1975 Spider overheating

NW75spider · Post by **NW75spider** » Wed Jul 26, 2006 11:28 pm

Ok, I know this has been asked a million times, but even after reading prior posts, doing searches outside the site, etc. I cannot figure out the problem.

I followed the instructions on filling the coolant system: disconnecting the hose from the tee that connects to the thermostat and using this hose to fill the system.

I drove the car for a short bit, and it quickly started overheating. I made sure the coolant level was correct, created a jumper to make sure the cooling fan comes on (it does).

After I shut her down, I very carefully touched the coolant system hoses to see if all were hot. The top two hoses were hot, as was the hose from the thermostat to the water pump. BUT, the hose from the bottom of the thermostat to the bottom of the radiator was cold.

The thermostat is brand new, so if that is the problem area, then either I have the thermostat installed wrong, or it is faulty.

HELP!

So Cal Mark · Post by **So Cal Mark** » Thu Jul 27, 2006 10:24 am

if the lower hose is cool, the t-stat isn't opening, and it won't open if there is air in the system. The air bubble gets trapped in the stat and prevents the hot water from contacting the sensor. I've found the best way to get the air out is to remove one of the small hoses from the choke housing and finish filling the system thru that hose.
Jumpering the fan switch won't bring the temp down since the water isn't circulating thru the radiator.

NW75spider · Post by **NW75spider** » Thu Jul 27, 2006 11:01 am

Thanks Mark.

When filling through one of the choke housing hoses, do you keep something open to let air escape?

So Cal Mark · Post by **So Cal Mark** » Thu Jul 27, 2006 12:58 pm

the air will escape thru the nipple on the choke housing, so put the rad cap on and have the rest of the system closed. When you get a steady stream of water coming from the choke nipple, reinstall the hose. Start the car and let it idle until the fan cycles, also put the heater on so water circulates thru it in case there is air in the heater core

NW75spider · Post by **NW75spider** » Thu Jul 27, 2006 1:27 pm

Thanks again Mark. I will give that a shot this evening after work.

NW75spider · Post by **NW75spider** » Fri Jul 28, 2006 12:48 am

Ok, I tried the process twice and either there is still a bubble, or there is another problem. Could someone verify I have my thermostat install properly? Seems like a silly thing to ask, but when I bought it from IAP it did not come with install instructions, and the unit I had before was very different looking. So, here is an image. Let me know if it is correct or not.

Thanks.

So Cal Mark · Post by **So Cal Mark** » Fri Jul 28, 2006 1:11 am

I'll have to look at one in the morning, but as I recall the leg with the machining goes toward the water pump

racydave · Post by **racydave** » Fri Jul 28, 2006 6:31 pm

my 79 is exactly the same as in your pic, I bled mine thru choke hoses.

NW75spider · Post by **NW75spider** » Fri Jul 28, 2006 7:04 pm

Thanks Dave.

NW75spider · Post by **NW75spider** » Wed Aug 02, 2006 11:19 pm

Finally got rid of all the air!

It took four or five times of pouring coolant through the small choke hose, but it finally works.

Very nice to be able to drive down and get some gas without the temp gauge getting too high.

Now I just need new tires, new top, seat belts, etc. etc. etc.

mbouse · Post by **mbouse** » Thu Aug 03, 2006 8:18 am

Just out of curiosity, when you were attempting to bleed and add coolant....

I did not read that you did a minor, but important step; so I have to wonder if maybe you forgot to do it, or just forgot to mention it.

That is, get the nose of the car as high into the air as you possibly can. And I mean, park on an incline, use ramps or jack stands to get that rear bumper and tailpipe almost dragging on the ground.

The whole issue with Spider coolant systems is that the radiator neck is not the highest point in the system, causing bubbles to get trapped. The higher the rad neck is in the air, the less room there is in the balance of the system for air bubbles.

This procedure is frustrating, even for the experienced Spider owner. I've owned mine for 11+ years, and still don't get it right every time.

So Cal Mark · Post by **So Cal Mark** » Thu Aug 03, 2006 9:56 am

that's why I suggest using the choke hose to finish filling the system-that's the high point. Adding a fill/flush tee to the heater hose over the cam cover accomplishes the same thing

NW75spider · Post by **NW75spider** » Thu Aug 03, 2006 11:00 am

When I initially filled the system, I did not have it on an incline.

When I did the bleeding, I was parked on my driveway which has a really good slope and had her nose down making the choke hose even higher than normal.

I probably could have saved some headache by filling it with the radiator neck at it's highest, then bleeding like I did. I will have to file that away for next time.

mbouse · Post by **mbouse** » Thu Aug 03, 2006 12:52 pm

Never heard of nose down method.

Lots of folks (myself included) attempt the level plane approach the first couple of times.

send me an email and I will send you Chris Obert's write up of the "best" procedure.

put "bleed coolant" in the subject line

mdrburchette · Post by **mdrburchette** » Thu Aug 03, 2006 7:52 pm

I don't think I even have a choke hose, do I?

I've had good luck with jacking the front end up, opening the heater valve and squeezing the hoses to force the air bubbles out.