My freshly rebuilt engine has been overheating since I put it in. I just replaced the 6 blade 17 inch static fan with a 19.5 inch 7 blade clutch fan with a new fan clutch, but the car still heats up very quickly. When I took the car out for a test drive, the engine rose to 240 degrees in about 15 mins while driving around the city. It rose faster while idling. When I shut the car off the temp quickly raises to 250 or above (my tenp gauge only goes to 250). It acted similar with the 17 inch fan.
After shutting the car off, I could hear the fluids making a gurgling sound in the engine.
Here is some more background: 1) This is a 68 firebird that came originally with a 350 auto trans and A/C. The A/C was gone before I got it and now it has 73 455 that is newly rebuilt. I changed the trans from an auto to a 4 speed. 2) The water pump is new 3) The radiator is the original 3 core automatic trans unit that worked fine with the previous 350 engine. I changed the trans to a 4 speed and plugged the trans line holes in the radiator. 4) The timing cover is from the 68 350. 5) The backing plate is somewhat pitted, but has no holes 6) The top baffles are in 7) I have a shroud. 8) I changed the fan from a 6 blade 17 inch to a 7 blade 19.5 inch. The fan fits about 1/4 way into the shroud. 9) I added water wetter and have a 50/50 mix of radiator fluid and water. 10) The heater core is new. 11) The water line is 3 inches from the top 12) The radiator did not spill out when the temp rose too high or when I shut the car off.
Now that I have the proper fan in, any thoughts on where I should take this troubleshooting next?
Your thermastat may be sticking or was installed upside down. Pull it out and run the motor without it and see what temp. it runs at. Put the thermastat in a pot of water heat it on a stove. Put a cooking thermometer in and see what temp it opens up at.Make sure you don't have the heater hoses on bakwards. That is where I would start and go from there.
It may be hard to tell with a new engine, but an engine running above ideal temps starts to sound ragged. If it's really hot, you will here "ting" sounds from the exhaust manifolds, brackets, and other pieces as they cool. I suspect that your sending unit and gauge may not be well calibrated, but just to be safe...
1. What type of sending unit are you using...one piece gauge with thermocouple, or electric sending unit? If electric, is the sending unit designed to match the gauge? If not, your gauge reading will not be accurate.
2. Ditto on the thermostat. It's easily overlooked. I usually drill an 1/8" hole or three in the thermostat plate as well to aid in the removal of trapped air.
3. Does the water pump have cast or stamped impellers? Did you check the clearance between the vanes and the backing plate?
4. Depending on the age of your radiator, it may be partially clogged. The water passages build up mineral scale and close off circulation. What may have been enough cooling capacity for a 350 may not be enough for a brand new 455. You can remove the coolant and have a radiator shop inspect it. A few hundred dollars for a new radiator will pay itself back many times over.
The water level in the radiator sounds a little low. When fully cool, add coolant to the fill line, about 1 1/2" to 2" below the neck. Set the cap in place and squeeze the upper radiator hose. You should hear liquid sloshing from the tank to the water pump and back. If not, add a little more, but not full. You should be able to see the liquid moving in the radiator when you do this. Then close the cap securely. A very small amount of coolant, one cup or less, may dribble out after the car reaches operating temperature. Leave the radiator sealed once it does.
Vikki 1969 Goldenrod Yellow / black 400 convertible numbers matching
You said you no radiator fluid is spilling out but have you noticed less in the radiator? If so, you might want to check the oil to see if it looks foamy or cappucino like. Probably unlikely, but maybe the head gasket isn't sealed properly on the new rebuild and radiator fluid is in the oil. It's probably something mentioned above but you might want to check that too.
"An ignorant man thinks he knows everything, a wise man knows he doesn't."
Thermostat, I could have put that in wrong, I can't remember, so I'll check that out.
Vikki, here are your answers: 1) Sunpro guage using the thermo sending unit it came with. It seems to be accurate given the rate it increased as the tempeture changed. Also, since I heard the liguids boiling in the engine, I'm assuning the 250 temp was correct. 2) I'll check it out. 3) I can't remeber what the impellers were, but I do remeber looking at the clearnece and thinking it was close. But to be sure I could take another look. 4) Th radiator is the original one and worked well when I pulled it out of the car years ago. It could have restrictions due to age though, so I can have that checked.
