308 not getting coolant to radiator. Ideas?

Driving my 1980 308 gts’i’ last night and noticed the temp hitting the midway point and thinking it was premature to do so as it was cool out. As it drove it ticked passed halfway and started to climb. Pulled it into garage before it hit the 3/4 mark. Fans not coming on. I put a jumper between the thermo switch in radiator. They still don’t come on even with A/C on, which is supposed to turn one on. Radiator seems cool. So, I’m thinking it must be a water pump or thermostat. My question is shouldn’t the fans of come on when I put a jumper on the two leads? I checked the fuses and replaced one of the fan relays but still they don’t come on. Should I try a new thermostat or thermal switch before trying to dig into the water pump? The pump seems to be turning and the belt is turning. Ideas? Tips? Thanks..

 

Get an IR thermometer gun from Harbor Freight.
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Make sure it's full of coolant. You might need to bleed the air out. Run it and measure the temps. The fans won't come on until at least 180 F at the radiator.

 

I’ve got that thermometer. I can tell the radiator isn’t hot with my hand though.

 

Getting over 195 on the dash gauge and the fans always come on somewhere just before halfway on the dash gauge. Only time one didn’t come on was years ago and it was so to a faulty relay. Neither are coming on here.

 

Bled the radiator screw as usual.

 

Perhaps the thermostat has failed.

 

Check fuses and wiring as they should always come on with a jumper at the switch.

That said, if your rad is not heating you don't have flow from the engine,
T stat stuck closed or possibly a big vapor lock in the piping???

Get the nose up and open the radiator bleed....

Failure pattern of the tstat is to go to like 240 and finally open...

 

Back to the thermos switch, they csn "cook" from going overtemp and never self heal, so go get one for an 81 VW Rabbit and slam it in there...

But, your problem is not the switch if a jumper does not fire at least one fan.

 

I think your right about that as the night it happened the radiator was hot so the thermostat must of opened. Just odd that both the switch and thermostat would go at same time. The drive the day before both were fine. I’ll go with the switch first. Hard to tell if I jumped it properly since one of the spade connector ends is facing down and has to be felt with the alligator clip end to clamp.

 

Thermostat is not opening so there is no flow to the radiator. R & R thermostat.

 

Thanks for the responses everyone. Any info on the right thermostat to use? Who sells them? I’ll do a search too but if anyone has the skinny that’d be great.

 

Ok. Got the thermometer going. Tested my tongue (94F). Drove car and like previously temp climbed off the Zero to mid way fast once it warmed up. At the 225 ish mark on the gauge I turned it off without the fans ever coming on. Temp readings were this: expansion tank 165. Top of thermostat cover 135. Metal pipe to front radiator ( in engine compartment) 140. Front bottom hose or radiator ( passenger side) 95. Exit hose at top of radiator 93. I purged air at thermostat and radiator bleed screw longer than normal and even allowed a little coolant foam to spew in a effort to get more air out. Noticed too that sitting at an angle (18 degree or so) on my driveway held the temp gauge at the midway point for about 5 minutes but as soon as I backed it out and got level it climbed again. Any more thoughts? Insight? Thanks..

 

The fans aren't going to run until you have at least 190 in the radiator. Keep running/bleeding/driving.

 

It seems to me you're chasing multiple problems, yet trying to solve problem A by investigating problem B.

You said in your first post, "Fans not coming on. I put a jumper between the thermo switch in radiator. They still don’t come on even with A/C on, which is supposed to turn one on."

This has absolutely nothing to do with the temperature of the coolant or thermostat. If the fans don't activate when jumped directly to power, you have an electrical problem. Until you solve this problem, the fans are never going to turn even if the coolant goes thermonuclear. So get the fans at least working when jumped, then move onto the coolant flow issue.

This is doubly-true for the right-side (AC) fan. If it doesn't turn when you hit the AC fan switch, your problem isn't the coolant or the thermostat or the overflow tank or a hose.

ricambiamerica.com

 

So, finally got the inner liner out to get access to the thermostat. After taking the bolts off the housing and loosening the hose clamps it won’t budge! What should I do to get the housing off? Image Unavailable, Please Login

 

Well, take the hose off. Then you'll have more access to work around the gasket and pull it off.

 

Ok after cutting the hose I got the housing off. I go to take thermostat out and it doesn’t want to come off. Is there a technique? Don’t want to pry or scratch around the seal. Should I try pulling with pliers or going around the seal with a plastic knife?

 

Does the rubber seal around it come out too as one piece or is the thermostat placed into the rubber ring?

 

The rubber seal and thermo are 2 separate pieces. Both pull off/out.

 

Got it out.

 

The eagle has landed!

 

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there are cross references for that thermo if you haven't got one already.

 

Test it in a pan of water on the stove. With a thermometer you should be able to watch when or if it opens. I always test thermostats before installing them. It's good insurance.