stock 69 overheating
Thread Starter
Racer
Joined: Jan 2004
Posts: 463
Likes: 0
From: South Haven MI
stock 69 overheating
My stock 69 overheats after about 20 minutes of stationary idling. It doesn't overheat while driving. Have a new thermostat. I just got the car a couple weeks ago and am just now getting to stretch its legs and finding stuff. The radiator looks brand new. No bent fins, no dirt in the fins, everything looks brand new. The coolant is flowing through the tubes and it looks really good inside the radiator. The water pump is not leaking at the weep hole but I'm wondering if its pumping enough water. Can water pumps lose their pumping volume? The car has an original 45K miles on it and I'm sure it is the original pump. Any help and stories of shared expieriences would be appreciated :) CF is great!
Racer
Joined: Dec 2003
Posts: 275
Likes: 6
From: NY
Re: stock 69 overheating (jacobsed)
My '71 454 has the same issues. I R&R'd the water pump, not it. Water pump impeller is stainless steel. The cores were plugged. Car sat for 12 yrs. I removed both water hoses to the rad and saw water still water sitting in the return hose with the exit removed. Rad shop said the core had many channels plugged. Installed but not tested, yet.
Safety Car
Joined: Sep 1999
Posts: 4,930
Likes: 11
From: AnyTown NJ
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Re: stock 69 overheating (jacobsed)
Do a pressure test. One of the simple things most overlooked is the rad cap. Even if it's new it may not be holding the desired pressure. :chevy
Instructor
Joined: Nov 2002
Posts: 157
Likes: 0
From: Greenbush WI
Re: stock 69 overheating (jacobsed)
The answer is in your question!
The car in motion is fine, at a stand still it overheats. There's no air movement! I will bet that replacing the viscous clutch on you fan will fix your problem and while your at it check all the belts. Also be sure your idle speed is set to the correct RPM. If set too low, again, not enough air movement.
The car in motion is fine, at a stand still it overheats. There's no air movement! I will bet that replacing the viscous clutch on you fan will fix your problem and while your at it check all the belts. Also be sure your idle speed is set to the correct RPM. If set too low, again, not enough air movement.
Team Owner
Joined: Jul 2001
Posts: 182,997
Likes: 88
From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
Re: stock 69 overheating (geezer)
The answer is in your question!
The car in motion is fine, at a stand still it overheats. There's no air movement! I will bet that replacing the viscous clutch on you fan will fix your problem and while your at it check all the belts. Also be sure your idle speed is set to the correct RPM. If set too low, again, not enough air movement.
The car in motion is fine, at a stand still it overheats. There's no air movement! I will bet that replacing the viscous clutch on you fan will fix your problem and while your at it check all the belts. Also be sure your idle speed is set to the correct RPM. If set too low, again, not enough air movement.
Clutch fan is the most likely reason...
Le Mans Master
Joined: May 2000
Posts: 6,493
Likes: 6
From: Bloomington MN
Cruise-In II Veteran
Re: stock 69 overheating (GrandSportC3)
Not to mention the fan shroud and seals. From your description, it's lack of airflow at idle, not lack of coolant flow (which wouldn't change regardless of speed).
Thread Starter
Racer
Joined: Jan 2004
Posts: 463
Likes: 0
From: South Haven MI
Re: stock 69 overheating (gq82)
How do I do a rad cap test? And if it is bad how does that make the car overheat while it it idling? currently, I'm running Prestone cleaner/flush through the system. My gut is telling me the radiator is old and plugged in cartain areas and I'll probably just need to get it recored. It looks perfect though.
Thread Starter
Racer
Joined: Jan 2004
Posts: 463
Likes: 0
From: South Haven MI
Re: stock 69 overheating (geezer)
There is no clutch that I can identify. It appears to be a straight drive to the fan. Is this typical for 69? My 79 has a cylindrical clutch to the fan but there doesn't appear to be a clutch on the 69.
