Thermostat problem
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
Thanks noonie. I was wondering where to drill the holes. How you explain it is exactly what I was thinking was happening. You just explained it very well. As I said above the LT1 recovery system is non existant. The rad if I fill it up to the top cold will expell about a pint of fluid at operating temps. It has always since I owned it after cool down the level is about 2 inches below full. I'll just drill the holes as you picture and fill it carefully. Thanks again.
Thread Starter
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Instructor
Joined: Aug 2008
Posts: 159
Likes: 0
From: Northern California
Any update on this? I'm having this exact same issue after changing my radiator fluid this weekend and installing a heater-core feed line shut-off valve. Mine drives fine 75% of the time, then suddenly spikes to 210-220 degrees and then goes back down quickly. Before I changed the fluid and added the shut-off it ran around 185-195 even during rough driving. With the valve open, which essentially negates the shut-off fix I implemented, it still does the same thing. Feels like there is air in the line. The hose coming from my radiator to my block feels a bit soft like there's no water running through it.
Instructor
Joined: Aug 2008
Posts: 159
Likes: 0
From: Northern California
I did. I measured exactly what came out as well to be sure I'd put that much (or more) back in. It's an aluminum radiator if that makes any difference. From what I can tell, it feels like there's either a minor leak keeping the pressure from building up and circulating the fluid, there's air in the line that's allowing it to heat up and then dump fluid in and cool it off rapidly, or the thermostat is bad and opening too slowly so that it only cools the engine after 200-210 degrees. Here's the 3 things I'm going to look at tonight.
1. Radiator Cap: Removed it for the first time in a long time yesterday, and it was old, maybe even original. Thinking maybe it's not creating a tight seal anymore??
2. Drill current thermostat after testing to ensure it's functional. If I find it still works, I'm going to drill the hole in that first to see if it will bleed the line free of air and eliminate the spikes in temp.
3. thermostat: Buy new thermostat. If that alone doesn't work, I'll vent it with a drill hole to bleed the air from the line.
Mine runs around 180-195 degrees and then suddenly spikes to 210-220, then immediately drops back down. The spikes are freaking me out, though. It hasn't run that hot since I first drove it home the day I bought it (last August). It was 75 degrees this morning and the car spiked to around 210, which is way above normal for my car. Any time it hits 200 I get nervous. When it spiked, I was in the middle of an expressway... not idling or sitting for a prolonged period. It just jumped up as I was driving around 40mph and then dipped back down and stayed at 185 degrees. I got it to work and my buddy came to take a look, and the line that dumps from the radiator into the block was soft, as if there were no water or pressure. We started it up and it idled at 185 degrees in the parking lot for 15 minutes with no issues.
Car info: Small block GM 350 Crate motor, 1968 convertible, no A/C, manual transmission, headers, just installed the heater-core shutoff hose to get rid of cabin heart. The issue occurs with the valve open or closed to the heater core, so I don't think that's the cause.
1. Radiator Cap: Removed it for the first time in a long time yesterday, and it was old, maybe even original. Thinking maybe it's not creating a tight seal anymore??
2. Drill current thermostat after testing to ensure it's functional. If I find it still works, I'm going to drill the hole in that first to see if it will bleed the line free of air and eliminate the spikes in temp.
3. thermostat: Buy new thermostat. If that alone doesn't work, I'll vent it with a drill hole to bleed the air from the line.
Mine runs around 180-195 degrees and then suddenly spikes to 210-220, then immediately drops back down. The spikes are freaking me out, though. It hasn't run that hot since I first drove it home the day I bought it (last August). It was 75 degrees this morning and the car spiked to around 210, which is way above normal for my car. Any time it hits 200 I get nervous. When it spiked, I was in the middle of an expressway... not idling or sitting for a prolonged period. It just jumped up as I was driving around 40mph and then dipped back down and stayed at 185 degrees. I got it to work and my buddy came to take a look, and the line that dumps from the radiator into the block was soft, as if there were no water or pressure. We started it up and it idled at 185 degrees in the parking lot for 15 minutes with no issues.
Car info: Small block GM 350 Crate motor, 1968 convertible, no A/C, manual transmission, headers, just installed the heater-core shutoff hose to get rid of cabin heart. The issue occurs with the valve open or closed to the heater core, so I don't think that's the cause.
Last edited by fe1ixdakatt; Jun 29, 2009 at 04:47 PM. Reason: added car info
Burning Brakes
Joined: Jan 2006
Posts: 1,088
Likes: 181
From: NC
2022 C2 of the Year Finalist - Modified
ANOTHER WAY TO HELP ELIMINATE THE AIR BUBBLE AT THE THERMOSTAT PROBLEM IS TO REMOVE THE THERMOSTAT HOUSING WHEN FILLING A DRY ENGINE AND FILL IT THRU THE THERMOSTAT HOLE.
WHEN IT'S FULL, REINSTALL THE THEMOSTAT AND TOP OFF AT THE RADIATOR IF NEEDED.
THIS IS DONE IN ADDITION TO THE DRILLED THERMOSTAT.
WORKS EVERY TIME FOR ME.
BILL SR
WHEN IT'S FULL, REINSTALL THE THEMOSTAT AND TOP OFF AT THE RADIATOR IF NEEDED.
THIS IS DONE IN ADDITION TO THE DRILLED THERMOSTAT.
WORKS EVERY TIME FOR ME.
BILL SR
Burning Brakes
Joined: Jan 2004
Posts: 769
Likes: 0
From: Ft. Lauderdale Fl
change thermostats. a 195 should start to open at about 175 and be fully open at 195 . if it starts to open at 190ish its not working correctly. i dont think its all of your problem but it will help. did u drill a 1/8 hole in the side plate of the t/stat to allow an airpocket pass cause it sound like an airloc problem. bottom rad hose still have the spring in it? on a good note glad your F.I is great !! wish i had it.
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Verdad Gallardo
Instructor
Joined: Aug 2008
Posts: 159
Likes: 0
From: Northern California
I just bought another thermostat that came with a little hole pre-drilled to bleed the air. It has this little steel grommet in it that allows just enough air to pass through the thermostat to bleed the line. I also found out my thermostat was a 160, so I bought another 160 with the bleed hole, installed it, and she's running at a cool 185 degrees now. The real test will be a trip to work tomorrow morning. However, I ran it hard for a good 20 minutes and it never once spiked higher than 195 even though it's in the low 90's today. Yesterday when I was driving I could see it go up to 210+ about once every 5 minutes or so.
The real test will be a trip to work tomorrow morning. However, I ran it hard for a good 20 minutes and it never once spiked higher than 195 even though it's in the low 90's today. Yesterday when I was driving I could see it go up to 210+ about once every 5 minutes or so.
