Running Hot / Coolant Woes - 2003-04 Mach 1 Registry Owners Club

USMCWeatherMan · 02-27-2017, 04:43 PM

So twice before I had issues that first presented themselves as overheating leading to diagnosing larger problems. (Each time the car NEVER ran hot for long and NEVER ran in the red on the temp gauge).
First the water pump went, then was the oil filter adapter gasket. Each of these repairs resulted in having to burp the system…so I am not new to that.
Well, this leads me to the current issue. 2 weekends ago I was driving the Mach around, went sitting in a little traffic I noticed she’s running a little hot. As soon as traffic clears up and I’m moving again she drops back down to normal range. I get it home and pop the hood and check the expansion tank. Cant see any fluid line at all. So I wait till she cools down a bit and open the cap…its really low.

I’ve not noticed any coolant leaks under the car when I do drive it (not my daily driver any more). So, I get some 50/50 and top things off. The next Monday, I decide to drive it to work. Get a few miles from the house and boom she starts running warm. I swing back to the house to swap out cars, on the way back, temp drops back to normal range and stays there the whole way home.

When I park it, I now notice coolant dripping. I pop the hood to see from where…it’s the expansion tank and the cap.
Ordered new cap, it got here last Thursday and I put it on and followed burping procedures listed here: http://www.reischeperformance.com/refill.html

During the first drive/heat soak she ran fine…temp (now I have my logger plugged in) never went above 216*F, and that was with running her real hard on the highway….lots of mid-RPM shifts.

I let it sit all night, then check at the coolant the next day. Expansion tank is a little low (maybe half filled), so I top it off (WITHOUT removing the crossover plug yet). I cap the expansion tank, then check at the coolant crossover. Its just a little low as well, so it gets topped up and plug back in.
A send drive/heat soak. Similar as the first, a lot of hard and mid-RPM pulls on the highway (at highway speeds of course  ). Let it set again over night, and just got done checking. Coolant in the expansion tank just a little low, and at the crossover shes all topped up…coolant starts dribbling out as soon as I start cracking the plug open.

Two questions:

(1) Is it possible that the issue was just the bad expansion cap? I assume it was the original and the spring seemed to literally be stuck. No movement on it like the new one I replaced it with.

(2) Since my level at the crossover is good…is it okay to open the expansion and top it off there? Or should I never mess with opening the expansion tank at all from this point on?

I still have plans to test drive it and check some other things out; like ruling out a fan issue, or possibly the thermostat. But both of those are relatively new. New fan about 15k miles ago, and new thermostat about 25k miles ago (when I replaced the water pump).
Thanks in advance for any input.

USMCWeatherMan · 03-12-2017, 07:14 AM

Just wanted to post a follow up in case searches landed people here. After a week and several more drives/heat soaks things are still on the up and up. During one of the times I was checking coolant at the crossover, the el-cheapo 1/4" ratchet attachment tip twisted off in the plug...so I ordered a new one from LMR.

Upon replacing it, I also noticed the o-ring on the original plug was gone. Not quite sure how I missed that before. Probably too distracted with worries of it being larger issues.

Anyway, I think I'm gonna call this one solved...and just quick PSA. Our cars are getting old, and sometimes it the small things that will cause issues like a bad/sticking expansion tank cap, or missing/dry-rotted o-ring, etc.

Should anything change, I'll post an update.

sutyak · 03-12-2017, 11:52 AM

These cars are so backwards since coolant needs added to the crossover and not the expansion tank. My experience has been that adding coolant at the expansion tank does nothing to help overheating issues, so I won't even open mine unless I'm prepared to perform the entire burping process again.

USMCWeatherMan · 03-12-2017, 03:45 PM

Yeah, thats what I figured. I had to add about a 1/2 a cup in the expansion tank...but did so without removing the cross-over plug. Coolant at the cross-over plug is good and has been since re-burbing.

Will keep an eye on it since I did crack open the expansion tank to top it off.

02-27-2017, 04:43 PM	#1
USMCWeatherMan Registered User Join Date: Nov 2008 Location: Haymarket, VA Posts: 532	Running Hot / Coolant Woes So twice before I had issues that first presented themselves as overheating leading to diagnosing larger problems. (Each time the car NEVER ran hot for long and NEVER ran in the red on the temp gauge). First the water pump went, then was the oil filter adapter gasket. Each of these repairs resulted in having to burp the system…so I am not new to that. Well, this leads me to the current issue. 2 weekends ago I was driving the Mach around, went sitting in a little traffic I noticed she’s running a little hot. As soon as traffic clears up and I’m moving again she drops back down to normal range. I get it home and pop the hood and check the expansion tank. Cant see any fluid line at all. So I wait till she cools down a bit and open the cap…its really low. I’ve not noticed any coolant leaks under the car when I do drive it (not my daily driver any more). So, I get some 50/50 and top things off. The next Monday, I decide to drive it to work. Get a few miles from the house and boom she starts running warm. I swing back to the house to swap out cars, on the way back, temp drops back to normal range and stays there the whole way home. When I park it, I now notice coolant dripping. I pop the hood to see from where…it’s the expansion tank and the cap. Ordered new cap, it got here last Thursday and I put it on and followed burping procedures listed here: http://www.reischeperformance.com/refill.html During the first drive/heat soak she ran fine…temp (now I have my logger plugged in) never went above 216*F, and that was with running her real hard on the highway….lots of mid-RPM shifts. I let it sit all night, then check at the coolant the next day. Expansion tank is a little low (maybe half filled), so I top it off (WITHOUT removing the crossover plug yet). I cap the expansion tank, then check at the coolant crossover. Its just a little low as well, so it gets topped up and plug back in. A send drive/heat soak. Similar as the first, a lot of hard and mid-RPM pulls on the highway (at highway speeds of course  ). Let it set again over night, and just got done checking. Coolant in the expansion tank just a little low, and at the crossover shes all topped up…coolant starts dribbling out as soon as I start cracking the plug open. Two questions: (1) Is it possible that the issue was just the bad expansion cap? I assume it was the original and the spring seemed to literally be stuck. No movement on it like the new one I replaced it with. (2) Since my level at the crossover is good…is it okay to open the expansion and top it off there? Or should I never mess with opening the expansion tank at all from this point on? I still have plans to test drive it and check some other things out; like ruling out a fan issue, or possibly the thermostat. But both of those are relatively new. New fan about 15k miles ago, and new thermostat about 25k miles ago (when I replaced the water pump). Thanks in advance for any input.

03-12-2017, 07:14 AM	#2
USMCWeatherMan Registered User Join Date: Nov 2008 Location: Haymarket, VA Posts: 532	Re: Running Hot / Coolant Woes Just wanted to post a follow up in case searches landed people here. After a week and several more drives/heat soaks things are still on the up and up. During one of the times I was checking coolant at the crossover, the el-cheapo 1/4" ratchet attachment tip twisted off in the plug...so I ordered a new one from LMR. Upon replacing it, I also noticed the o-ring on the original plug was gone. Not quite sure how I missed that before. Probably too distracted with worries of it being larger issues. Anyway, I think I'm gonna call this one solved...and just quick PSA. Our cars are getting old, and sometimes it the small things that will cause issues like a bad/sticking expansion tank cap, or missing/dry-rotted o-ring, etc. Should anything change, I'll post an update.

03-12-2017, 11:52 AM	#3
sutyak it's soo-tack Join Date: Nov 2002 Location: Fairmont, WV Posts: 2,082	Re: Running Hot / Coolant Woes These cars are so backwards since coolant needs added to the crossover and not the expansion tank. My experience has been that adding coolant at the expansion tank does nothing to help overheating issues, so I won't even open mine unless I'm prepared to perform the entire burping process again. __________________ mark 2004 DSG Mach 1. Built motor. Turbo. 667whp 2006 Sonic Blue Focus. Built motor. Turbo. 12.4 @ 115mph (sold) 2003 DSG Mach 1. 12.65 @ 106 (sold)

03-12-2017, 03:45 PM	#4
USMCWeatherMan Registered User Join Date: Nov 2008 Location: Haymarket, VA Posts: 532	Re: Running Hot / Coolant Woes Yeah, thats what I figured. I had to add about a 1/2 a cup in the expansion tank...but did so without removing the cross-over plug. Coolant at the cross-over plug is good and has been since re-burbing. Will keep an eye on it since I did crack open the expansion tank to top it off.

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