Pontiac GTO Forum banner

101 - 116 of 116 Posts

·
Registered
Joined
·
8 Posts
Let me preface this with a disclaimer: I am NOT a mechanic, in any way, shape or form. And I didn't stay at a Holiday Inn Express last night either...so I thought I'd come to the best source of Pontiac info on the internet in search of a solution....

I just took delivery of my "new" '69 GTO Tribute convertible, which supposedly has less than 500 miles on the rebuilt engine, transmission and rear end. I live in San Antonio, and temps here are currently hovering around 100*...On my first little jaunt, I noticed three things:

a) At highway speeds (65+) the engine seemed to be working REALLY hard, which I attributed to the 3-speed turbo 400 transmission and the gear ratio that has it in 3rd gear by 40 mph, so any additional speed is all RPM's...
b) When initially started, the temp gauge sat right at the mid point of the gauge...after running for a while (just a few minutes) at highway speeds the temp gauge started creeping up to the 3/4 mark, so I slowed down to about 55 and it began cooling back towards the midpoint.
c) The oil pressure, which starts out great, dropped down to the lower 1/4 of the gauge when the engine was running hot, and stayed there even when the temp started coming back down...

After reading this thread, I've gotten LOTS of useful info to share with my mechanic about potential solutions to the overheating problem, but I have two questions...

a) Could the oil pressure problem be related to the running hot?
b) How difficult is it to change the gear ratio to not have the engine working so hard at highway speeds? I don't want to have to drive the car at 50 mph its whole life...seems sacreligious! :mad2::mad2:

Thanks in advance for any additional info. This thread (and this forum) are GREAT sources of info!!
 

·
Super Moderator
Joined
·
5,741 Posts
:agree: Also search on this forum for threads relating to Pontiac engines overheating and how to keep them cool. There have been lots of conversations here on that topic.

and.. Welcome!

Bear
 

·
Registered
Joined
·
9 Posts
389 overheat problem

Hi Richard here new to forum. I'am a 65 GTO owner for 24 years and all this time I have had heating issues none so bad I could not drive it but just never felt it was right. This year things started going south so I tore into water pump found plates and timing chain cover gone on the inside. I thought I had my cooling issue whipped, replaced thermostat, new timing chain and gears, timing chain cover, flo cooler water pump with stainless steel plates 11 bolt, radiator cleaned and boiled out. I was going to a show tonight everything started out fine below 180 with 160 degree thermo got on interstate and in 30 miles temp just stated creeping up to above 220. It was so hot it was moaning spitting steam blew antifreeze out, sat 3 hours I started it right up added water made thermo opened loaded on trailer and brought it home. I have no idea what to try or do next, need help!!!!!
 

·
Registered
Joined
·
346 Posts
Hi Richard here new to forum. I'am a 65 GTO owner for 24 years and all this time I have had heating issues none so bad I could not drive it but just never felt it was right. This year things started going south so I tore into water pump found plates and timing chain cover gone on the inside. I thought I had my cooling issue whipped, replaced thermostat, new timing chain and gears, timing chain cover, flo cooler water pump with stainless steel plates 11 bolt, radiator cleaned and boiled out. I was going to a show tonight everything started out fine below 180 with 160 degree thermo got on interstate and in 30 miles temp just stated creeping up to above 220. It was so hot it was moaning spitting steam blew antifreeze out, sat 3 hours I started it right up added water made thermo opened loaded on trailer and brought it home. I have no idea what to try or do next, need help!!!!!
you can read back in this forum about proper spacing of the plates in relationship to the "vanes" on the water pump. Once you read about it, then the question is did you do the adjustment.
 

·
Registered
Joined
·
49 Posts
LOTS of information here guys.
To be honest my head was spinning after the first 6 pages.

I never saw MY thoughts mentioned so - even though they may be in the last 5 pages - I'll throw them out there.

As a mechanical engineer graduate that majored in thermodynamics, and a 68 GTO owner for 20 years, I've learned a few things (often the hard way) that have helped me with mine.

The fins/tubes of the radiator must be clean clean clean.
There is an acidic type cleaner commonly used on house A/C that can be used on cars as well. SHINY FINS and tubes go a long long ways.
Used the fin brushes - plastic Harbor Freight $1 - to make sure fins are straight.
The air needs to pass as easily as possible through the fins.

Even SOAP FILM on fins/tubes will decreae the heat transfer.
Clean water rinse.

An A/C "radiator" sitting next to the real radiator WILL slow air passage.
Sad but true.
Remove the A/C the ENGING will run cooler.
Tough call on that.
I live in Memphis.

Use rubber/tin or similar sheets to deflect all possible air from the front of the car into/through the radiator.
In summer, the air is hotter closer to the street (even though heat rises) so try to grab air from up high and deflect it DOWN to the radiator.

Some owners have gone as far as painting their radiator FINS black because it looks cleaner from the front - needless to say this is beyond bad.
Remove/replace it.

Car won't start after shutting it off at the gas station?
Header wrap - insulation woven into a cloth roll is the bomb.
Worth ALL the headaches of removing the headers to wrap/bind them up tight.
Near impossible to do it ON the car but it can be done.
I had that problem and it kept frying solenoids.
Now I can LITERALLY grab the headers while RUNNING the engine and they are warm but will not burn. Cools the engine compartment down dramatically and no doubt everything associated with it. Even the temp of the air going into the carb.

They make a similar product for the starter (a shiny insulating blanket) and of course the factory stock or aftermarket solenoid shields help also.

Lastly - after chasing down my everheating 400 one summer and replacing nearly everything but the radiator CAP - I replaced the radiator CAP.
It WORKED!!.
The thermostat inside the cap had gone bad or just dirtied up but the result was the same.
Water will boil and steam at 212 when NOT under pressure and blow out under the hood even though the car is not necessarily overheating.
Upwards of 250+ when pressurized.
If you are constantly smelling coolant and finding moisture under the hood with no visible signs of leaks, replace that cap.

