Frank_Blotto

So I finally got the 'maro running, and it ran great but it was r running a little too hot. So I took it home, and when I parked it, it blew out right behind the top radiator hose. Scared the **** outta me. So I believe that the fan swtich is bad, since the fan wasn't running as far as I could tell. I understand this is a fairly common problem with 305s. Think the radiator could have been clogged or something. Anyways, I need a new radiator, anyone have a good suggestion, I'm on kind of a budget. Thanks folks!

Rick King

Maybe you can have yours flushed and rebuilt. they can put new tanks on them


later

rick

Frank_Blotto

hmmmm, that never occured to me. Would it cost less than buying a new one from Jegs for $180? What kind of shop would you go to get that done? thanks for the quick response!

Stekman

If this is a simple LG4, a direct replacement from Autozone or Napa would be the best bet. I beleive Napa sells Modine replacements. Not sure who makes Autozone's. They're about $120 IIRC. Aluminum cores, too.

Frank_Blotto

Ok, not bad. I think I'll head over to Napa. Anyone have any idea what would have made it blow up in the first place? The engine temp wasn't that high, maybe 240 tops, and I only drove for a grand total of 10 minutes. But I'm sure the fan wasn't working...

Frank_Blotto

Anyone? What would cause my radiator to blow out like that? Rust? Sediment? Old coolant? It was mostly sitting for about a year.

todd200

240* is kinda warm. If the fan wasn't on the system pressure probably got high enough that it took out the weakest spot in the radiator. Replace it, find out why the fan isn't working, and flush the system.

Frank_Blotto

Ok. That was basically my plan. I'm gonna replace the fan swtich and relay (they are two differnent pieces, right?) as well as the radiator and hoses. Then I guess I'll have to test the fan motor without the engine on, and work from there. Thanks for your input.

78camaroz28

Funny...the same thing just happened to me with my 86 T/A last week. Car overheated before I realized the fan hadn't come on. I shut it down and seconds after I walked past the open hood, the left side of the radiator blew sending plastic and steam sky high. A new (stock) radiator only cost me $117 at the local radiator shop. At that price, it wasn't really worth having the old one rebuilt.

Frank_Blotto

Wow, how ironic. Did it scare the hell out of you too? Where I live, everyone wants 160 for a stock radiator! So annoying...

Oh yeah, my hood was closed though, ripped a nice big chunk out of my hood "insulation".

78camaroz28

It scared the hell out of me! The blast was enough to shake the shelves in my garage.
$160? I only paid $140 for a new radiator from the local GM dealer for my 92 RS when I was in Germany...must be the price for living in CA.

Frank_Blotto

Ok, I got my new radiator installed (yay!) as well as a new fan switch. But I still can't figure out my fan dilemma. I ran the wire from the fan swtich to my positive terminal and the relay clicked away, but the fan didn't spin. I'd interpret this to mean either bad wiring somewhere, or a bad fan motor, is that correct? I think i'm gonna "engage" the fan again and test for voltage...

Frank_Blotto

Hrm, what would be the best way to test if my fan is actually capable of spinning at all? Would I run the wires from the fan to the positive terminal on the battery? They just disappear into the harness fairly quickly, any ideas?

91Z28-350

I believe it is grounding the wire that goes to the fan switch to energize the relay, not connecting it to battery positive. Fan switches ground the wire through the engine block.

You're going to need to check the relay. I don't know which terminals to jump, but you can do some basics based on the size of the wire. Trickster probably has the manual for your car, so he'll probably post the diagnostics for you.

In the mean time, check the wires going to the relay. To do that you can pull out the relay from it's socket and use the probe on the socket. OK, there should be 4 wires going to the relay. An orange which is hot at all times (battery positive). There should be another fat wire (don't know the color because no manual). It may be striped with a base color of black. That is the wire running to the fan. There should be 2 smaller wires. One is ignition hot. The other is going to the fan switch.

OK, got all that? Now, take your multimeter. Set it to measure DC voltage. Take the black wire on the multimeter and connect it to battery ground (usually long wires with multimeters), if not, ground it on the alternator bracket or some other ground nearby.

1) Take the red wire on your multimeter and probe the pin where the Orange wire is. That should read battery positive with ignition OFF.

2) Turn ON the ignition and probe the smaller wires. One of them should read battery positive also. Note which one it is. If not, there's a problem with the ignition on feed to the relay. This is used as the opposite for the fan switch. Remember the fan switch grounds, and the ground completes the circuit and actuates the relay, connecting the 2 fat wires and turns on the fan.

3) OK, now take a piece of 10 gauge wire. Strip the ends off and through the socket, connect the 2 fat wires together using the wire. The fan should spin. If not, the fan motor can be blown, or the wire to the fan is cut off somewhere. The other posibility is that on the fan, one wire runs to ground...that ground could be bad. If it spins, continue on.

3a) If the fan doesn't spin, pull the connector out of the fan. Probe one wire to make sure it is connected to ground. The other wire will just have floating values indicating it is not connected. Take your multimeter and set it to check resistance or continuity. Connect one end to the floating side of the switch (it should be the same color wire as the one coming out of the relay). Connect the other end of the multimeter to the fat wire in the relay socket that is NOT hot (not Orange). Resistance should be low, or continuity should be found. If good, continue on. If bad, the wire to the fan is cut, you can continue on to find out what else is wrong.

4) Set your multimeter to measure resistance or continuity. Place one end of the multimeter's terminal on the fan switch wire. Place the other end on the small wire that is NOT ignition hot. The resistance should be very low, 1 ohm or less. If not, make sure you are on the proper small wire. If still not, you may have a cut wire. Note that down and continue on.

5) This part is a bit tricky. Put the relay back in the socket. Now that you know which small wire is ignition not, and which small wire is NOT, you can make sure the ignition is on and then run ground into that terminal point (the small wire which is NOT ignition hot). The relay should click and the fans should turn on. If so, continue, if not, double check what you did. If all is correct, replace the relay.

6) Once the relay is replaced, verify step 5 again. Once that's good, ground the fan switch wire to double check what you found in step 4. If you measured no continuity or very high resistance, you are expecting the wire to be cut, but this is just triple checking. If it doesn't turn on, find where the wire is separated. If it does, all is good.

7) Plug it into the fan switch and turn on the engine and let it heat up. If after a long while and engine hot (don't let it overheat), and the fan doesn't turn on, replace your fan switch.