[Modified by jacobsed, 6:21 PM 2/29/2004]
[Modified by jacobsed, 6:21 PM 2/29/2004]
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Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Re: stock 69 overheating (jacobsed)
Do a search on "engine pics" and "cooling". See if what you see is like yours. I am not aware of a vette that is stock not having a radiator shroud. With the angle of the radiator and the openings etc. it needs the air to be pulled into the radiator. Good luck, do your research.
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
Re: stock 69 overheating (jacobsed)
Sounds like an aftermarket fixed fan, many of which are awful on vettes, especially the flex fans. Also, the stock '69 shroud completely seals the radiator so all the air has to be pulled in by the fan. If your shroud doesn't cover the entire radiator (including foam seals at the top and sides), it won't work at idle due to the radiator angle. Post a picture if you can. It would be a big help.
Because it works (getting air flow) while the car is moving, you can forget about the radiator, thermostat, cap, etc. till you get some air moving through that radiator.
Hans
Hans
Because it works (getting air flow) while the car is moving, you can forget about the radiator, thermostat, cap, etc. till you get some air moving through that radiator.
Hans
Hans
Thread Starter
Racer
Joined: Jan 2004
Posts: 463
Likes: 0
From: South Haven MI
Re: stock 69 overheating (Wrencher)
Thanks for all the suggestions guys. I'll post a pic late tomorrow. The shroud is all stock. I think it is a case of age and some of the core is plugged. When I had my 79's rad recored it only cost me 80$.
Team Owner
Joined: Aug 1999
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SPARTAN
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Re: stock 69 overheating (jacobsed)
Yup. Sounds airflow related for sure.
Your fan should sit about half INSIDE the shroud with just a little clearance between it and the shroud around the outside. It should look like a normal "GM fan" with 5 or 7 blades and a clutch.
Your fan should sit about half INSIDE the shroud with just a little clearance between it and the shroud around the outside. It should look like a normal "GM fan" with 5 or 7 blades and a clutch.
Advanced
Joined: Jan 2001
Posts: 83
Likes: 0
From: Snellville, GA, USA
Re: stock 69 overheating (jacobsed)
I have a 69 with a ZZ4 crate motor. It has a fan clutch and a fan shroud. It is different from what is pictured above though. Mine is more of a plastic. No metal. There are several pieces of foam that go between the radiator and the radiator support. It is very important that these are in place because as you are finding out all moving air needs to pass through the radiator. If you pics of what my shroud looks like email me and I will be glad to post some.
good luck
steve
good luck
steve
Melting Slicks
Joined: Mar 1999
Posts: 2,845
Likes: 2
From: Apex NC
Re: stock 69 overheating (jacobsed)
There is nothing sealing the shroud against the radiator core. You should have a plastic shroud that extends fully to the side tanks on the radiator. Between the shroud and radiator there should be foam seals that will fil all the space between the two.
It appears that you have a shroud from a base model radiator (18" core" but you're running a 26" core radiator. The entire system should be configured properly to get acceptable cooling. I have the same radiator in my '69 L-46 car, but with the correct shroud and thermal clutch fan. It will idle all day long at 180*. Set it up properly and you should be good to go.
Shannon
It appears that you have a shroud from a base model radiator (18" core" but you're running a 26" core radiator. The entire system should be configured properly to get acceptable cooling. I have the same radiator in my '69 L-46 car, but with the correct shroud and thermal clutch fan. It will idle all day long at 180*. Set it up properly and you should be good to go.
Shannon
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SPARTAN
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Re: stock 69 overheating (jacobsed)
Yikes!!!! :eek:
1) Remove that fan immediately
2) Install a proper fan with a clutch
3) Problem solved
That fan is your entire problem. It sucks. Bubba put one a lot like that on my car (except red :rolleyes: ) and my car would do the same thing with the overheating at idle. That fan does NOT move enough air to be effective at all!
1) Remove that fan immediately
2) Install a proper fan with a clutch
3) Problem solved
That fan is your entire problem. It sucks. Bubba put one a lot like that on my car (except red :rolleyes: ) and my car would do the same thing with the overheating at idle. That fan does NOT move enough air to be effective at all!