Sheri, acutally what I meant was that the fliud level was unchanged. I filled it to 3 inches below the cap and the level didn't seem lower much after it heated up.
I'll get back to the car in a few days, so I'll try the thermostat, check the oil for foam, and squeezing the upper hose, and go from there.
Just so you know, once pics are posted on another site such as photobucket all you do is copy and paste the imgage code directly into your posting on this site and the pic will be added right in your post.
I say this because I don't think most people know how to do this...
1) Since you already have the thermo housing off, just remove the thermostat entirely, then try it again to see what happens. Start the car (engine cold) with the radiator cap off. Look down the neck, is the water circulating? If it is, you know the water pump is working, and the impellar hasn't slipped.
If you already put the thermostat back in, start the car with the engine cold, radiator cap off. There should be no water flow (looking down the radiator neck) until you hit the temp on the thermostat. If you have pressure immediately, then there's a breach from a combustion chamber to a water passage.
2) Does the car idle and run ok BEFORE the engine temp gets to 250? How is it under full throttle? Any pinging or knocking? Your timing could be WAY off, causing the engine to run hot.
3) Is your vacuum advance hooked up? If so, is it hooked up to full or ported vacuum? If you're hooked up to full vacuum, what happens when you pull the vacuum advance hose off (plug the vacuum outlet at the carb)? Does the idle drop? Just making sure your vacuum advance is working.
4) If you don't have one already, get an adjustable timing light, pull the vacuum advance hose off (plug the carb fitting), and rev it to 2500 rpm. You should have around 35 degrees total advance. If you don't, then your mechanical advance weights/springs could have binded, or are not working properly.
5) Finally, if you've already done all the aformentioned timing checks, and everything appears normal, ignore the timing light for now. With the car idling, turn the distributor until you get the highest idle (don't go to the point where you start to hear a miss, that's too far). If you've moved the distributor pretty far from its original setting, then your harmonic balancer ring may have slipped, giving you false timing marks.
The rest of your system sounds fine. Since this is a case where it hits 250 degrees, and isn't just the normal "it runs a little hot" deal we see so often with our Pontiacs, I'm thinking it's more of a timing/distributor issue.
I think the first step though is to make sure you're getting coolant flow through the radiator (test #1 above).
I dropped the thermostat in hot water and it opened up, so it's good.
Thanks Stealthbird. I will try it without the thermostat in this weekend. The car seems to load up and not run very smooth, plus I'm getting black build up at the exhaust tips and subsequently on my garage floor if I run it long enough. I'm sure the carb is out of adjustment and needs to be leaned out. I haven’t got there yet.
Timing - I recently borrowed another harmonic balancer because my last one slipped. I guess it's possible that the one I borrowed is off too. But the car does not ping at all no matter how hard I get on it.
I have a mechanical distributor, so no vacuum to worry about. I haven’t tried an adjustable timing light yet.
As you mentioned, I do want to verify if the cooling system is operating well first. From there I can take a look at the timing again.
Unfortunately, I have to fix a brakes issue before I can take the car for another ride, but once I get that done, I'll be able to spend more time on this issue.
So if you've got plugs in both manifold holes where the temperature gauge sender normally goes, where are you getting your temperature readings from now?
So if you've got plugs in both manifold holes where the temperature gauge sender normally goes, where are you getting your temperature readings from now?
Noticed that also. In the cylinder head? It will read hotter there. Check the timing at idle and at full advance vs rpm. Dont need an adjustable light.
The car seems to load up and not run very smooth, plus I'm getting black build up at the exhaust tips and subsequently on my garage floor if I run it long enough. I'm sure the carb is out of adjustment and needs to be leaned out. I haven’t got there yet.....I have a mechanical distributor, so no vacuum to worry about. I haven’t tried an adjustable timing light yet.
I'm not sure what "mechanical distributor" means, but if it's an aftermarket unit (MSD or Mallory) with no vacuum can, or someone modified your stock distributor to not use a vacuum advance, that could very easily be your overheating problem. A vacuum advance can pull an additional 15-20 degrees of timing at idle or at cruising speed, which will significantly lower your engine temps.
The sending unit is in the head (that's where the old one was when I got the engine). So what is the correct place in the manifold for the sending unit? It certainley makes sense that it would show hotter in the head.
