H2

I'm still running a bit on the hot side and about that's left as suspects would be a gunked up and restricted radiator or possibly timing issues or lean/rich injectors. I think everything else has been tested,

For testing the radiator, why couldn't I just duct tape a water hose to the top radiator hose and open the bottom radiator hose up and eye-ball the inflow/outflow to see if it appears to be about the same?

BTW, all exhausts test at about 300 or so degrees at the manifold as it exits the engine block, except two rear ones on passenger side, which appear to be running hotter at about 500 degrees but it could be the way I'm pointing the temp sensor. If measurements are accurate what would cause this?

Harvey

shaaark89

harvey,
unless there's a hole in the radiator, the inflow and outflow would have to be the same. it would be interesting to measure the backpressure at the intake side to see how much restriction to flow might exist. either of these tests still won't tell you whether all the passages are clear as the flow will go to where it passes easiest.

dr bob

Harvey--

If it's the original radiator with no history of repair/clean/etc, it's undoubtedly due for a little work. If the end tanks have never been removed (look at the tabs and see if the paint is still perfect) then now would be a good time to replace them anyway, and an opportunity to have the core cleaned or at least inspected.

Radiators will gather precipitate in the bottom tubes unless they are treated to great coolant all the time and are 'blown down' regularly to get that stuff out. Getting that stuff out requires a pretty fair velocity of water, and is of course done most effectively when the radioator and coolant are at full temperature. Same as "it never gets done" since it's a dangerous chore at best. So the next best option is to pull the tanks off and clean the tubes from the ends. This is often done as a chemical cleaning, with metals tapes that are puched through the insides of teh tubes to dislodge the big chunks. The insides of the tubes are often rough finished or have inner fins on them, precluding the 'rodding' technique used in some very old radiators. A good chemical cleaning will get most scale and precipitate out, but at the expense of some of the tubing metal. The chemicals are obviously corrosive, and they tend to gather behind o-ring seals and in pockets where they may not be completely removed, so the cleaning is best done with tanks off. New o-rings at minimum, new tanks best when reassembling.

Many of us "experts" forget sometimes that there are other experts available, specialists that hang out at better radiator shops. They do this stuff all day long, and they get pretty good at it. Consider pulling your radiator out and taking it to your local specialist. They can test the thing for flow restriction, and may have a borescope so you can look inside through the hose nozzles down though a few lower tubes to get an idea how clean it is inside. That same shop will have the tools and clamping fixture needed to replace the seals and tanks. Worst case is that you'll need a new radiator, maybe a replacement Behr or one of the pretty all-aluminum pieces from 928 Int'l. But a pro inspection is usually free or cheap, so it's worth a look.

Every spring and summer there's a flurry of posts on running hot. Each spring, our cars have aged another year and another year's worth of crud has made its way into the radiator. At some point all the extra capaicity designed into the system, the safety headroom, will be used up, and we start to see the gauge moving hotter and hotter. It's a gradual deterioration that we often don't notice until the symptom is pretty severe. A good thermostat hides the symptom, right?


Since you have an IR thermometer now, you might consider a little experiment-- Pull the fan console out, and reattach all the hoses so you can safely start the engine. Let it idle and warm up but not to the point of overheating. As the water circulates, you can shoot the rear surface of the radiator to see a temperature profile. Even partially-obstructed tubes will be colder that those flowing more coolant. There's a very slight convection that's usually overcome by the velocity of the water flowing inside, but at idle you may notice it. The plugged tubes at the bottom will be noticeably colder in the middle.



This reminds me-- It's two years since I last replaced my five-year coolant, so a flush-and-fill needs to get onto the immediate maintenance schedule. I have the coolant already, just need to stock up on distilled water and a bottle of Water Wetter for the refill. Oil change time too. Looks like the jack and the stands are going to get a workout! And I'll probably get a bath...