[Duke58]

What am I doing wrong- when I remove the vent screw on the throttle body, coolant does not come out. Looking at the system, the upper radiator hose is above the thermostat which is normally closed when the engine is cold.

Is this procedure supposed to be done with the engine warmed-up (thermostat open)?

 

[ghnl]

There should be a small hole in the thermostat to allow air (& a small amount of coolant) to pass by even when the t-stat is closed. It is possible the wrong t-stat is installed (one lacking the typical bleed hole) or the hole is blocked (malpositioned gasket or gobs of RTV sealant were applied).

Starting the engine and letting it warm up enough to open the t-stat should get the last bit of air out. Just becareful not to burn yourself...

Instructions from IAP tech page.

 

[Duke58]

Thanks, Eric.

Now the vent screw is cracked and leaking- anyone know what size the thread is? Is it M14 X 2?

 

[Duke58]

I guess no one ever needed a vent screw?

Its okay- I machined a washer out of brass which solved the problem...

There is no way that I can see where filling the radiator and removing the vent screw will ever result in coolant to flow out without the engine running. The vent screw is higher than the radiator on the 1986 Spider, and even with the vent hole on the t-stat, there isn't enough head pressure to cause the coolant to flow up to the vent screw. Only way possible I could see is if the car sits at an angle with the vent screw lower than the radiator- a pretty steep angle.

I warmed the engine to 180 degrees F, revved the engine until coolant flowed out of the vent screw and tightened. Seems to have done the trick, but if its anything like the rest of my obsessive/manic depressive-like routines, I'll most likely take the car for a long test drive and check everyday for a week.

This all started while driving to work and I noticed the car was running hot. These were the original factory hoses! Car has about 140,000 miles. I drive it everyday. When I pulled into the parking lot and turned off the engine, I could hear a hissing sound, popped the hood and saw coolant spewing out of the lower t-stat to water pump hose. I changed the hose in the parking lot and smelled fuel from the number 1 cylinder fuel rail position. It took a couple hours to remove the fuel rail in the parking lot, called my wife to pick me up, then dropped the fuel rail off at the local Alfa mechanic's home for a rebuild, and thanked God that it didn't start leaking while driving and explode/burn up my car. Next afternoon, I installed the rebuilt fuel rail with correct material/size hoses and had her running in an hour.

So, what's the difference running a lower t-stat hose without the brass restrictor in the hose?

 

[ghnl]

Discussion of coolant bypass restrictor

 

[Duke58]

Well...I don't really call that a discussion...a discussion means other people tell about their experience, how they solved the problem.

I'll just have to drive the car myself and find out! Then MAYBE I'll post on the BB here...depends on if I get irritated, pissed off by someone's posting, the phase of the moon, testosterone level.

 

[ghnl]

OK, that was just the one reply in the discussion...

 

[Duke58]

No one has ever needed a vent screw...

 

[Duke58]

1986 Graduate: I spent a couple hours this afternoon driving the car, and it did run hotter- about 194 degrees F vs. 175 F as usual. SO- I took the bypass restrictor (discussed in a discussion linked above), off the old hose and installed it on the knew one. So far, the car runs fine at just a hair above 175 on the gauge (not real accurate). However, Tifosi was correct in his discussion that the car runs hotter without the restrictor.

As for the vent screw- I machined a washer from brass and it no longer leaks. I'll figure out what screw size it is and machine another at some point in time.

Will Vaseline affect the hoses? As they say in chemistry: like dissolves like...I'm buying another set of hoses just in case.

Looks like I won't have to take the bus at all next week. Getting a beer right now.

Thanks for all the help, ghnl.

 

[ghnl]

Not sure about vaseline. I prefer to use rubber lubricant.

OK, get your mind out of the gutter, not that kind of rubber lubricant - this kind: