problem NOT solved! HELP

[BarryK]

ok, sorry to be a PIA but ................
My car has been running hot. Last year it ran it rock steady 180* no matter the driving conditions or how hot the weather was outside.
Now it's running an average of 200* - 220*.
I redid the timing per Lars' article and just replaced the t-stat.
Just sitting in the garage running for 5 minutes warming up while I was double checking the coolant level after refilling it got up to around 215*-220* that quickly. I drove it a short ways to see if the air flow from driving would help cool it down but it didn't. Still staying at 215* - 220*.

Someone suggested I double check my heater hoses in case the "mechanic" last week accidently switched them around but they are correct.


What else do I try to look at to fix this problem?

 

[61 Silver]

Hi! Barry

When the engine is hot have someone turn the engine off and count the revolutions of the fan. It should be four to five revolutions only. If it free wheels it could be a fan clutch problem.



I would also have it checked with a temp gun to insure that the gauge is accurate.



Check the radiator fins to insure there is no dust from paint or body repairs blocking air flow, you may want to take an air hose and blow from the engine side, do not damage the fins.



Ray

 

[Jeff Farrar]

Make sure your vaccum can is "working". Just becasue it is hooked up doesn't mean it is working. How much timing advance do you get when you hook up the can vs. with it plugged. Check the model number on your can and make sure its advancing the correct number of degrees vs. spec. Also, what vaccum reading do you get at idle? If you have a leak somewhere that would not let you can advance your timing all the way. Lars has good vaccum can paper with specs in case you need a new one matched with the old.

 

[ctjackster]

ditto on the advice as to verifying the temp gauge reading with a "temp gun" (an infrared sensing device), although the year to year comparison makes me wonder what has changed. Perhaps certain items have deteriorated - fan clutch, vacuum can function, water pump, etc . . . .

 

[BarryK]

Ray
that's not good news......
if I start the motor than turn it off (just did it since the motor is still very warm) it spins a LOT more than 4 or 5 revolutions. It spins for a good 15 secs or so until it stops.

supposably the mechanic last week checked the system with a IR gun and said it was pretty accurate to the guage - only off by a few degrees.

There is a slight amount of dust on the fins but bot what i would a lot or an excess amount but i'll try cleaning it off later. I don't have an air compressor to blow air, so will a water hose do the same?

 

[BarryK]

Jeff
I know the can is working because there IS a difference when I disconnect the vacuum line from it. Whether or not it's the correct can is another story. I got it from LICS last year when I had the distributor rebuilt.
It has the number 236 on the bracket but I know nothing else about it.
I don't have a vacuum gauge to measure the system - I tried to get one at sears and at the parts store the other day when I got the timing light but neither store had one - go figure!
I think i may have Lars paper, i'll check

 

[BarryK]

Jack
I was told the mechanic last week checked it with an IR gun and he pronouced it accurate within a few degrees but with the 'quality" of the other work he did anything is possible.

 

[Subfixer]

Barry,

Had the same problem with my fan clutch. New one fixed the low speed/idle heatup.

There's a WHOLE lot of stuff that has to work correctly to keep the temps down (timing, radiator, fan, shroud seals, etc.....). I see you are finding that out as I did. I ended up replacing or adjusting everything..... it was ALL bad.

Now it runs 180-200 with AC on and outside temps at 90* and 95% humidity.

 

[ctjackster]

Barry,

Had the same problem with my fan clutch. New one fixed the low speed/idle heatup.

There's a WHOLE lot of stuff that has to work correctly to keep the temps down (timing, radiator, fan, shroud seals, etc.....). I see you are finding that out as I did. I ended up replacing or adjusting everything..... it was ALL bad.

Now it runs 180-200 with AC on and outside temps at 90* and 95% humidity.

not sure which fan clutch my pal Paul bought (I suspect he told me once and I forgot) but the GM-spec fan clutch is again showing available from GMPD:

GM PART # 3916141
CATEGORY: Engine Air Cooling Fan Clutch
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $196.70
OUR PRICE: $112.12
DESCRIPTION: CLUTCH

plus S&H, of course!

should you start thinking you need a new one - but check yours out first before huling off and dropping $130 on a new fan clutch. And if you do see the need to replace it, this is something you and your set of wrenches can tackle, Barry.

