Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Cleaning water jacket....

Any good tips for thorough cleaning the waterways in the engine block while in situ?

Just had to replace a core plug, and she's got a fair bt of crud inside. Currently waiting for a new hose so scraped out a fait bit and put the new plug in, otherwise I could have got a hose in.

There's quite a few proprietry 'rad flush' treatments I could use. She's not blocked - maintains temperature really well.

I have over the years flushed out a couple of rads both main and heater matrix and have dull memories of flushing out an engine while I had the rad out for flushing.... The thermostat would need removal first. and after the initial surge of crud reversing the direction of flow seemed to dislodge a tad more crud, which encouraged me to carry out the reversing process a few times more till the outflow was clean.

It also seems a bit like oil choices, one may require to be selective when choosing antifreeze types given all that seems to be available now..?

Good luck.

I took the opportunity of a free day in the Man Cave the other week to flush out the engine, radiator & heater unit on Morgie. Same as you, at first, the stuff running out was more like cold strong coffe in colour, so I kept pushing clean water through until it ran clear - then I reconnected the bottom radiator hose; took off one of the hoses to the heater & stuck the garden hose in there and started again - relieved to see some grungy stuff run out, which gave me confidence that I had “reached parts that others don’t” 🤗.

Once everything had drained, it was a simple matter of refitting the hoses & checking all of the circlips for tightness before refilling the system with a 50:50 mix of Bluecol Antifreeze /Water.

I then ran the engine static for a while, stopped it, checked the expansion tank, topped up a bit, then ran the engine, again static, until the electric fan came on.

Finally, out on the road for a ‘steady’ 20 minute drive & home to check for leaks & levels: All good - now seeing about 10 degree lower temperature on a normal run.

The only time I did it in the 80s it was a garden hose job. As said above with reversing the flow. On our Renault 5 TS the heater box was full of crap I remember.

I did it too on a mk1 mx5 heater. It got it started again. I used a hose in the reverse direction but make sure you don’t use too higher pressure. There are some good videos on YouTube Such as this One. https://youtu.be/s--5ft5YiHg

You can get liquid flushing aids for central heating systems and they are safe with multiple metals, I wonder if that would help ?

Sounds like a good idea Cooperman! Someone recommended caustic soda years ago but I've never tried it although I've found that reverse flushing help.

One product that is made for cleaning the cooling system in place is called Evapo-Rust. They make a product that can be run in the cooling system for a time as coolant. Some leave it in for a month or more and it will leave the cooling system rust free. I am not sure if it is available outside the U.S. It is about $30 U.S. per gallon. https://evapo-rust.com/

The other thing you should consider is a filter in the top radiator hose. There are commercial ones made (Gano Filter), or many use a piece (toe section) of nylon stocking clamped between the hose and the radiator inlet pipe to filter the water coming from the engine. The filter will catch chunks of rust that break loose from inside the block before they get into the radiator and plug things up.

Thanks everyone for all the advice and help.

I've found some of the evaporust stuff (called Thermocure).on ebay. Will give it a go.

Will give the block a good flush back and forth, then will add the Thermocure, run for a few days and flush again.

Think I'll skip the filter - I fear it may block with time and reduce water flow?

Part of the annual maintenance on a Stag.

Simple but messy in a wet type of way. Run the water from a hose at medium flow, run for about 5 mines the reverse the flow. Repeat until it flows clear in both directions.