The distributor is a Mallory dual point distributor with mechanical wheights and springs for advancing the timing. No vacume advance is used on these distributors.
Temp unit (Pontiac) should be located in the intake manifold, driver's side. If the gauge is reading 250, yes, it could be the gauge, but sounds like there are some other symptoms. You had mentioned it loads up, etc. Hard to tell whether it's due to overheating, carb adjustments, or your timing. You also mentioned earlier you hear lots of heat ticks when you shut the car off, yet you don't get anything from the overflow hose. If you can see you're getting water circulation, and you don't spew anything out of overflow, it could be the gauge.
A mechanical advance, dual point distributor doesn't serve any purpose on a stock Pontiac 455. Dual point distributors are antiquated technology, and mechanical advance distributors are rarely ever used on street cars. Vacuum advances do wonders for economy, idling, and engine temps, and running a vac advance does not impact performance at all. Do you have a stock GM distributor that you can swap in place of the Mallory unit?
Your right about the distributor. It's from the old days. I used it since it came with the car and I thought if the cam I put in was going to produce a choppy idle, then I should use a non vacuum distributor to keep the vacuum for the power brakes. I heard that a choppy idle can produce low amounts of vacuum. I did install a pertronix pick up to get away from the points.
No I don’t have a stock distributor around to swap it out, but it's certainly something I should think about doing. The cam is a little rough, but isn't that bad at idle.
I kept the thermostat out and moved the temp sending unit to the manifold position and the temp did drop about 10 degrees. Now when the temp got to 230, I shut the car off and it rose to only 240 degrees :-).
I watched the water in the radiator. it circulates nicely, so the water pump seems to be doing it's job.
I'm going to look at the timing now. Since the balancer is borrowed and I can't be assured that is hasn't slipped, then I can't really be 100 % sure that using a timing light will be affective.
So I was thinking of using the "just below pinging" theory, which is if the timing is set just below the point where the engine pings under load, then the timing should not affect the temperature of the engine.
Okay, just advanced the timing to the point where the car would'nt turn over, then backed it out until it would turn over. If the balancer is right, then I went from 12 degrees to about 18 or 20 degrees of advance. The car ran much better than before. I let the car idle. 20 minutes later or so the temp hit 220 and I shut it off.
I heard the fluids boiling in the heater hoses and the thermostat housing and the radiator cap was making a noise.
I checked the oil and there no foaming or anything unusual.
Did you find out if you have low compression pistons like 8point said? If your not sure, did you ask your engine builder?
Maybe the balancer is off. Stealthbird mentioned timing should be around 34 degrees advanced.
Have you used a coolant tester? Suction the radiator fluid when cool and see what it says. I'm not sure if Water Wetter will effect this measurement. With Water Wetter, more water than antifreeze might be helpful. Make sure your using the appropriate amount of Water Wetter for the number of quarts of fluid. This article may help: http://www.racerpartswholesale.com/downloads/WaterWetter.pdf Water Wetter may help the overheating but I think there is an underlying cause that needs to be addressed.
Maybe a new radiator cap might help. The cap should be 14-17 psi on a 400/428. I don't think the 455 would be much different but I may be wrong.
What was the weather temp the day you tested? If it was hot, it's easy for cars to overheat during idle. Like Vikki said, airflow is needed.
"An ignorant man thinks he knows everything, a wise man knows he doesn't."
Sheri, No I don't know what pistons are in it except that their Pontiac. My builder left town with no way to contact him. This is a 73 455, so he could have put in the lower compression pistons that came with the 73s. I believe he said the compression would be 9 to 1, but I can't remember.
For the balancer, yes it could be off, but if I advanced the timing to the point where the car wouldn’t start and then back it up slowly until it would start, then I'm assuming I'm close to the most advanced timing I should have. Yes? If I advance it anymore, it won't turn over well.
I haven’t tried a coolant tester, will do. My cap is old too, so I'll replace that.
The temp was about 70 degrees, the car was sitting in the garage with the garage doors open.
I checked out that post. There's miles of info on the affects of the radiator hose being higher than the radiator cap. I believe my hose is higher than the cap. I'll check when I get home (at work now).
If the pistons are too far down the hole, the heat can't escape as quickly. What heads are you using? If the heads are the smaller chamber size, it may be creating too much compression for those pistons also.
