The GTM Supercar Build Log

Coolant Line Ruptured, and Fixed.

Last week while cruising some back-roads in the GTM I started to smell coolant. Not the greatest smell when you are out in the  middle-of-nowhere and it’s blazing out. I came back into town keeping a close eye on the coolant temp and temps were still fine, so I took it out on some more back-roads with temps still fine, coolant still stinking, and eventually got it back home and on the lift. Suspicions were confirmed when I saw that the GTM had created a slow drip of coolant seeping through the underbody aluminum under the engine.

I took the underbody panel off and did not see anything out of the ordinary and assumed that the previously mentioned super slow coolant leak I had at the thermostat/steel hose connection was just seeping again. I then noticed some dirt on the water pump-to-radiator steel hose that runs in front of the balancer. Upon wiping the ‘dirt’ off I was sprayed in the face with coolant. Nice! Apparently the steel hose had chafed on the balancer somehow and it created a pinhole in the hose wall. Fortunately, I had dropped in some ’stop leak’ tablets into the coolant last week and that stuff clogged up the hole (hence the ‘dirt’ on the hose). I stopped the leak with some strategically applied paper towel and went to the local auto-parts store the next day and ordered new hoses to replace FFR’s supplied steel corrugated hosing. I ended up picking up Gates molded coolant hoses, part #’s 20827 and 20893, as per some recommendations from the forum.

To get started, I removed the interior engine cover and pulled the rest of the underbody aluminum off (tunnel pieces, at least). I started on the thermostat hose first and loosened up the 1.25″ hardline that goes to the t-stat steel hose. After draining what coolant I could from this side (about 2 gallons) I pulled the hose off of the t-stat and connected the Gates hose (20827). This Gates hose is a 1.5″ hose so this meant that it would not fit the 1.25″ hardline without an adapter. I mocked up the connection to the hardline and set to work on the water pump hose. This side dumped another 2 gallons of coolant, and then I disconnected the steel hose from the water pump. The Gates hose for the water pump (20893) is a 1.25″ hose, so it fit the water pump fine, but of course would not fit the 1.5″ hardline that it had previously connected with via the steel hose+adapter. As a result, I consulted with the forum again and decided to swap the hardlines side to side (not changing any connection paths, simply swapping the 1.5″ hardline with the 1.25″ line). This allowed the Gates hoses to fit up perfectly – 1.25″ from water pump to hardline, and 1.5″ from t-stat to hardline. No adapters, four less points of leakage/potential failure. The Gates water pump hose works quite a bit nicer than the corrugated hose as it clears the frame member in front of the motor, eliminating any possibility of it chafing on the balancer again.

With the hoses reconnected and hardlines secured again, I was able to dump almost 2 gallons of coolant back in. I jacked the front of the GTM up and let it sit overnight. The next day the coolant level dropped a ton and was able to get another gallon in. I started the GTM up and let it idle for a few minutes, then shut it down. This got coolant circulated and pushed a bunch of air out and allowed me to get the last gallon of coolant I had pulled out poured back in. I then idled the car for 20 minutes or so (took that long to get to its standard 210 degree operating temp in a 95 degree garage) and it showed no signs of overheating. Fans were coming on, going off, temps held solid. Good stuff.  Shut it down and topped off the surge tank again with another quart of coolant/water.  No leaks. This fix ended up being much less of a headache than I had anticipated.

Buttoned the car up and got the car out today for a hot (102 degrees in the sun) 20 mile drive with some spirited throttle work here and there and all systems checked out. Temps never went past 210, and it seemed to be running cooler by bit, even.  This is how FFR should have the coolant lines setup in the manual from the get-go.

One Response to “Coolant Line Ruptured, and Fixed.”

  1. ddebono Says:

    I have been wondering what kind of access you had to the front end of the engine. Now I see that you can get there through the waterfall. The engine looks very snug.

    It is also reassuring to see your lift. I have a four post Direct Lift scheduled for delivery and install this October, and I have similar sized garage.

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