Waterlock on Renault R8

[Jim Rice]

Twice this last summer we got a waterlock on our R8 diesel. Why? We didn't close the water intake after shutting the hot engine off. As the water cooled and contracted, it drew water into the muffler and from there back into the engine and into the cylinder!!!!!1) If this happens to you, DO NOT TRY AND TURN THE ENGINE OVER! Try turning it over by hand--you can tell if there is water in the cylinder, the darn thing will S-T-O-P. We were lucky, no damage (we hope).2) We had the yard out to the boat twice (ouch!)--learn from our mistakes:a) Shut the water intake seacock off after shutting down a hot engine (and DO NOT forget to reopen it before starting, obviously);b) install a vacuum break valve in the water injection line to the muffler;c) a good yard is beyond price, and sometimes calling them out is worth the cost.While I can't take responsibility for this advice keeping you out of the sort of hot water (!) we got in, this should help you avoid engine troubles.Comments anyone?

 

[Dan Bryant]

Question on R8

I also have a H27 with an R8, so you got my attention!I'm confused, though, regarding how closing the intake valve on the hot engine can affect water into the injection bend. Certainly no water (or air)is making it by the impellar when the engine is not turning, so how can the pressure inside the injection bend be affected by closing the intake valve? I can see the air contracting as it cools, and maybe drawing some water up from the container, but that contraction can't be much.So far (knock on wood) I have not had this problem. The only way I've heard of getting water into the cylinder is when folks continuously crack the engine with the intake valve open. That one I can understand: the starter keeps spinning the impellar and fills up the exhaust hose, but without exhaust pressure the cooling water can't make it out above the rise in the hose.Now you have me wondering!

 

[Jim Rice]

An Answer (of sorts)

I dunno how it happened, but it did it twice to me. The water couldn't have come up thru the exhaust (a route that has been described in the literature), we were on our mooring and the exhaust outlet was above the water. The siphon break seems to have done the trick, thus the original posting.