Winterizing--No Flow with Bypass Closed!

[ghaegele]

Help! Cold weather quickly approaching and I can't winterize. There is no flow through the block when the bypass hose is clamped closed.

The history is a rebuild late model A4 6 years ago. Raw water cooled.

This season I had some overheating and kicked myself for not doing an acid flush since rebuild, but it had been running great since rebuild. Overheating was controlled by throttling back. Flow out exhaust seemed light, but when I pulled the wet side exhaust hose there was decent flow. So I postponed flush to next Spring.

Began winterization. I ran engine with good coolant flow, drained oil, added MMO, ran to distribute, revving as water from bucket cavitated. Drained water jacket. The drain plug on manifold has been frozen in place so I skip that. (No access to drill out and retap).

When I removed the thermostat the cavity for therm was packed with scale and rust! I spooned out the scale and poked head passages to clear more scale. Then replaced therm housing (no therm), clamped off bypass, and started engine to draw antifreeze in. Nothing moved.

I then shut down, pulled the therm housing off and bumped the engine, confirming flow into therm from water pump. I then tried to blow back from outlet at rear of manifold and, with bypass closed, no flow whatsoever. With bypass open flow is fine. Opened water jacket drain and tried to blow--nothing.

Any suggestions? I figure I have to pull the manifold and clean the passage from block into manifold. I don't think acid will work as can't draw into block. Is there a diagram of flow through A4 block and head?

[ndutton]

There is no passage from block to manifold, coolant passes through a hose from one to the other.

I'm not a winterizing guy but if I were, the freeze damage risk is so great I'd get aggressive and pull the side plate, manifold and head to really get after the scale and rusticles, get all the passages rooted out, take the head, manifold and raw water pump home for the winter.

I'll defer to the snow belt guys but I think that should get all the water out of the block and keep you safe until Spring.

[hanleyclifford]

There is no passage from block to manifold, coolant passes through a hose from one to the other.

I'm not a winterizing guy but if I were, the freeze damage risk is so great I'd get aggressive and pull the side plate, manifold and head to really get after the scale and rusticles, get all the passages rooted out, take the head, manifold and raw water pump home for the winter.

I'll defer to the snow belt guys but I think that should get all the water out of the block and keep you safe until Spring.

+1 - and I would add, fill the block with automotive antifreeze and get rid of the thermostat permanently since they are especially pernicious in a RWC engine.

[ghaegele]

Ndutton: No winterizing? You are missing all the fun!

Okay, so I just got to a diagram of the flow and you are right and I feel like an idiot! All of the flow into manifold enters from the "crossover" line. The the bypass is the line from the "T" fitting to the therm housing. By clamping off the cross over I shut down all flow. Then, when I released, flowed fine. Grrrrrrrr!!!!!

With the overheating I immediately jumped to major blockage rather than user error.

[ndutton]

Yeah, big difference between the bypass (between sideplate Tee and T-Stat) and crossover (between T-Stat and manifold). Easy fix and now you can get that acid flush done.

With all the scale and rust you described don't discount blockage. Plenty of excellent threads on it.

[ghaegele]

Very easy fix. Just remove the damn clamp I put on the wrong hose!

The really stupid thing is this is not the first time I have winterized the engine (though it has only been the last few times that I have followed Don's advice to clamp off the bypass to ensure filling the block. The bypass.

[JOHN COOKSON]

I removed the temp sending unit, put a nipple in its place, then put a piece of tubing on the nipple the other end in the bilge, started the engine revved it up a bit and blew a bunch of KRAP out. If you did this it should reduce the amount of KRAP in your engine.
Have you considered FWC?

TRUE GRIT

[ghaegele]

I have considered FWC but the engine compartment in my C&C 35 is prohibitively tight.

Now that I am certain the only blockage was in my brain, I still need to clear out the crud in the engine--probably in the Spring so long as the winterization proceeds without issue.

I read the acid flush / pressure flush procedure. Question: when to employ which procedure. If in my situation it is both, in which order? Pressure flush first, then acid flush to get anything left behind?

[JOHN COOKSON]

I'd do any fresh water flushing first. Reason: The fresh water will dissolve some of the salt build up and leave less "work" for the acid to do.
I have a feeling that in the end you are going to end up with a squeaky clean cooling system.

TRUE GRIT