As Vikki mentioned before, a 455 is harder to cool than a 350. More heat is being generated but the same cooling system in the block and radiator is being used. It's even more important to have things running as efficiently as possible. The less efficient your system is, the more heat it will generate. If the timing is off a little, it will make a difference. The "ping" theory probably brought you closer but I doubt it is at it's most efficient point. You could probably get away with the "ping" theory on a 350 and maybe 400. I would get a timing light to be as accurate as possible. I think the distributor you are using and the lack of vacuum advance is part of the problem too. That vacuum advance will help with cooling when every little bit of cooling is needed on the 455.
It is important to have your harmonic balancer working right at least to prevent damage to your engine. Harmonic Balancer
Check the top post on cast impellers for a good cooling tip and Running Hot on the HiWay about timing, etc. You could also search some of the other posts.
PY is a great resource for info. FGF is just a percentage of Pontiac owners and PY has many Pontiac owners with valuable knowledge. I figure it's better to give you a link than to repost everything ...lol. I hope this helps.
"An ignorant man thinks he knows everything, a wise man knows he doesn't."
Check the top post on cast impellers for a good cooling tip and Running Hot on the HiWay about timing, etc. You could also search some of the other posts.
PY is a great resource for info. FGF is just a percentage of Pontiac owners and PY has many Pontiac owners with valuable knowledge. I figure it's better to give you a link than to repost everything ...lol. I hope this helps.
and many of us are on both sites! LOL
PY is great for Pontiac general stuff...engines, etc... but FGF is 67-69 Firebird specific ,and if its a 67-69 Firebird question , mostly better answered here...for "general" pontiac issues, PY is a great resource
Yep, a lot of us are on both this site and the PY site!
On the timing issue, don't turn the distributor until the car won't crank, that's not the right way to "set it by ear". The right way is with the engine idling and warmed up, turn (advance) the distributor until you get the highest idle. When you hear the engine start to miss, you went a little too far, back it off a bit. You want the highest idle without the engine missing.
This does NOT address overall timing, curve, weights, springs, etc, but it should get you close to best timing at idle. Try that and see if you temp comes down further. Don't worry if you've advanced it so far that the car won't start, just see what happens to your temps at idle.
If your temp comes down, then you need to get a vacuum advance distributor. The vacuum advance will allow you to have low timing (8-12 degrees at idle), and the vacuum advance will advance the timing to 20-30 degrees at idle to keep the engine running cool.
Okay, I'm getting back to this. Those 12 hour work days are killing my firebird time.
I replaced the radiator cap and checked the fluid. The boiling point on the fluid is 224 degrees.
I advanced the timing as you described, and the temperature rose to 220 degrees after about 20 mins of idling, at which point I shut it off. I think that rules out the main root cause being no vacuum advance? Though I’m sure it would help me to find one. I believe my Weiand intake doesn’t accept a factory vacuum advance distributor, so I’ll have to verify that.
I’ll read up more on the articles you guys have mentioned. Thanks for links. I don’t know for sure what the distance is between the impeller vanes and the backing plate. So that’s something I could look at.
dont test it idling....you need to drive it....air needs to go thru radiator at 35 mph or so...where would you ever sit 20 minutes idling? 220F at 20 min idling I would call "normal"...go drive it....THEN you can see the real world
Yes I agree, it's important to test for both idle and moving, but I couldn’t take it for a drive, the seat belts aren’t all in and I was watching the kids, so I couldn’t go anywhere. None the less, I had the same problem while test driving the car previously, so driving or idling, it reaches too high of a temp.
I could sit idling on the Los Angeles freeway for longer than 20 minutes; all you need is one accident ahead of you at rush hour. I've experienced it plenty of times. So I need the car to be able to withstand 90 degree ambient temperature and at least 20 minutes of idling.
I had a 76 firebird with a 400 and it never hit these kinds of temperatures. Yes, the 455 is hotter, but again, the 455 cars worked fine from the factory in California, just like the 68 400s with air conditioning worked fine in California when they were new.
I think I just need to look at each part of the cooling and timing systems and make sure their dialed in. I want to keep it under 200 degrees at all times. At the most, it should never reach the boiling point of 224 degrees. I think that's possible if everything is set properly.
