1987 740 spilling coolant from radiator plug

Today I was sitting in a long line at a drive-through restaurant, like
30 minutes in 100F weather with the engine running and A/C going.

The temperature gauge never went above about 1/2 way on the dash, which
is the usual range for the car. When I parked the car I noticed
antifreeze spilling on the ground.

I opened the hood and the hoses were fine, but on the passenger side
near the top of the radiator is a plug with a large metal nut and a
plastic plug in the middle. It looks like an access point for the aux
fan thermoswitch.

Coolant was dripping from there. When I got home it did it again and so
I tightened the nut 1/8-1/4 turn and it stopped.

I took a short drive and it did it again. I am sure it was the long
idle that did this. Here is what I checked:

Both intake and outgoing coolant hoses were soft and flacid, I am
thinking the thermostat is opening. The overflow tank was fine, only
dripped down from max to min.

When I opened the overflow tank, there was pressure and it relieved
when I opened the cap.

Is this normal (but needs to be replaced) because it is a plug used to
fill a spot where a switch should be? Or should I be concerned?

Thanks,
Jamie

 

My first thought was what the hell were you thinking sitting in a drive
through for 1/2 hour? Park the car and walk into the restaurant....

The radiator cap is supposed to pop open or fail when there is too much
pressure in the radiator so I would think that it should be replaced if
it's old. I forget the PSI they blow at. So there is too much pressure
in the system and the coolant found the easiest way out.

Next time park the car in the lot and walk in...



Jabber 1999 S70.

 

Bad experience at the drive in. I was the only car there, waiting like
a dumb-ass, 35 minutes at the window of a local restaurant and ended up
still not getting my food and had to go inside for a refund.

At any rate, this could have been anywhere, maybe idling in rush hour
traffic - who knows?

The thing is that the temperature gauge didn't go very high and even
this morning after a short drive in cooler temperatures and the engine
warmed up - this plug was dripping.

I think that someone disconnected the Aux Fan, because the
thermo-switch is loose beside this plug. They put some plastic plug
inside the hole and I am wondering if it had no sealant, or if the
sealant failed.

This weekend I am going to pull the plug and reseal it with heat
resistant sealant.

I was mainly curious to know if this is common for these plugged holes
to leak.

Thanks!

 

I was thinking in terms of heat and not pressure, Jabber. I'll replace
the cap also, in case it is not releasing pressure. I should have
realized that when the overflow tank was pressurized.

JB

 

The same hole was filled with a "freeze plug" in mine, and the pplug came
out about a week after I go the radiator. I epoxied a plug in it and have
been happy since. As long as yours tightened down I think you have it fixed.

Mike

 

Still leaking through the plug hole, not the threads. I'll do epoxy and
maybe replace the cap.

Thanks.