One more - I actually had a friend that thought PURE antifreeze would cool an engine better than 50/50 water mix.
Do NOT make that mistake.
You need 50 percent water to cool an engine properly.
Way better than pure antifreeze.
 

·
Premium Member
Joined
·
27 Posts
Greetings everyone. Ive been following the various threads on running hot over the last 14 months with great interest and hope that my experience may help those having similar problems. I have a 65 Tempest sports coupe 326 bored .030 over with a mild melling cam that was running at 200 cruising and climb to 220 stuck in traffic regardless of the air temp.The timing and all other obvious potentials have been checked and the engine was running like that since the rebuild and correct cam break in procedure. Ive been making adjustments over the last year one at a time to see what would ultimately drop the temp to a more comforting level. It now has the 65 Tempest chassis manual recommended 180 thermostat. My research from the chassis manual states that the temp light comes on at 248.I finally found the normal operating temp in the 65 Tempest reliability assurance inspectors guide page 41 under the hot idle speed adjustment and it says adjust at normal operating temp 177 to 182. This manual covers all Tempest,Lemans and GTO motors. One more interesting note is found in the 65 owners guide and says normal operating temp should be 180 or above . If gauge reads 245 take immediate action to find the cause. The following are the items I changed or added with little or no effect 1) high flow 180 thermostat 2) high flow water pump/ flow cooler. 3) divider plate adjusted from 1/4 inch to 1/16. 4) a four core brass copper desert radiator. 5) added a fan shroud. 6) changed from a four blade to a clutched 7 blade.8) a dual electric fan set up pushing with a thermostat set to come on at 200. This kept it from going over 212 stuck in traffic and did help with the peak temp lowering it 8 degrees 9) out of desperation added water wetter. And finally what worked ?? I installed a U.S. radiator aluminum desert cooler radiator that appears stock. Now she runs down the road at 180 and never went over 200 stuck in traffic with outside temp at 95 (HALLELUJAH).I tried to keep it simple but wanted to share my experience and highly suggest after first checking the common culprits as already discussed in previous threads that trying an aluminum radiator first may save a lot of time and money. Ive posted a few slide shows of my restoration on You Tube titled 65 Tempest Restoration for those interested.
Happy motoring to you all
 

·
Premium Member
Joined
·
84 Posts
zink plates on ebay (two GTO,s both w/ heat problems)

I bought set of these zinc plates on eBay --they are exact copies of the OEM plates and the fit is perfect on the original pump in my 68--no clearance modifications needed ---I Have flex fan (Non A/C car) 180 degree thermostat--runs at 180 on the highway--but can get to 195 in heavy traffic on the same approx 90 degree day.
I also have a 64-389 tri power (65 engine)--it has a flow cooler water pump--the owner at flow cooler said two different things in two different calls about the clearance of the plates -- one time he said if the plates are too close to the shroud covering the fins on the pump that the water can't get in the way it is supposed to--the next call when I mentioned what the guys on the forum said; he said to decrease the clearance to the plates as we are told. So what do i believe now?
I had a radiator specialty mfg re core 64 rad --they increased the cooling from 84 inches to 142 inches--they said it would make a huge difference--but it didn't? He then told me that because the inlet on the top of the rad is straight above the lower outlet tube (same side of the rad) that that cuts the efficiency drastically; because most of the water runs down the one side--He has offered to add a cooling tube to the bottom so the water outlets on the opposite side (passenger) and says he will do it for (no charge) and he thinks this may be a major problem with hot Pontiac's.--(a lot of guys have tightened the clearance of the divider plates and they still run hot)
Has anyone tried this?--a good mechanic friend thinks this will help a lot!
I'll post back.:banghead:
 

·
Super Moderator
Joined
·
5,741 Posts
Wellsir, I can tell you from my own personal experience that "plan B" (tightening up the clearance on the divider plate) made a HUGE difference on my car. I'm running an aftermarket aluminum "high flow" pump (don't recall which manufacturer right now).

The thing is, this mod is very easy to do, or undo. Pick a direction and try it. If you don't like the results, then try "the other one". :D

Bear
 

·
Registered
Joined
·
773 Posts
Guys, putting a TH350 in my 66 Lemans, need to rout. The new coolant lines, does anyone recall if original trans coolant lines go above or below the sway bar? It looks awful close either way, want to get it right and not bend the new lines. Ripped off the old ones, buts. I can't recall above or below.....it always happens!
 

·
Registered
Joined
·
93 Posts
Great read. I have this same issue with my 1966 Tempest with the stock rad and 326 engine. Replaced upper rad hose, t-stat, and rad cap. So far so good. Car hasn't spit coolant since I did this. However, I did buy a new water pump, shroud, and clutch fan, for install this winter.

I read earlier that one of the posters said to make sure that the lower rad hose has a spring in it. I checked and the current one does, but the new one I bought does not. What is this springs purpose and can I just take the old one out and put it in the new one? Thanks for any help.
 

·
Registered
Joined
·
8 Posts
Another thing I have found to be miss-understood is vacuum advance. Additional advance coming from the vacuum advance at idle helps keep your car cool and provides better throttle response.

If someone along the line has removed it put it back

Also if you have replaced your carb with a holley or other aftermarket carb and the vacuum advance is hooked to the ported vacuum ( as it actually states in some of the installation manuals) change it to a manifold vacuum port. Ported vacuum is an emission control. It removes vacuum advance at idle to raise operating temp and burn the gases more completely.

You want this advance from a performance perspective and to keep your old beast cool
 
101 - 116 of 116 Posts
Top