Sludge in water jacket

[andrewk]

I've had a seeping frost plug (welch plug for some of you) for a while, the rear one of the two on the exhaust side. With the approach of a southern hemisphere winter I decided to get into it yesterday. I really wasn't prepared for the sheer volume of gritty sludge in behind there. The coolant is clear green, the operating temperature is fine, the radiator is clean, there's a two year-old Burton cassette pump working well, but the amount of crap in this water jacket is amazing. I've removed an egg-cup full with a small spoon but there's no way of getting much more of it out that way.



Now some of this has been disturbed, if I just reassemble it I fear that it may clog up the radiator and/or damage the water pump. I wouldn't mind some sage words from others. I guess I could flush from the thermostat housing with the lower hose blocked off. Or perhaps there's some additive that people have tried and found effective that is used once reassembled.

Or perhaps I'm worrying too much?

[alan.barker]

Imho you need to remove all core plugs.
Then use a karcher or pressure wash inside all core plug holes.
to assemble new core plugs i have used a Loctite for core plugs to be sure they don't leak.
Alan

[ericbushby]

Yes I agree, get it clean while you have the opportunity.
Be careful with the coreplug on the rear face. If you are knocking one side of the plug in, think that number four cylinder barrel is only a few millimetres directly behind the plug.
Best of luck,
Eric in Burnley
S3 DHC

[rgh0]

Sludge build up in the bottom of the block and the resultant corrosion is the main reason why blocks come to the end of their life. I have collected a lot of spare blocks and thrown away just as many as the cylinder wall thickness at the bottom of the water jacket was just too little. I have also seen quite a few race engines fail from building engines on blocks with too little metal left above the centre main bearing.

Flush as much as you can back through the block drain and the removed plug. You should be able to get most of it out. Use a flexible small hose to reach in from the plug to get to flush water in the area around other cylinders. Then reassemble and flush the block more with fresh water out the drain and refill and use with a coolant flush product and drain a refill and use the flush product flush a second time. Drain the block fully when drain out the flush product and fresh water flush out the block through the drain each time also. After a couple of goes you should have the block reasonably clean so that coolant and its rust inhibiters will be able to protect the bottom of the block and not be stopped by the sludge. Ideally you would strip the engine and chemically clean the block in a hot bath but that's not really doable unless you are doing a full rebuild

cheers
Rohan

[mbell]

I found the same, while changing mine with the engine out. I also used a shop vac to suck out as much as I could, as well as water and picking at lose stuff..

On refit the engine I back flushed it, by filling it from the top hose with the block coolant plug removed, as that washed most of the lose stuff straigth out the engine. Then a number of fill/drain flushes as suggested.

Based of a sample size of 1, I would be concerned about the rear plug (behind the flywheel) on your engine. My had corroded and had leaked but wasn't leaking due to all the crud blocking it back up. If yours is in similair condition it may start leaking after removing the crud, so keep an eye on collant level and any signs of coolant from rear of the engine after doing this.

[andrewk]

Thanks everyone for the good advice. I have to hope that the rear frost plug is OK because I have no plans to remove the engine at this stage. Time will tell.

[alan.barker]

You'll have a job to replace correctly without removing engine.
Best to remove engine and all Core Plugs. It's the only way to flush/clean correctly.
Your choice of course but the back Core Plug is the one people don't bother about and regret it later.
Alan

[mbell]

You'll have a job to replace correctly without removing engine.

I managed to replace one in situation fine after a replacement I obviously fitted badly when I had the engine out leaked. The key was to invest some money in a tool designed for the job (e.g. OTC Tools 4603) and a decent size hammer.

Wasn't the easiet job but not the worset on the car by far.

[RichardHawkins]

Andrew,

You did not mention where and how the plug was leaking, was it through the plug or around the plug? If the leak was through the plug, as in my case, then probably the other plugs are in a similar condition, and in my case they were. If it was around the plug then you may only have this one plug leaking.

Hope this helps,

Richard Hawkins

[alan.barker]

I use Loctite for Core Plugs to be sure of a good seal.
As said if one is rusted through the others will be the same.
Alan