If there are combustion gasses entering the cooling system they will show up with a good quality gas tester.
Failing that a thorough cooling system pressure test as I mentioned previously, plus, as Stocktake mentions a compression test.
One other not often mentioned or used is a cylinder leak tester, or leak down tester.
Basically it has two pressure gauges on a tube, one end has a connection to a compressor, the other end has an adaptor to screw into plug holes, between the gauges in the tube is a calibrated restricted orifice.
The first gauge measures input pressure which you usually set at 100 Psi. the second measures the leakage as a percentage.
It can be a bit of a rigmarole the more cylinders there are but can provide so much information.
Briefly, take a 4cyl engine, remove all the plugs, get No 1 to TDC both valves closed, put the car in gear to prevent the engine turning fit the adaptor into No 1 plug hole, then turn on the air and set the input gauge at 100 Psi, observe and note the reading on the leakage gauge, there will be some leakage, also fill the radiator or expansion bottle to overflowing, remove the dipstick and oil filler cap and remove the air filter to carb, throttle body pipe, then whilst all is still connected and under pressure, listen at the following for the sound of air leaking, sometimes easier with a stethoscope or piece of tube.
A) Exhaust pipe, signs of a burnt valve or no valve clearance, or other valve / seat problems.
B) Carb, throttle body inlet, as above, valve / seating problem etc as with the exhaust.
C) Oil filler cap and, or dipstick tube, possible ring damage or ring bore wear/ damage.
D) Radiator filler neck or expansion bottle neck, visible bubbles, or if not filled to overflowing sound of escaping air in the expansion bottle or radiator, signs of head gasket failure or cracked liner or cracked head in some instances.
E) The plug hole of the adjacent cylinder, or cylinders to that being tested, shows head gasket, cracked head problems between cylinders.
Obviously as each cylinder is tested, it must be brought to TDC with both/all valves closed and the above repeated, a healthy engine will show all cylinders leak a small amount and about equal and this will be past the piston rings, any with a greater leak points to that cylinder only.
It can show single areas needing attention as above or multiple areas.
If you get time Google a video of it, a video will explain far more than my brief description here.
Stocktake also mentioned Steel Seal, though not the cheapest sealer, it is about the best according to my son, though not intended be to a permanent repair, as long as the instructions are followed to the letter, he has been surprised in many instances how well it has worked and how long it has lasted on customers cars who have been skint, just wanted the car to last another couple of months, or to save up for the proper job to be done and having stripped them down for the proper job at a later date has been able to see how effective it has been, but it won't always work on substantial problems.
The testers are quite reasonable and you can make one, as I did aeons ago for two reasons, one I'm tight, two I'm always of the mindset of " I bet I could make one " the photo is of my Blue Peter, Heath Robinson one, after a bit of rooting in my ' that may come in handy, cabinets, drawers and cupboards' and it's as accurate but not as posh as my sons.
https://www.flickr.com/photos/225857...posted-public/
2nd April 2021, 07:13
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