car getting hot, need help/ideas

I have a good friend who had trouble last night with his 40 running hot and boiling over. It is a strong 302 with an electric pump. He ran this car without problems last fall then I pulled his engine to freshen it up after an unrelated issue. So the system has proved to cool the car, the pump is running and the fans are working. It is barely 30 degrees outside and when he gets on it at all it heats up to over 220. There is a chance that the water level was low or an air pocket. Other than that, what else could we check? Maybe I have missed something obvious.
 
Dean, maybe check the coolant mix. I only run about 30% antifreeze, mostly for the corrosion package, and some water wetter. Other than that recheck the plumbing. I'm sure you guys have the bleed lines from the top of the radiator and the from the intake manifold but thought I'd mention those. Is he running a thermostat? Maybe not enough dwell time in the radiator.
 
I will check the timing. I set it at a very safe 32 degrees but it might have moved. If I forgot to tighten the dizzy and it moved it would likely retard the timing correct? I would think that would cause the engine to run cool or is that logic backwards? I think it is very likely an air pocket. I had my friend fill the radiator when he got home and it took on a lot of water. He started the car in the garage and it jump to 200 degrees and stayed there for 5 more minutes as the car spun at 3 grand. It might be just that simple but I wanted to hear from all of my respected automotive peers hear on the forum to create a list of things to check tonight when I have time. I am running a 180 degree thermostat. I will also bleed the air out of the intake just to check that as well.
 
Dean
I had a little problem of this nature straight after fitting the aircon. the car overheated on the 25 mile journey home. It took several attempts to bleed the air out of the system (fill up, run and let air out of the radiator bleed tap). Once I had done this though the temp remained at normal and has never gone wrong since. I think if you have disturbed the cooling by carrying out work then an air lock is the most likely reason.
Chris
 

Randy V

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Air-pockets are your worst enemy... Pumps can pump and temperature probes are inaccurate when in an air pocket...

Since the cooling system worked well in the car with the last engine - I would have to think that the design / configuration is not the cause..

That said - I know how many times I've run into 302's with headgaskets that won't hold under pressure although they are fine at low loads and low RPMs..

I've changed my strategy on 302s a few years back and have had zero problems since.

Using either headbolts or studs - I torque them down ~20 Ft Lbs at a time in a radial pattern starting in the center and I end up with 80# on the top row and 70# on the bottom row.
If using bolts, I put Teflon thread sealer on all bolts (even those in the blind holes) in order to get a more accurate torque reading.
I do not re-torque the bolts after the first heat cycle..
This has worked well for both street and competition cars.
 
I had the same problem..I had air pockets!!!! it took several times to purges the system. I purge the system a couple of times and still had to do it 2 more times. MAKE SURE ALL YOUR CAMPS ARE TIGHT!!!! IT WILL SUCK AIR EVEN IF THERE IS NO WATER LEAKES.!!

MY 2 CENTS JOHN
 

Chuck

Supporter
Dean:

At the risk of being redundant, and a bit corny, I did a couple of additonal things on my 302. (1) Loosened the temp sensor sending unit just aft of the thermostat cover to let the air bubbles bleed out as it was warming up initially. (2) Here is the corny one: I jacked up the front end of the car so that the front of the engine was much higher than the rear thinking this would help purge out any air via the temp sensor ( see #1).

Corny, but it seems to work.

On the other hand, just cycling it through a few warm up cycle seems to have worked as well although not as quickly.
 
The cooling systems of mid-engined cars are compromised by the fact that the water has to go down from the motor, then forward about a mile, then up into the radiator. Filling the car on level ground and purging all the air out is therefore just about impossible.

Elevating the rear of the car a foot or more to raise the pressure tank that much more is crucial. You'd be amazed how much air can be hiding in a 'full' cooling system. Also, bleeding the cooling system is an iterative process; you'll crack the bleeder and top off the pressure tank while the engine is running and the thermostat open, until you get a solid stream of water out of the bleeder on the radiator. Cap the system, shut the car off, let it cool overnight. The next day, you'll get a big burp of air again. It usually takes 2-3 cycles of this process to get most (not all) of the air out.

Having said all that, a car that suddenly overheats probably has another problem. If the distributor gear shear pin shears (which is usually caused by a piece of debris getting trapped in the oil pump, which jams it momentarily), the gear can spin slightly on the shaft and then catch, so the engine keeps running, but the timing is desperately retarded. So that's something to check too.

Good luck!
 

Randy V

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Air-pockets are your worst enemy... Pumps can pump and temperature probes are inaccurate when in an air pocket...

I had meant to say that pumps CAN'T pump when in an air pocket...
Darned fingers have almost entire quit working at my command...
I suspect they've joined the union!!!! :furious:


One thing I intend to do with my intake manifold is to drill and tap bleed ports at the rear of the intake for the cylinder heads... That should also be a good place for trapped air to accumulate...
 

Rob

Lifetime Supporter
Dean,
With respect to the concern for air pockets.....I too had a similar scenario with my small block. The temp would be fine, then next thing I knew it would spike. It could be fine for quite a while too. The concern became most obvious while on my first dyno run for some reason. Note, I had run on track a few times prior too......with no issue. In efforts of making the set up as robust as possible I went through the process of plumbing in recirc lines and re-routed the air vent system that I had in place already.

