308 cooling/thermo switch problems

A lot of issues there.

Yes, the drip can cause air to get in the system via the bleed valve.

Get it fixed correctly. Use tape only to get to a shop.

As for the fast idle and running hot, I sounds like you have a bad thermostat

 

Cap on the expansion tank is wrong too.

 

I don't know that cold idle system that well, but there must be a temp switch that is now broken, and needs replacement. Check this thread for valuable information from Rifledriver:

http://www.ferrarichat.com/forum/showthread.php?t=56204

 

If you mean the temp switch that screws into the radiator, DO NOT buy one from Ferrari or a Ferrari parts supplier. It is the same that is used in a VW from the early 80's. Pay $10 for that one instead. You can even buy a 180 degree switch to help cool things a bit better. No, your car will not run too cold or not heat up properly with the 180 in it. The fans will just kick on sooner - it won't KEEP the car below 180. I have had one in my 308 for nearly 8 years. It works perfectly.
The 180 switch can be found at most any aftermarket performance watercooled VW parts dealer. Do a web search and save some money.

 

Based on Rifledriver's comments, this would be a different thermo switch, located in the engine compartment. But not sure if it would be located on the rad expansion tank or perhaps on top of the engine...

 

Have you tried tweaking the valve a little tighter?

Are you using an auxiliary temp sensor to read the coolant temp; or are you relying on the cars temp gauge. The temp gauge or sensor may have gone south(not unusual). Are the fans coming on when the coolant reaches 195 degs. on the car's gauge; they should. If not, that may be an indication that the gauge or sensor is bad.

Take that 7 lb. cap off immediately, and replace it with the proper cap!

 

Ok I'm prepared to get jumped on .........What's so bad about a 7 lb. cap?

 

A 7lb cap will make the car run hotter, better to fit the correct value cap - 0.9 bar (13lb)

 

I'm not saying "no way" but am asking how it will run hotter? As I see it adding pressure raises the boiling point and doesn't add temperature to the coolant. Just plain water will boil at 212 deg. at 0 psig, at 7 psig it will boil at about 232 deg. and at 13 psig it will boil at around 245 deg. Adding anti-freeze will raise all the above boiling temps.
As a kid in hot Florida I ran my GM product for weeks without a radiator cap because I didn't have the $$ to fix a radiator leak and it never over heated.


SORRY Stevegtsi, there should be a small copper washer under the radiator bleed screw.

 

You can go down to your local hardware store and get a neoprene (rubber) washer to put under that radiator bleed screw and that will seal it up nicely without having to torque it down hard. It might cost you $.19

If the car is overheating, I suggest that you first check to be sure that the thermostat is working. When the car is warmed up, be sure that the radiator is actually getting nice and hot. That means that the thermostat (above the water pump in the engine compartment) is opening and allowing coolant to get to the radiator.

If the thing runs cool on the highway, but overheats in traffic, perhaps your cooling fans aren't coming on. Let it idle for a few minutes and watch. If they work, BOTH should come on. If only one comes on, you probably have a fusebox issue. (308s are notorious for the bad fusebox!) Each fan has its own fuse in the fusebox.

If both don't come on, it could still be a fusebox issue, but playing the law of averages, it's more likely to be an issue with the thermostatic switch in the radiator that switches on the fans. FYI, my (limited) experience has shown that usually the switch is not the culprit in this case, but the connectors. It gets hot, it's near the ground, it gets dirty and corroded, and the spade connectors don't make contact. Try cleaning them. I actually soldered "pigtails" on mine and put the connectors a foot away from the radiator, tucked safely up higher, and have had good success.

Birdman

 

I just had one fan rebuilt and it works fine but now the other (left) one doesn't come on. It works with external power. I'm testing by turning on AC. Am I wrong in assuming that should turn both fans on? Sorry for the probably dumb question.
Plastic 308

 

IIRC, only 1 308 water fan is energized with the AC function. If you remove each water fan relay and then touch a jumper wire from the 30 terminal to the 87 terminal of the relay socket (with the ignition key "on"), the corresponding water fan should run. Easiest method IMO if you're only interested in checking the fan motor function -- to do a larger functional check (relays and fan motors) you need to short the leads on the temp sensor in the bottom tank of the water radiator (with everything plugged in, of course, and key "on").
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91tr: Thanks ! That helps a lot.