 

[BarryK]

Paul, Jack

we know the timing was just done so hopefully that's still not an issue.......

radiator and fan shroud look new so I suspect they were both replaced during the restoration just before I bought the car - can't imagine the radiator going bad after only approx 1500-2000 miles.

any way to actually check the fan clutch to see if it's working correct or not? The free spinning compared to Ray mentioning that the fan should only go 4-5 revolutions after turning off the motor has me concerned now.

I was just on the phone with a buddy and he used to race a 1970 Z28 years ago. He suggested there might be an airpocket in the system keeping the radiator from filling up all the way with coolant? he also mentioned that the heater box holds a bunch of coolant and that something may be keeping that from getting back into the system?

One thing I noticed when following Pauls advice on refilling the coolant is that I left the cap of the expansion tank off while the car was running and warming up in the garage and watched the coolant level. When the temp rose to 180 and the T-stat should be opening I didn't see the coolant level drop at all even after the temp got to about 210-215*. Should I have seen the coolant level drop if the t-stat opened?

sorry for all these questions! I need to get this resolved by next Wed. If I don't I'll have to cancel going to Carlisle because I don't want to risk driving the car that far with temps this high

 

[ctjackster]

of course, you will then start to wonder (let me plant the seed for you) if you installed the t-stat backwards . . . . .

 

[BarryK]

of course, you will then start to wonder (let me plant the seed for you) if you installed the t-stat backwards . . . . .

no i didn't!
I installed it the same way the old one was in there. really, I did!

the metal loop with the pin under it went on top and the thicker barrel part with the spring around it with on the bottom.

 

[Mike McKown]

Paul, Jack

we know the timing was just done so hopefully that's still not an issue.......

radiator and fan shroud look new so I suspect they were both replaced during the restoration just before I bought the car - can't imagine the radiator going bad after only approx 1500-2000 miles.

any way to actually check the fan clutch to see if it's working correct or not? The free spinning compared to Ray mentioning that the fan should only go 4-5 revolutions after turning off the motor has me concerned now.

I was just on the phone with a buddy and he used to race a 1970 Z28 years ago. He suggested there might be an airpocket in the system keeping the radiator from filling up all the way with coolant? he also mentioned that the heater box holds a bunch of coolant and that something may be keeping that from getting back into the system?

One thing I noticed when following Pauls advice on refilling the coolant is that I left the cap of the expansion tank off while the car was running and warming up in the garage and watched the coolant level. When the temp rose to 180 and the T-stat should be opening I didn't see the coolant level drop at all even after the temp got to about 210-215*. Should I have seen the coolant level drop if the t-stat opened?

sorry for all these questions! I need to get this resolved by next Wed. If I don't I'll have to cancel going to Carlisle because I don't want to risk driving the car that far with temps this high

If you could still see anti-freeze in the intake manifold when you changed the thermostat, I wouldn't exspect the level of coolant to drop maybe a small amount in the surge tank when it warmed up.This usually only happenes when the block/heads have been drained. In any case, when the engine cools, it should burp and the coolant level will drop if it has air in it. Some will tell you that they fill the engine through the thermostat opening to purge air out of the system. I've alway filled through the surge tank and haven't experience any difficulty.

If your fan is in fact rotating like you say after you shut the engine off, that has to be a contributor to your problem, if not the sole cause. With the engine hot and idling, you should be able to feel a stiff breeze if you hold your hand behind the fan blade. Rev the engine and the air velocity increase should be proportional to the increase in rpm. If it's not, I'd say your fan clutch is defective.

Didn't one of your other posts say you bought an IR gun? If you did, shoot your own readings. Tell you what. If you're not sure if your engine is really overheating, simply take the surge tank cap loose (to the first notch) so the cap can't blow off and start the engine. Before your temp guage gets to 220, you should have coolant bubbling out of your surge tank and running out of your overflow hose on the ground if you are really running over 212.

Be careful.

 

[JimVette]

A couple of questions. You mentioned a restoration. Has this happened since the restoration and not before. During the restoration was the clutch replaced. I had a '66 327/350 that suddenly would run hot in slow traffic (parades) or after warm-up in idle. It turned out to be a dragging pressure plate. I only discovered this was the problem after replacing the clutch 6 months after replacing it orginally and I had some pretty good engine people scratching there heads over it.

 

[Subfixer]

any way to actually check the fan clutch to see if it's working correct or not? The free spinning compared to Ray mentioning that the fan should only go 4-5 revolutions after turning off the motor has me concerned now.
One thing I noticed when following Pauls advice on refilling the coolant is that I left the cap of the expansion tank off while the car was running and warming up in the garage and watched the coolant level. When the temp rose to 180 and the T-stat should be opening I didn't see the coolant level drop at all even after the temp got to about 210-215*. Should I have seen the coolant level drop if the t-stat opened?

