New Cooling System on Perkins 4.236
Clark June 16th, 2016
This upgrade is common to all older Perkins diesels (the Perkins 4.108 is probably the most common Perkins found on boats). Bowman, the company that made the marinizing equipment for Perkins, has re-engineered things over the years, so that instead of having a combination header tank and heat exchanger on one part of the engine, and a water jacketed exhaust on another, they combine it all into a combination header tank/heat exchanger/exhaust manifold.
These engines were originally fitted with oil coolers. Now in some cases they say you can do away with the oil cooler unless your engine is run very hard. Since mine chugs away at about 1400 RPM cruising speed, I did away with the oil cooler.
At 50 years old, my old header tank was disintegrating (one surveyor took a very dim view of this), as was the heat exchanger stack, so that the whole business relied on a lot of polysulfide sealant and JB Weld. The old oil cooler failed spectacularly about five years ago, both blasting hot oil all around the engine room and filling the crank case with sea water. This is why one should always carry several oil change’s worth of oil at all times.
The first hurdle, and the only real engineering/fabrication part of the job is to modify the intake. If you look at the picture above, at the top of the picture you’ll see the air intake duct sticking out over the exhaust manifold. This would not do, as the new part would attach right there. The intake duct must be cut off and moved somewhere else. There are several ways to skin a cat, but I decided I wanted to keep my intake duct right in the middle, the way Perkins engineered it, but sticking up instead of out to one side.
I went off to my normal machinist/metal fabricator guy, to find a sign in his window saying he wasn’t taking any new work and would be closing up shop. I tried another place nearby, stood in the middle of his shop leaving him a voice mail, and never heard back. Found another metal fabrication place that was backed up four months. Left it at one place: They said they’d get it done the next week, didn’t, didn’t even bother to call me, then took off on vacation. I want back ready for battle, found the doors wide open, nobody home, and my parts sitting right where I’d left them two weeks before. I took my parts and my card and took my business across town. Is this telling me something? Should I be learning to weld? Is it just a Bay Area thing, or is it getting hard to find good tradesmen in this world?
At the second or third stage in this frustration I decided I’d go at it alone as much as I could, leaving only the welding to be done by a pro. The first step was to cut off the intake duct with a hack saw, which was satisfying and straightforward:
Then I went to www.onlinemetals.com and ordered a few pieces of stock, some aluminum tube to make the new duct, and some aluminum plate to cover the hole where the old duct had been. I used a 2-1/4-inch hole saw to drill down into the intake, making a home for the new duct. After a fair amount of cutting, sawing, and filing I had my pieces finished and ready for the welder:
Here are the old, tired bits that went away:
On top is the old exhaust manifold, which broke when I removed it. It was raw water cooled. The exhaust manifold on the new bit is fresh water cooled. Methinks this is a change for the better.
Here is the new bit, painted and ready for action:
There were many other little bits and bobs to source, customize, and fit. I had a brand new spare water pump, so I installed that while I was at it, replaced the transmission cooler for the same reasons as the heat exchanger, repainted where I could, and replaced all the engine hoses, as they were getting on twenty years. And I got one of those K and N washable air filters, since that’s what all the kids seem to be getting these days:
So far very happy with the modification. It did away with about fifty pounds of ancillary crap on the engine. Seriously, I’ve got a giant box of stuff, which I can barely lift, which is no longer needed, and this doesn’t even include the old header tank or exhaust manifold. And I’ve now got about another foot of space between the front side of the engine and the engine room bulkhead, which is great because the core of my electrical system is on this bulkhead.
The only problem is that she seems to run too cool. My wife asked, “Isn’t that good? You installed a new cooling system and now it runs really cool?” Excellent logic, but not exactly right. There’s a right temperature, which for Perkins is something like 160-180F on the cooling water. Mine seems to be barely tipping the gauge at about 120F. So now it’s off on a bay cruise with digital thermometer in hand to figure out if it’s an instrumentation problem or if she’s really running cool. Yes, I bought a new thermostat in case that’s all it is.