 

Steve,
This is very helpful info to me right now as I try to figure out why my left fan is not coming on as temp reaches 195. It worked fine until I R & R'd my radiator to install new fans (hayden 3680s) onto my A/C condensor.
After re-filling the coolant and running the engine until warm, my left side fan does not come on. Right fan comes on OK with A/C. I tested left fan using your "relay short" method, came on fine. I'm going to short the connectors on the temp switch (bottom of the radiator) to see if the fan will come on. Does that neccessarily mean that the temp sensor internals still work?

Side note: my radiator is not getting warm, even though water temp gauge shows 195 temp.... I really doubt if the water pump thermostat went bad.....


Thanks,
Greg

 

I thought the currently recommended cap is the "four eared" version rated at 1.1 bar?

 

Greg -- If you short the wires at the thermal switch in the radiator together and both fans come "on" either:

1. the thermal switch itself is bad, or

2. hot water is not reaching it (system not well-bled, bad thermostat, blocked line, water pump impeller not turning, etc.)

Your description sound like #2 (i.e., when the engine is at 195 deg F, the water hose entering the top of the radiator should be quite warm). 1st thing to do is make sure it's well-bled -- which isn't easy on a '77. In '78 they even added another bleed port to the thermostat housing to make it easier to bleed. Try elevating the front end (i.e., get the bleed port on the radiator to be the highest point in the system) and filling/bleeding when running and radiator cap removed.

 

Steve,
I think it's #2. The radiator isn't even hot...

I shorted the thermal switch--both fans came on.

I put back the same amount of coolant that came out, so maybe I just didn't bleed enough air. I'll raise the front, but, should I continue to add coolant, even though I think the system's full? Does it take that step to push all the air out?

It's gotta be coolant flow.....

Thanks,
Greg

 

on the '80 gtsi, the fast idle is controlled by a temperature switch in the expansion tank. When the coolant is cold, the switch is "open". When the coolant gets hot, the switch "closes" (zero ohms resistance).

If you don't have an ohmeter, you can verify stuff is working by just shorting the two wires/connectors at the switch. Fast idle should immediately cut off.

The switch is controlling an electrovalve, which in turn gates the vacuum to a valve for an air path around the throttle plate. If the coolant tank switch is ok, then the electrovalve could be the cause of fast idle not dropping out. The vacuum controlled bypass valve is not likely to be a problem.

The car does not have an auxiliary air valve like the later 3x8 cars that progressively lowers the idle as the car warms up. The idle is obnoxiously high until the coolant is hot, then it drops instantly to normal. Search the archives for ways to lower the fast idle speed.

If you have no coolant flowing through the expansion tank, you will have a problem getting the switch to close. Run the car with the tank cap off to see if you have flow in the tank.

There is another switch in the expansion tank with vacuum lines on it. That one controls the egr valve.

 

Your engine will toss its coolant because the cap will release too soon.

Experienced this with my 328 not so long ago with a 6 year old cap gone bad. Tossed a gallon in fairly short order.

I.

 

walt p: you're absolutely correct; raising the coolant pressure advances the boiling point of water, it has no effect on heat transfer which determines the operating temperature. jon s.

 

OK, I can confirm that the coolant is pumping fine up to the radiator.

The thing is full. I test drove the car, and got it nice and warm. Fans still won't kick on at 195. I parked it immediately. Again, I shorted the 2 temp sensor wires and both fans spun right up. So, the radiator fan switch must be bad.

So, I went to Autozone and picked up the VW replacement. Part # SW 533.

Can anybody confirm the temp rating on this one? Carreaper says 180, which is fine by me; I prefer a little cooler threshold.

If my shorted leads spin the fans, isn't the only possibility a bad radiator temp switch?

Gregg

 

bump.....

 

The factory one has the fans coming on at 190 - 195 ish so 180 is fine, 160 wuld probably be good also but a properly functioning 308 cooling system works well with the stiock part even here in hell ( aka south Louisiana) in July

 

I'm with Frank on this one -- my stock ex-'78 308 cooling system never gave me any trouble (without actually counting, my impression is that most of the trouble reports here are for the later 308s).

Greg -- A 160 deg fan switch is going to make virtually no difference in a system with a 176~185 deg thermostat. The "number" F gives in the carbed OMs is 183 deg for the radiator fan switch closing so the 180 deg one you've got is A-OK IMO -- why not try having two working fans and see how it goes before resorting to any further gymnastics