running hot
 

my project truck is finally able to start. I remember when I bought it, it got hot in traffic and at stop lights, but did not over heat on the freeway home. So now I'm working on the engine in the driveway at idle and it gets hot pretty quick, almost to the red in less than 10 minutes. (does anyone know the numbers on the stock gauge, how hot is it when it first hits red, and where should it stay, around the middle?)

It seems like it takes a long time for the thermostat to open, but it does open. I remember changing it (185), and thinking back, I forgot to check for the arrow pointing to front, is that a big deal? And it is doing pretty much what it was when I got it, should I take that apart?

Other info: a/c was added to the vehicle, don't have that belt on now, but there is a condenser in front of the main for the a/c. Maybe that's blocking the air? That a/c fan is not coming on (vehicle has a regular mechanical fan,though), but then again, the a/c is off. Also, when the engine is idling, I hear a noise, much like a power steering pump low on fluid. Not real loud, but it is definitely there and coming from the engine, probably the front of the engine. If my water pump would going, I'm thinking gm water pumps have a seep hole, and I'm not losing fluid, so thinking the water pump is ok? Timing is at 0 at idle.

Re: running hot
 

How old is the radiator?

If it's the original 40 year old radiator... it probably needs to either be rodded out, core replaced, or the whole thing replaced.

Gary

Re: running hot
 

Unless that A/C condenser is badly plugged, it won't block airflow significantly. Is it actually overheating, or is it possibly a bad reading on the gauge? Could be a bad gauge / bad sending unit.

Re: running hot
 

thanx replies. I have no idea age of radiator, i see it has been welded around the neck, probably pretty old. I drained it, does not look toooo coroaded from what I can see, fluid is new. I does not leak. Condenser does not look too plugged.

It hasn't blown over, but sure seems really hot. gauge moves to just below red, and back down as it cools. not sure how I can test that.

Re: running hot
 

Does it have a shroud and where's the fan in the shroud?
Original fan?

Re: running hot
 

if it heats up fast, the thermostat should open up fast once it gets to 185. get a cheap mechanical temp gauge at your local auto parts store and see what it reads. you don't have to put on dash, just let it lay by the engine . if it reads normal temps, either mount it at the dash or remove it and hook the other one back up..

Re: running hot
 

Four things I would do in that situation:

1] Check coolant viscousity with a squeeze-bulb gauge. Prestone makes one that's about $5 in all auto parts stores. Hygrometer, I think? In Miami, you won't need as much polypropylene-glycol as someone in Minnesota. You could maybe go 55% water--45% antifreeze, or 60/40. You don't need to worry about the block freezing.

2] Radiator caps go bad over time. Buy a good new one. You want a 16 PSI cap, since you have an A/C system. Even if it's inactive.

3] I ran an AutoMeter mechanical water temperture gauge because I had problems with the OEM electric temp gauge. Much better temp indication, and not dependant on voltage.

4] Try a 160* thermostat.

Re: running hot
 

me i'd go to the super market and buy a cheap thermometer and take the temp of the coolant and find out exactly what hot is hot and a `160thermo wont make it run any cooler so save yerself that moneyr

Re: running hot
 

Timing is Zero at idle? That could be a factor in overheating... I think since yours is pre emissions you may want to try looking into whether you need all of your vacuum advance (BTDC) to be in at idle provided:

1.) you are using full manifold vacuum at your vacuum advance unit - and
2.) you are using a Vacuum Advance unit that maxes out at 2Mg below the vacuum produced by your engine at idle.

If you are using a vacuum advance unit that is stiffer than that produced by your engine at idle (or say 50 RPM above) and does not max out at 2" Mg below what your engine produces at idle then things will be different

Also If you are using ported vacuum then things are different

Be advised I am not familiar with your particular engine but I use this is a general starting point and if you get pinging then removing that takes precedence because things tend to wear out and the tolerances stack up..

This is just how I think about this and not what I am advising anyone to do - also since I don't know your set up there are hundreds of reasons my suggestions could be completely wrong..

Try a search on Google or on this site for "Idle Cooling" and maybe the term "Timing"..

Re: running hot
 

Yeah, I agree, 160* t-stat won't help.

As asked above, is there a fan shroud? And what type fan does it have?

Re: running hot
 

Crazy things happen but it sounds like your thermo is in upside down. 😁
Posted via Mobile Device

Re: running hot
 

Pull the stat and make sure its installed correctly, re time to 12 degrees before top dead center with the vacuum line unhooked from the distributor and plugged it so no vacuum leak to the carb.

There is a weep hole on the water pump but a noise could be a bad bearing. or bearing on the alt?

Per CDowns suggestion, don't pop the rad cap to check the temp unless you want to take a scalding hot shower in coolant, an option would be to open the radiator petcock and drain some into a container.

Re: running hot
 

old guys xare smart enough to remove a radiator cap without getting burnt young guys oh well gotta learn sometrime

Re: running hot
 

Don't remove the radiator cap when hot, there's no "safe" way to do it no matter how old you are. Let those that claim otherwise keep at it, but don't imitate. I know someone who tried and failed, and fortunately only has minimal facial scarring.

