Diagnosis and Repair of Your Imperial's Engine Water Leaks

Imperial Homepage -> Repair -> Engine -> Water Leaks

Tips on diagnosing where you engine's water leak is:

There are two tests: the air pressure test and the water pressure test.

The air pressure test is:

Before you perform the air pressure test, make sure you completely strip and clean the block. Then, follow these basic procedures:

1. Seal all of the blockís freshwater passages with gaskets and flanges.

2. Connect a low-pressure air hose to a fixture on one of the flanges.

3. Immerse the block into a tank of water heated to the engineís normal operating temperature. Allow the engine to soak for approximately 20 to 40 minutes, as specified by the manufacturer. This allows the block to warm to the temperature of the water.

4. Apply approximately 40 PSI of pressure to the block and watch for bubbles. Bubbles indicate a crack or leak in the block. Determine what repair is needed or can be made when you identify the source of the bubbles.

If you cannot dip the block, you may still perform the air pressure test. Attach the hose to a fixture secured to an opening to the water jacket. Pressurize the water jacket. Carefully spray soapy water over the block and look for air bubbles caused by the pressurized air.

The water pressure test is:

The water pressure test is similar to the air pressure test, except that defects are indicated by water leaks rather than by air leaks. Before you perform the water pressure test, strip and clean the block Then, follow these procedures:

1. Seal off all but one of the freshwater openings with flanges and gaskets. Make seals airtight.

2. Fill the water jacket with fresh water until all air is purged from the water jacket. Seal the fill opening with a flange that contains an air hose coupling.

3. Attach an air hose and pressurize the water jacket to approximately 40 PSI (see the manufacturerís manual). Maintain the pressure in the water jacket for at least 2 hours.

4. Inspect the cylinder bores, air box, oil passages, crankcase, and cylinder block exterior for the presence of water. The presence of water at any of these locations indicates that the water jacket has one or more defects.


Engine gaskets must not be intermixed. Using the wrong head gasket will result in compression and or water leaks, therefore if you have a water leak, you might have the wrong or damaged cylinder head gasket.

Question from John (440):

While at the trans shop trying to figure out why my '65 wouldn't shift right,  the mechanic and I noticed coolant dripping fairly steadily. Instead of a hose or something, it was seeping out of the side of the block, on the left side, roughly 5 or 6 inches above the oil pan, and roughly in a vertical line with the oil filler cap. shit. Of course, the transmission guy (something of an alarmist) immediately said I need a brand new engine block, but my machinist and mechanic both highly recommend Aluma-Seal in the radiator to plug up a leak like that more or less permanently. Failing that, the machinist suggested cleaning the area down to bare metal with a burr grinder and sealing it with epoxy, which he says is a common repair to newer iron blocks that aren't nearly as heavy as a 413 and are prone to cracks & leaks. Now, this has apparently only been actively leaking for a few weeks (I'd noticed coolant on the ground, but thought it was from another car). I live in Tucson, and the coldest it's been since I've owned the car is in the mid-20s. Of course I have the right coolant/water mix, so there is no way it froze! Nor have I overheated the engine, but no telling what happened to it before I owned it. Why would such a leak just start now? If it's a crack, it must have been there for years, I am told. Maybe someone had sealed it before and it opened up again? The trans guy suggested it basically rusted through from the inside, but neither my mechanic or machinist thought so, having never seen such a heavy block just rust out. OK, my question is: what would you do? Financially, I am NOT in a position to pull and rebuild the engine, get a new block, etc. Is it doomed or is this a minor thing?


From Dan:

The first thing you should have checked are the freeze plugs. In case you didn't know, freeze plugs are found both in the heads and on either side of the block between the oil pan the the deck (where the heads attach).   Their purpose is to pop out in case the water in the block freezes so it won't crack (water expands when freezing and will crack the block if it doesn't have anywhere to go).   It's not uncommon for these to develop leaks, rust through, of just fall out.  I would take the car somewhere and have it put up on a lift where they can be checked. if they need to be replaced, (usually 3 per side) try to find brass plugs rather than steel, they hold up better.  This is probably all that is wrong with your car.

From Jim:

How about the drain valve on the side of the engine? If the leak is coming from behind the exhaust manifold, it may be difficult to see easily. Or how about the head gasket? Is there coolant in the oil? Does the exhaust have a sweet smell? It seems unlikely that the block would be cracked or corroded. I would try a good stop leak (Dike is my favorite, from Conklin) and see what happens. The prospect of removing the engine is not appealing, and I would want to be pretty confident that it is necessary before loosening the first bolt.

From Joe:

Don't forget to check for freeze plugs being rusted through. Many of these are hard to see with accessories and manifolds in place. I have had several of these fail of Chrysler products over the years. There are helpful replacements with a design which is basically two large flat washers with a rubber doughnut between them and a bolt & nut with lockwasher. Remove the old freeze plug and slip the replacement in place and tighten the nut. These are available at most car parts stores.

From George:

Personally, I never cared much for the canned block sealers. I was always afraid they would seal up something else, such as the heater core! Plus, the permanence of such repairs is iffy. Of course, the best repair would be to replace the leaking part. First, I would have the cooling system pressure tested to be as certain as I could of where the leak is coming from. It may be just a rusted out freeze plug, which can be replaced without engine removal. There are 2 types of replacement plugs, the original all steel disc type, which have to be driven in to swell them after removing the old one. The other type is a steel disc with a rubber plug, much on the principle of a boat transom drain plug, but instead of a lever to flip over to swell the rubber part and make it tight, there is a nut to tighten to swell the rubber part. This kind is much easier to install in tight places. Simply stick it in the hole, and tighten the nut until the plug is good and snug. If it turns out to be a external crack in the block, the epoxy method is an acceptable repair, depending on location and severity of the crack. The product named J&B Weld, available at all auto parts stores, has a very good reputation for patching cracks in most anything. Gaining good access and following the directions exactly would probably make a permanent, good repair. Cleaning the crack and surrounding area completely is essential! But, if the engine is a little tired, now may be the time to yank it out and give it what it really needs-----

This page last updated March 9, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club