Barry, The fan clutch check that you did is correct. The only other check you could make is while the car is HOT, turning off the engine should result in the fan continuing to spin 2 revolutions or less (my new one stops about 1/4 revolution). Any more than that and it's time for a new fan clutch. The item Jack mentioned is the one I bought.

As far as the coolant level, it's possible you have some trapped air, but I doubt it. The bypass hose from the intake manifold to the top of the waterpump does a good job bleeding out the trapped air. The low HP cars don't have this hose and sometimes air gets trapped behind the thermostat (not heating it enough to open).
I can usually see some coolant movement from where that small hose enters the tank when the T-stat first opens. Once all the air is purged out, I don't normally see much coolant movement in the tank.

 

[vette-dude]

I vote it is the clutch Fan. I would bet you can beat the GM cost at any auto parts store!! It shouldn't freewheel as much as you said it does. If you don't mind not being OEM original you can replace the clutch fan with a flex fan and it will cool down the motor better. Good Luck.


Randy

 

[BarryK]

thanks for responding Mike

no, when I removed the t-stat housing I could not see any coolant so the level must have been low enough to have taken it all out of the manifold.

I checked the fan as you suggested. As i rev the engine I can feel it blow air harder.
at idle, there is not what what i would refer to as a STIFF brezze, just barely some air movement. As i rev it it will increase but it's not as much as i would have expected but never having done it before I have nothing to compare against.

No, I don't have an IR gun. I treid to get one at Sears the other day but they don't carry them or didn't have any in stock.
I restarted the motor and actually took the cap of the expansion tank off completely than waited for the motor to warm up. once it reached 180* according to the gauge I started watching the coolant level. I didn't see any change in the level at all that I noticed either going up or down. The temp reached just barely shy of the 220* mark on the gauge and still no change that i saw in the coolant level - MAYBE just a tab bit down, MAYBE, but I can't say for sure 100%.
No coolant surged out of the tank or the overflow tube. I than reinstalled the expansion tank cap and just let it sit and idle for a while more. Temp stayed right at the point just barely shy of the 220* mark and wouldn't move any further which at least is better than fefore when it almost pegged out the 240* mark at traffic lights.

so, from what I can piece together, either the fan clutch could be shot or the temp sender is inaccurate and the mechanic lied about checking it with an IR gun when he said he did. Would these conclusions sound correct?

 

[BarryK]

A couple of questions. You mentioned a restoration. Has this happened since the restoration and not before. During the restoration was the clutch replaced. I had a '66 327/350 that suddenly would run hot in slow traffic (parades) or after warm-up in idle. It turned out to be a dragging pressure plate. I only discovered this was the problem after replacing the clutch 6 months after replacing it orginally and I had some pretty good engine people scratching there heads over it.

Jim

the restoration was completed just before I bought the car last year. Only drove it a few months than sent it to the paint shop (paint was not done during the body-off) where it has spent the last 10 1/2 months. I just got it back 2 weeks ago. I cannot answer whether or not the clutch was replaced during the restoration BUT when it was at the mechanics last week he "adjusted" the clutch he said because there wasn't enough play in it according to him.

 

[BarryK]

Barry, The fan clutch check that you did is correct. The only other check you could make is while the car is HOT, turning off the engine should result in the fan continuing to spin 2 revolutions or less (my new one stops about 1/4 revolution). Any more than that and it's time for a new fan clutch. The item Jack mentioned is the one I bought.

As far as the coolant level, it's possible you have some trapped air, but I doubt it. The bypass hose from the intake manifold to the top of the waterpump does a good job bleeding out the trapped air. The low HP cars don't have this hose and sometimes air gets trapped behind the thermostat (not heating it enough to open).
I can usually see some coolant movement from where that small hose enters the tank when the T-stat first opens. Once all the air is purged out, I don't normally see much coolant movement in the tank.

hmmmmmm
everything is now pointing to that fan clutch........
expensive part
how hard is the removel and reinstall of it?

 

[allcoupedup]

Barry - I picked up a generic thermostatically controlled fan clutch at Autozone for $35. Eaton replacements are the best you can buy but since I am a cheapo I went with a generic replacement. I believe your vacuum advance can should be marked B28 since you have an SHP motor.

Brian