Personally I feel the idle test is more telling that the driving test. From everything I've read about Pontiacs, it's usually the idling that makes them run hot! So basically if our FGF can pass the idle test, they should be ok driving.
I still watch the temp gauge every time we drive on the beach as it is usually very warm (90* yesterday) and it is total stop and go bumper to bumper for miles upon miles. I am feeling pretty good about my Bird now after all the years of running hot.
It's a great feeling once you get to the point where you are fairly confident with your car. I know for me that was not the case for the first 7 years of owning the car!
Yes I agree, it's important to test for both idle and moving, but I couldn’t take it for a drive, the seat belts aren’t all in and I was watching the kids, so I couldn’t go anywhere. None the less, I had the same problem while test driving the car previously, so driving or idling, it reaches too high of a temp.
I could sit idling on the Los Angeles freeway for longer than 20 minutes; all you need is one accident ahead of you at rush hour. I've experienced it plenty of times. So I need the car to be able to withstand 90 degree ambient temperature and at least 20 minutes of idling.
I had a 76 firebird with a 400 and it never hit these kinds of temperatures. Yes, the 455 is hotter, but again, the 455 cars worked fine from the factory in California, just like the 68 400s with air conditioning worked fine in California when they were new.
I think I just need to look at each part of the cooling and timing systems and make sure their dialed in. I want to keep it under 200 degrees at all times. At the most, it should never reach the boiling point of 224 degrees. I think that's possible if everything is set properly.
I totally agree with your theory of when our cars were new. This is one of the reasons I've decided to go total stock on my car as IMO that most issues begin when you start modding/upgrading etc. The fact that once I did get back to stock my problems with running hot, hard starting, running rough, over charging/under charging etc. all seemed to come to an end...
Don"t get stuck on that 224 degree boiling point. That why the cooling system is sealed...to build pressure to effectively raise the boiling point of the cooling fluid. I'm sure someone has the actual numbers o this, ie: each pound of pressure raises the boiling point by X degrees. The original "HOT" light on our 'birds did not light up until 246 degrees...
EDIT: I just reviewed your original post. IMO, the 3 core rad ain't gonna do it for your 455...ever.
Last edited by Bronze Bird; 04/13/0911:15 PM.
I'm a hobbyist. Not a professional. Don't be hatin'!
Yeah I wrestled with a totally stock motor versus adding a few modifications. In the end, the speed bug got me and I decided to go with a cam that has a higher lift, 1:65 rockers, a different intake, and carb. I wanted to make sure the engine could breathe once I put better heads on. I never did get better heads. Right now I have the factory 6X heads that were re-done. I did go 10 over too, to clean things up. Beyond that, it’s a standard rebuilt 455.
Another thing is that I'm using the timing cover from my 68 350, to keep more of an authentic look. I'm not sure if that would cause any issues.
So the 3 core won't work for the 455? It worked for my 350 with air conditioning, so I thought it would work for a 455 without air conditioning. Could I take it to radiator shop to have the flow tested to see if it's flowing enough? Or is there just a general rule that 455s are too hot for a 3 core?
I don't know for sure what rad came with the 455. I do know that many use the 4 core with 400's with some success... I use a brass/copper 4 core on my modified 400/468(same as previously unmodified 400) and it has been adequate during the cooler part of the year(since November). It will get a more thorough test as the temp rises over the next month or so.
That 455 is going to produce alot more HP than your 350...and consequently more heat. Others may disagree but, I don't see how the rad designed for the 350 will cool the 455.
Just my opinion...
I'm a hobbyist. Not a professional. Don't be hatin'!
I don't think you want to go smaller chamber size heads than 6x on a 455. That will create too much compression for pump gas. I think the timing cover is the same for 350-455 and I don't think it makes a difference. I'm not completely sure on that.
As for the 3core rad, I think Bronze Bird makes a good point with that. If you were driving at cruising speeds at no stop and go, MAYBE a clean, good flowing 3core rad would work. Since you mention you will be driving in much stop and go heavy traffic, I would suggest upgrading to a 4core aluminum rad.
With vacuum advance, it works with light load or cruising conditions. At full throttle at or above 3000 rpm, the vacuum advance reverts to mechanical advance and vacuum advance is lost. As we talked about before, that is something to look into.
"An ignorant man thinks he knows everything, a wise man knows he doesn't."