To Mark's comments about manually bleeding air, based on my experience above, I believe manually bleeding does not provide a long term solution. As your coolant gets aerated during running, the air bubbles can then collect all over again in those trouble areas of the system. I believe this is why I was initially good to go, but then the monster would rear it's ugly head at any time.

Essentially my fix was as follows, the air bleed lines from the back of the intake and front of the intake (hot water neck for heater core) joint together and go to the top of the reservoir tank. Then a line from the bottom of the tank goes toward the motor and the radiator air bleed lines join it, then continue to the water pump (the return water heater line). It worked perfectly. Temps didn't go over 185 on the dyno.

Hope this helps.....
 

Pat Buckley

GT40s Supporter
What does the temp guage do when it overheats - does it suddenly shoot up or is it a gradual thing? IOW, is it more of a fluctuation?

It has been my experience that relatively rapid movements of the guage are more indicative of an air pocket/bleeding issue.......

A steady slow rise is more usually caused by something else like a plugged radiator, insufficient cooling capacity, timing, etc....
 

Ian Anderson

Lifetime Supporter
When you frehened the motor did you put in a new thermostat?
If so is it acually working or being too restrictive? Extra hole drilled / jiggle pin in outside flange to aid flow before thermostat opens and allow bubbles to crear from this area?

Secondly
Are you running a cockpit heater? Was the tap to this open? If so is there too much flow through this resulting in not enough flow through the radiator. It was a problem encountered on the MGB and it was found the cooling of the engine was better with the inside heatr turned off to stop the water flow and force it ALL through the rad,

Ian
 
Well, we are still chasing the problem. The car has an electric water pump without heater line ports. The expansion tank is plumbed into the small bypass outlet on the thermostat housing. We didn't know where else to put the fill line. I seems that when the car first starts, it is fine but when it starts to warm up, water starts shooting out of the expansion tank. Could the electric pump be wired wrong and flowing back wards? Logically it seems like water would be forced out of the tank BEFORE the thermostat opened, not after the car heated up. I will also add the it seems that the heat builds pretty fast in this car. We are still loosing water and the car still overheats. The plugs seem oily so I don't think it is a head gasket but I haven't ruled it out. Any ideas???:cry::cry:
 

Ian Clark

Supporter
Hi Dean,

There's some great info in the Meziere Catalogue. You can download it here: Catalog Download , check out pages 47 on. Hope this helps sort out the plumbing. Probably over 90% of GT40 cooling issues are air pocket related, the other 10% is just to keep you on your toes.

Cheers
 

Ian Anderson

Lifetime Supporter
Dean

My understanding is that the outlet from the header should go into a T in the pipe coming back from the Rad (slightly lower pressure so it will draw the fluid down from the header)

The inputs to this tank are from the various bleed areas of the system and enter above the header tank water level to allow bubbles to end up at the top of the header tank. This uses the header tank also as a swirl tank to remove excess bubbles from the system.

If it is connected to the small outlet on the thermostat housing and the thermostat is closed and the pump running you will be building up a pressure directly against the header tank / pressure cap and could basically just pump water past the pressure cap.

So my understanding is that you have it plumbed into the wrong area on the cooling system

Ian
 

Randy V

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Is the water pump a remote pump or is it bolted to the block?

Your header tank should be connected to the suction side of the water pump either way. All hose connections to a water pump lead to the center or inlet side of the pump. As a rule - water pumps "Suck"...

On a conventional water pump, you'd connect to either of the smaller pipe fittings on the pump (Heater hose / Bypass hose).

NAPA has a kit that will show you if you have any combustion gasses getting into the cooling system. It's referenced in this link;
Head Gasket or Combustion Leak Test Procedure (Gasoline Engines Only)

also check here;

NAPA Online PartsPRO SE

BTW - yes, if you leave a distributor loose, it will rotate in the direction of the shaft which would retard the timing.
 
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Russ Noble

GT40s Supporter
Lifetime Supporter
Ian and Randy have, I think, hit the nail on the head. If the header tank does not have a return (needs to be about 5/8") to the suck side of the pump, then you'll never keep it cool. If it was OK before you fixed it, :laugh: then there must have been no thermostat fitted, or it was faulty and not closing properly.
 

Jim Rosenthal

Supporter
It's possible, on a small block Ford motor, to install a cylinder head gasket "backwards" so that the motor will run (good compression) but the water flow on that side will only go past the first cylinder. The gasket is made in such a way that the water has to flow along the cylinder head, then down into the block through holes in the gasket, along the block, and out of the engine. If you had a cylinder head off and did not install the gasket exactly right, the engine will run but that bank of cylinders will overheat VERY quickly. (this happened with the engine in my Kirkham which was built by a person who will remain nameless) We had to pull the head and install a new gasket- oriented the correct way. It has run fine ever since.
 
I'm not sure why someone has not put a sketch of a system that works so I will. My car has a 375~400 horse 302 and runs at 180~185 while driving and will sit and idle until it runs out of gas. The fan will come on when it's sitting and cool it from 190 back to 165~170 and will shut off. I will tell you that for the first four or five drives after filling the system and bleeding it the best I can, I get temp spikes from steam pockets up to 220 for a few seconds at a time. (it seems like a lot longer with the temp that high but it's not) After a few 20 minute drives it seems to normalize and no further problems. I hope this is of some help to you and good luck. I got this picture off the forum a while back, it's not mine but I used it and it works.

Steve
 

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