Overheating diagnosis

[calebsurfs]

Hi, this is my first post to this forum but I have found a lot of answers just searching here in the past. My 1969 Columbia 28's atomic 4 has been overheating the last couple times I have motored out of the slip. Very little cooling water is coming out the back.
I removed the water pump, which appears to be an Oberdorfer 202, and the rubber impeller is intact. I ran bucket water through a hose to the engine, and water was not circulating, though the hose has cracks and i doubt the pump had a good seal for suction. When I hooked the hose up to the faucet and gave it a little bit of pressure I got water circulating out the exhaust.
I was planning to suck the water lines with a shop vac and see if anything came out but they look pretty good. Should I just spring for a new water pump. Does the water pump simply need some fresh grease? Not sure where to go from here, I will look forward to your responses.

[Al Schober]

There are numerous places where the A4 cooling system can clog. You don't say whether you have a heat exchanger, what type of exhaust system, or whether you have a raw water strainer.
For starters, I recommend you remove the thermostat. Get the engine running cool first, then put the thermostat back.
Recommend you consider things piece by piece - for example, is the inlet blocked? Disconnect the inboard hose and open the valve - does water flow? Parts like the manifold can be checked by disconnecting the hoses and then blowing through. Should be much easier than blowing up a balloon.
Let us know how you make out.

[Marian Claire]

Welcome to the forum. I can only assume the engine was running when you tested with the pressurized water flow. How did the volume of water exiting the exhaust compare to what you had before? If the flow was much more than you had been getting I would think the pump or a blockage upstream from the pump is the issue. I would recommend a new pump after checking upstream. Then disassembling the old one and see if it is worth rebuilding as a spare.
Using a pressurized water system to provide water is not recommended.
Dan S/V Marian Claire

[BunnyPlanet169]

Caleb: Welcome to the Forum!

To echo what Al and Dan said, there are a lot of ways for cooling to be problematic, and most of us have suffered through some of them. The A4, especially RWC (raw water cooled) has known cooling failure modes, which is a good thing because the diagnosis and solutions are pretty straightforward, albeit not always cheap.

Follow the water, as Al suggests, starting from the inlet. With a cold engine, a 5 gallon bucket, and some extra hose (this is the perfect opportunity to replace ALL your hose, and if they're cracked, you should!):

1) Disconnect the inlet hose to the pump. Open the raw water valve. The result should be an alarming flow of clear water.

2) Reconnect the pump inlet hose. Disconnect the outlet hose and put a short length on the pump outlet to the bucket. Run the engine for 30 seconds - you should get a gallon or two tops (the pump is about 6GPM at full RPM IIRC).

2.5) You can skip this step initially, I would, but if #3 fails then you'll be back here and worse. Replace the hoses to the side plate/bypass loop. This will usually require swinging the alternator out of the way. The side plate and fittings are often badly corroded, and may mushroom into larger problems so tread lightly....

3) Remove the thermostat from the housing. Look inside while you're there for crap ('rust crispies', which are exactly what they sound like). Do you have a bypass loop? If yes, close it off. Put the thermostat housing back on and take the hose off the manifold end. Run the engine for 30 seconds - should be the same as in #2.

4) Reconnect the manifold hose, and disconnect the manifold to exhaust hose. Run again for 30 seconds. Should be the same as #2.

At every step, there may be a modest reduction in flow, but you're looking for a big difference. Very common problems in the order of which you hope for: time for a new pump impeller/cam, the thermostat, the rear outlet of the exhaust manifold catches a lot of crap, the block is getting plugged up.

A few things to report back: RWC or FWC? Bypass loop or not? Exhaust type? How is the water injected into the exhaust? Have you done an acid flush/vinegar soak?

Search the forum under 'cooling problems'. You are not the first to go down this path....

P.S. Be gentle with water from a hose into the engine.... City water may be 30-80 PSI, and that's a LOT of pressure for an engine that operates at basically zero.

[hanleyclifford]

I would begin at the manifold water exit. Take the hose and fitting off. This point is the most common clog culprit.

[zellerj]

careful if you have a plastic or fiberglass water lift muffler

Running the engine for 30 seconds without cooling water mixing with the exhaust may melt your muffler inlet if you have a plastic or fiberglass waterlift muffler. I would run it for just the minimum time needed to check the flow.

Learned this from experience.

Best,
Jim

[JOHN COOKSON]

. I ran bucket water through a hose to the engine, and water was not circulating, though the hose has cracks and i doubt the pump had a good seal for suction.

This won't help you find the clog but:
Did you prime the pump after you had it apart? Sometimes pumps need priming to start pulling water after they have been disassembled.

TRUE GRIT

[BunnyPlanet169]

I would begin at the manifold water exit. Take the hose and fitting off. This point is the most common clog culprit.