- Make sure timing is set correctly, at least 6-8 BTDC, ideally a little more these days
- Make sure your fan clutch is working correctly, dragging when hot
- Make sure your fan shroud is in place and sealed up

If you don't have a shroud or you have some bogus flex fan in there, all bets are off. You need at LEAST the factory parts in place for the engine to cool properly.

Re: running hot
 

Yep, it can be done -- that's just one of the things I learned in my part-time service station job before I was old enough to drive. :lol:

Re: running hot
 

Come on you clowns, you're going to get someone scalded like there's a secret to safely taking a rad cap off.

If you're talking about draining fluid from the petcock until there's no pressure left whatsoever, say so.

Just making it sound like if you're manly enough and old and wise enough you can just take the rad cap off a hot engine isn't fair to someone who might not understand you.

Re: running hot
 

Clowns?? That's a bit harsh and judgemental, don'tcha think? I could call you names too but that seems a bit childish.

It has nothing to do with being manly or old. It's just common sense. I have done it safely many times and can explain how I was taught. If someone tries it and fails, that's entirely on them.

You need to cool the radiator. With the engine idling, run cool water over the top of the radiator and spray the cooling fins. It takes a few minutes. When you think it's cool enough, slowly gradually carefully crack the radiator cap open. There will still be pressure and you can still get scalded. Protect your hand with a glove, shop rag, anything -- the more the better -- between you and the cap. At this point you are not removing the cap, just cracking it open to gradually release pressure. You may need to run more cool water over the radiator. Once you can loosen the cap without hot water or steam escaping, it's safe to remove the cap.

Hope that wasn't too much for you to deal with....

Re: running hot
 

Nope. My mom was a burn ward nurse. You see things and hear things and meet patients and you'll take them seriously too.

EVERY single severe burn patient eventually comes to the admission of "The mistake I made was", and I don't want someone on here to be scalded because people with bravado wrote about doing dangerous things with impunity.

If I save one person from a burn while annoying 50 others, I'll take it.

No, you typed real slow so that I could read it. I'm not endorsing it but since you included an explanation of HOW you do it, I think that's far better than leaving people to guess and fail, right? Sort of all I asked, so thanks.

Re: running hot
 

:lol:

Gary

Re: running hot
 

First, I have taken radiator caps off of hot engines, and can do it safely. I hate to see an argument about this, but I do know that you have to be careful with advice. A shop teacher once told me a story about when he told someone that if you could turn the pulley on an alternator, the belt was too loose. Some fool tried it with the engine running and ended up with a mangled hand - so you have to be careful.

Anyway,


Thanx for all the replies. To address some of the points:

1. the radiator cap is new 16psi.
2. the coolant is new, 50-50 with distilled water
3. I guess a cheap mechanical temp gauge is not a bad idea, not sure how or where to hook it up? I really do think the engine is getting too hot, after years of tinkering on cars, I just think it is.
4. suprized on the timing advice. I looked it up, and I'm pretty sure it said 0 is the required timing. I did the timing with the vacuum to the distributer plugged. The vacuum is the only vacuum port on the engine, and it comes from the base of the carb. I will retime it.
5. @ swamp rat: I'm gonna reinstall the thermostat. I tend to agree that the alternator is most likely the sound I'm hearing. Bummer, one more thing to replace.

6. as far as the shroud, I have none, just a little thing on the very top to keep you from touching the fan. The fan appears stock (I have no idea) non-clutch, non-flex. It has a spacer and is about 4 inches from the radiator. I have what appears to be a 2 core radiator.

Should I get a shroud? Do you gentlemen think my fan is sufficient?

thanks again.

dave

Re: running hot
 

From your first post:
Given its history of getting hot, I would definitely recommend a shroud and a thermal clutch fan.

Re: running hot
 

You have a 6 cyl, those never came with a fan shroud, only what you mentioned. There are lots of guys running that dinky little finger saver and their inlines don't overheat. While there's nothing wrong with a shroud and clutch fan and in fact, it's a great addition, it seems as though there's still something wrong. I'd hate to see you invest money in a band-aid first, rather than a solution. A shroud and clutch fan could possibly keep the engine cool enough to operate, but aren't necessarily the cause of the overheating issue, IF in fact, it's a mechanical fault and not a faulty old gauge.

Re: running hot
 

On the V8's you can just pull the upper radiator hose and look down the neck of the thermostat housing to verify that the thermostat is installed correctly... to me that would be easier than pulling the housing itself.

Especially if use Gascacinch or other sealer on those thermostat cover gaskets..

Another possibility is an air bubble in your cooling system - on the small blocks some advise drilling a 1/8" hole through the thermostat to help bleed the air out when filling the system; but it is not necessary.

I'll try to attach a PDF below to help with more details on setting the ignition timing.

If you are using the original timing advance spec from the late 1960's that was for leaded gas.

The best advice in my opinion came from Bruce's write-up about timing from his "Its Just a Pickup" build page (around page 27 of that? somewhere around there).

Its for a 72 SBC but his process for setting ignition timing is super logical and excellently written.

Re: running hot
 

Here's the links to Bruce's write-up on ignition timing.. the first one was post #712 of his build page and you'd also want to read his follow-up which was shortly thereafter..

Many thanks to Bruce for all he has helped with his efforts!


http://67-72chevytrucks.com/vboard/s...&postcount=712


http://67-72chevytrucks.com/vboard/s...318544&page=29