system because the level is low and the cap off.

Finally, it is worth noting that although Steel Seal is designed to be a simple DIY Head Gasket Repair, if you are really unsure it may be best to get a mechanic to do the treatment.