Friday, March 9, 2018

Cool it

Machines wear down, wear out, even self-destruct. The Rolling Steel Tent is approaching a quarter million miles, so it’s not just a matter of regular maintenance anymore. Now that the steering linkage has been refurbished, and a couple of electrical gizmos replaced, the cooling system is starting to call attention to itself.

I was waiting at a traffic light in Calexico when I noticed the water temperature was surprisingly high—about 225°, 230°. I had been loafing along flat Highway 98 after coasting down the mountains from Coyote’s Flying Saucer Retrievals and Repairs Service. The air temperature was about 75°. The coolant should’ve been a little below 210°. But after the light changed and I was moving again the temperature dropped to normal within a mile. The same thing has been happening whenever I come to a stop then take off again.

Okay, what is this a symptom of?

I checked the free and easy thing first: coolant level. It was down just a little after letting the van sit overnight. Not enough to cause the problem. I added about a quart of water. That left five other possibilities, presented here in order of increasing cost and difficulty:

The thermostat is one of the most primitive bits in vehicle engines. It depends on an expanding and contracting bead of wax to open and close the valve. It’s not an uncommon repair. And it’s just a matter of removing a couple of bolts and swapping the part—after removing enough stuff around the engine to get at it, which is (like all van engine repairs) a bigger chore. And there’s some coolant to drain and replace.

I checked them for leaks. There were none. Everything was dry.

You might not know what a fan clutch is or whether you have one. The fan used to be simply bolted to the front of engines, turning all the time the engine ran. It was effective but robbed a little engine power. So a temperature-sensitive clutch device was added between the engine and fan. That way the fan would only be powered when it was needed. Today, a lot of vehicles use electric fans—particularly front wheel drive cars where the engine is mounted sideways. Electrical sensors turn the fan(s) on and off as needed. The Rolling Steel Tent has a fan clutch, and it might not be engaging to turn the fan on. To diagnose this I’ll need to drive around, heat the engine up, then open the hood and see whether the fan is turning. It’s on today’s to-do list. Replacing it requires removing other things to get them out of the way. It’s probably within my skill set.

Water pumps wear out, pumping less and less effectively until they don’t pump at all. If that’s what has been happening, the increases in maximum temperature would’ve been inching up over a longer period of time (months?) rather than fairly suddenly. Unless a bearing seized, in which case the temperature would shoot up and stay up while the engine was running. This is a job I’d have a pro do because of all the access issues and the greater chance of me doing it wrong. (I destroyed the engine in the third-hand beater I drove in college because the water pump hadn’t been properly sealed when a previous owner replaced it.)

The radiator isn’t leaking, but it might be clogged with internal deposits and/or bugs and plant matter outside. I could have the radiator “boiled out,” but that only makes financial sense for old, rare radiators. Removing and replacing a radiator is easier than a water pump, and I could probably do it myself, but there’s still all that coolant to dispose of. I could probably do this myself if I had to.

As always, my fingers are crossed that the problem is at the cheaper end of the scale. Or that things will fix themselves.

I started the van for the first time today, drove a quarter mile out to the highway and headed into town. The temperature rose quickly. It was up to 230° within two miles. That wasn’t encouraging. Then, bing, the temperature started dropping just as quickly, as if the thermostat had suddenly opened. Things settled in at about 190°, which is the temperature most thermostats are supposed to open. I drove around some more and the temp stayed steady. A real test would’ve been to get out on the Interstate and blast up a good grade, but I held off, wanting to observe what else might happen. Things remained normal. So there’s a good chance it’s just a sticky, dying thermostat.

This video shows what it takes to get to the various cooling components on an Express/Savana. It's not rocket science, just tedious and a little frustrating.

I drove over 250 miles today, most of it 70 MPH on the Interstate, up some grades, and the needle on the temperature gauge never got over 200°. Everything seems to be back to normal—for now.


  1. Sounds like you are on the right track.
    A word of warning on the fan...if it comes to that. I replaced our fan last year (same vintage, make, and milage as yours), and the aftermarket one I chose is super loud when we are on the gas hard. Maybe a GM one would be quieter or maybe ours was assembled on a Monday or Friday. YMMV.

  2. Monitor the coolant level (engine cold) every day... sometimes with low level the engine wil tend to warm up, and the direct damaged part will be the engine head(s) because they will "dry" first...

    If coolant is vaporising (sp) probably the termostat is out of specs (old also) or part of the radiator is getting clogged, the overheat will convert the coolant o vapor, no need to have a bad hose...