Not disagreeing, but it usually means there's more where that came from somewhere upstream.... You'll want to figure the full extent of any blockage as you figure remediation.

The comment to go FWC is the Holy Grail of A4 cooling. Any cooling saga (pilgrimage, Batan death march, epic, 'journey', etc....) should end with FWC. A 46 year old engine deserves no less.

[calebsurfs]

Thank you for all the replies. One thing I should mention is that the pump is off the engine and I'll need to get a new gasket for the impeller cover before I put it on again- the gasket was in rough shape and there was probably a bad seal.
There's plenty of water coming in through the raw water intake. I ran the hose water very lightly, so not a lot came out when I ran the engine with that, but there is approximately 0 coming out with raw water.
A few months ago i resealed the muffler inlet, and now there is a lot more water than there used to be in there. So I'll try to check for clogs there.
I disconnected the hose from the thermostat to the manifold and blew canned air each way. Lots of air to where the water pump connects and less through the manifold.

[Al Schober]

Keep in mind that the water pumps DO wear out. Impellers are a regular maintenance item, seals when the pump needs it, and occasionally a new shaft. But even with these repair parts, the bronze housing wears out and the pump is junk, just with a few new parts.
When I went to FW cooling, my old pump didn't do the job. Leaking a little sea water into the bilge is no biggie. Leaking coolant was a big problem (like losing blood) and I ended up with a new Moyer ball bearing pump.
In a pinch, I've used a piece of paper bag as a gasket. Smear a little blue silicone on the housing, slap the paper on and punch holes for the screws with a pencil, then a bit more blue silicone and slap on the cover & snug it down. Cut off the paper hanging out and don't worry about the paper inside - the impeller will make it go away. Buy me a beer and I'll tell you the story of the gaskets and the Fiat transmission...
Hard to blow through the manifold? Pull off the elbows and see what you see. Clogged outlet elbows are common. Another clog that I've experienced is at the thermostat - clogged with flakes of rust from the block. An additional area of known clogging is at the top of the block where the water flows into the head - correction of that requires removing the head, a hammer and a small screwdriver.

[JOHN COOKSON]

I would begin at the manifold water exit. Take the hose and fitting off. This point is the most common clog culprit.

I agree. Since this is a true unknown let's start by finding out if the engine's cooling system has a problem or if the problem is after the engine. As noted the manifold water exit is a common point for a clog, especially if there is a 90 degree fitting. After mine plugged up the second time I put a straight barb in it's place. No more plugging up.

TRUE GRIT

[calebsurfs]

Water flowing! But new problem

I'm happy to report that water is practically gushing from the exhaust outlet. It turns out the manifold was clogged and all it took was a few jabs with a screwdriver in the water outlet to clear the blockage. I also blew through the manifold with a shop vac and had plenty of flow.
After putting everything back together I ran the engine for 10-15 minutes. I had some water leaking out the cover of the water pump but it was working well. Now the problem is that the coolant water never got over 80 degrees (ocean is 60+ here in San Diego right now). So it looks like I've got to fix the thermostat, any suggestions for a quick fix? I'm happy with how the first repair turned out, the only expense was the beer I drank after fixing it.

[hanleyclifford]

I'm happy to report that water is practically gushing from the exhaust outlet. It turns out the manifold was clogged and all it took was a few jabs with a screwdriver in the water outlet to clear the blockage. I also blew through the manifold with a shop vac and had plenty of flow.
After putting everything back together I ran the engine for 10-15 minutes. I had some water leaking out the cover of the water pump but it was working well. Now the problem is that the coolant water never got over 80 degrees (ocean is 60+ here in San Diego right now). So it looks like I've got to fix the thermostat, any suggestions for a quick fix? I'm happy with how the first repair turned out, the only expense was the beer I drank after fixing it.

The thermostat is probably the source of your problem. Best play is to lose it and install a manual bypass; this is especially important for RWC engines.

[sastanley]

All of the above is good info, and I like Al's improvised gasket for the impeller plate..

Someone once said to me..."the best waterproof paper I know of is a dollar bill"..I don't condone ruining US currency, but in a pinch, it might be cheaper than a $3 gasket for the impeller plate.

Oh, and welcome! You people in San Diego enjoy year round boating (and obviously surfing!), while my cockpit is full of snow to the winches.

[JOHN COOKSON]

Corroded end terminals or resistance in the wiring sending unit ->gauge will cause the gauge to read abnormally low. If you need directions how to test put up a post or send me a PM.
Another possibility is KRAP around the sending unit in the port that it sits in which acts as an insulator. It happened to me on my A4.

TRUE GRIT

You really have a gauge that reads as low as 80*?
If so it makes me suspicious that the gauge and sending unit are mismatched.