Ya I used distilled water. It overheats mostly when I have the heater on, which is weirdddd. I'm thinkin a short in some wires or something.

Hey folks, did these subies come with those vacuum valves that turn off coolant flow to the core whenever it's not in use? Mine doesn't have one and the hoses are hot all the time regardless of where my heater control is.

 

So what would make his gauge raise up if there is coolant flowing through the core all the time?

Ya Mine are hot all the time too... unless those valves dont work.

Does the gauge rise if you just move the selector lever to HOT and don't turn on the fan? Maybe it's some fan related electical gremlin.

 

Still the exact same situation I had with my van, the heater sometimes (not always) would make the gauge rise up when I turned it on full-blast. It should do the exact opposite. who knows!

 

Oh, did you try the thermometer in the radiator thing? It would tell you one way or the other. If you can't get it to overheat at idle you could drive it around until it got hot then park and leave it running and CAREFULLY pull off the radiator cap with a thick towel, then put a thermometer in there, it should show you the temp when the gauge is showing hot.

Is it boiling over when it overheats at the guage?

Ya I used distilled water. It overheats mostly when I have the heater on, which is weirdddd. I'm thinkin a short in some wires or something.

 

Is it boiling over into the over flow tank when it over heats?

 

If you suspect the guage you can pick up a cheap mechanical one.

No boiling or anything, the overflow container coolant is ok to touch even, not that hot. Ya I might try a new guage and sending unit. Thanks.

I fixed my problem. The radiator cap was at fault. It wasn't making the system pressurize, so therefore it always boiled at 212. Normal op temp on must engines is round 200-210, so right on the verge of boiling. The boilinf temp rises 3 degs for ever PSI, so a 15 lb. cap takes the boil over temp up to 255ish. It doesn't boil over any more w/ the new cap. Yay!

So where was it boiling, into the overflow container? After you shut the engine off?

Ok I drove it to work this morning, and again it "overheated" when I had the heater on on the freeway. I got to work and popped the hood and the rad cap was not even warm, let alone hot. No boiling or anyting in the overflow container. The 2 heater core hoses were nice and hot though, so I dont know wats up. That definitly tells me that the engine is not really overheating. In fact it might even be running pretty cool since I'm still hardly getting any heat in the cabin when i have it on full blast. I'm gonna get a new rad cap today and maybe new sending unit.

Did you try what was suggested earlier. Running a feed back loop on the heater hoses and bypassing the heater core. Then seeing if it still overheats. Just run the hose from the inlet to outlet pipes on the engine.

 

Heatercore might still be plugged up somewhat.

Well I dont think it is overheating like i said, since the rad cap isnt even warm after freeway driving. Would a clogged up HC cause overheating?

Well I dont think it is overheating like i said, since the rad cap isnt even warm after freeway driving. Would a clogged up HC cause overheating?

 

It could, yes.

Hey 91Royale, what PSI cap did you get? That might be my problem too.

How long is your drive to work?

Its 1/2 hr, mostly freeway, some city too.

I don't know if someone already suggested this, but I would buy a mechanical temperature gauge, and JB weld the sensor to the top of the engine block. Then at least you know if the engine is getting too hot or not. I did this after my gauge went bad, followed by the thermostat, causing me to overheat the engine to the point of dripping oil out of seals and blowing the head gasket by the time I knew it.

Hmm weld it? Isnt the sensor supposed to be in contact with the coolant?

I would still lean toward a plugged up radiator. It's the most common cooling problem with these. In your case it sounds to me like it's plugged in such a fashion that you aren't getting good crossflow to the tank with the lower (outlet) hose. That's why the cap isn't getting hot. My bet is that due to the radiator being plugged you get an air bubble in the thermostat housing, which is also the location of the temp sensor. This causes a lower than actual temp guage reading, until you get some flow through the heater core which sends some coolant to the intake manifold near the thermostat housing. This gives the sensor some coolant to "feel" and gives you an increase in the temp guage. I'd say physically clean or change the radiator. It's probably already overheated more than you realize, but you may still save it.

Hm ya maybe. So what do they do when they clean a radiator professionally?

Hmm weld it? Isnt the sensor supposed to be in contact with the coolant?

 

Yeah, ideally. But I figured that what was important was the temperature of the engine block, because that is what has problems and blows out head gaskets when it gets too hot. By gluing it on with JB weld it should give a pretty accurate picture of the temperature of the block. And it is supposed to withstand up to 400F itself. I usually measured between 190 and 220 for block temperature when it was running properly.

 

Of course, you could also figure out how to put the mechanical gauge in the port where the old temperature sending unit was. I was just too lazy to do this....

Hi I was poking my nose in here for old times sake, and i had the same issue with my 88 Subaru. I replaced the radiator (totally clogged) and the problem went away. www.radiator.com had one for about 100.00 a few years ago.

The radiator gets cloged with gunk, old fluid slime, and the residue from using tap water in an aluminum engine as opposed to deminerilized water. I would not use a chemical flush at this time, or any time. That rust is holding together your radiator and your heatercore. your heater core has a much larger passageway then the radiator core. In fact a chemical flush can also remove the rust holding together your heater core too.

 

nipper

When they clean one at a radiator shop they will pull the tanks off both ends and clean all the build up off the exposed surfaces. Then they clean out the passages with a rod or wire brush (hence the term, having your radiator "rodded"). Then they should pressure check it to see if there are any small leaks in the solder joints and fix those. They'll reinstall the tanks and pressure check everything again. Should be nearly as good as new when done.

 

Note: Because coolant and metal store and dissipate heat at different rates, you will not get the same temp reading from a sensor glued to the engine as you will from one in the coolant.

 

Hm ya maybe. So what do they do when they clean a radiator professionally?

You'll spend as much getting it rodded and brazed as you will buying a new $100 radiator

Have to agree with Morgan. Unless you want to take a chance and try cleaning it yourself, you're better off to just buy a new or rebuilt one. Personally, as long as I had another ride just in case it leaks when I put it back together, I'd try cleaning it. It only costs you some time.