Is it possible I have the wrong waterpump?

[regularman]

Hi guys. I haven't been on here for a while dealing with all that bothersome non spridget stuff called life. Anyways, its cold weather here and I thought I might attempt to dig into my weird overheating problem on the midget. After the car has been sitting and not run for 3 weeks, when I remove the radiator plug there is air pressure still in there. In most normal systems, if the water got hot then it would force it into the overflow and then out the pressure cap and when it cooled it would draw back in from that tank and refill the sytem and the radiator would never get low. With a full radiator of water the car runs nice and cool, but once it gets heated up one time, like in a hard pull up a hill, it starts to run hotter and hotter until it would boil if not shut off. I put a new water pump on it when I went through the engine, the head gasket is new and the engine block and head were in great shape when I checked it. The radiator is new also and the hoses. I even added an extra heater core and plumbed it to the back for extra cooling capacity, so I should have plenty of radiator. I can have the heater on as well and by the time I get to the top of a good mountain climb, he is running hot. New 160 degree thermostat as well and new radiator cap. This thing has me flustered. It acts like no other overheat problem I have ever had before. I wonder if I am just not getting enough circulation and the water is boiling somewhere in the head or something. I need a way to check flow and I need to know about how much it should be.

 

[Trevor Jessie]

Are you sure it is air pressure and not a vacuum?

 

[jlaird]

Are you sure that radiator cap is correct for the type system?

 

[PAUL161]

Could be an air lock in the system somewhere. Even though it's new, the thermostat might not be opening fully. I had this happen once. Does the top hose get hot? If not, check the thermostat again. Does the water pump have the right gasket on it. Now I know this might sound crazy, but some thermostats can be put in upside down. If that's so, naturally it won't work but the heater will work depending where it gets it's supply from. These are just a few thoughts and who knows, one might be the problem. Otherwise and hopefully not, there might be a blockage in the block or head.

 

[regularman]

Are you sure it is air pressure and not a vacuum?

No its definitely pressure. It will nearly blow the plug out of the hole. I am thinking of trying the system with no pressure at all on it as a trial and see how it acts. I know it will heat up sooner with no pressure but it should just expand into the over flow and then draw back in when it cools.

 

[jlaird]

But only if the radiator and the radiator cap are designed for that.

 

[dklawson]

Kim, I know you tinker with gauges like I do (and you may have checked the gauge calibration)... but have you confirmed that "hot" really is "hot"? Have you checked the coolant with an IR thermometer or an immersion thermometer in the radiator header tank?

I can't offer suggestions about the air in the system.

As for the water pump, I think for high-flow and efficiency the pump to use is the GWP134 which has the large cast impeller.

 

[regularman]

Yeah DK I know exactly where boiling is on the guage. The interesting thing is the dissappearing water and the pressure. I need to put on an extra catch jug and see if the water is being forced out of the radiator into the overflow tank and past the cap. Now that its cooler weather I have to run it hard to get it to overheat. It only overheats when the water level in the radiator gets low, but where is the water going? I have a presssure tester and at 20 lbs on it for 10 minutes it held good, so no leaks.

 

[dklawson]

Did you perform your pressure test once the engine/coolant was hot or did you do the test on a cold engine?

 

[Trevor Jessie]

I understand that the system builds pressure as it gets hot. But, when it completely cools off why is there still pressure? It should have vacuum if anything... right?

 

[regularman]

I understand that the system builds pressure as it gets hot. But, when it completely cools off why is there still pressure? It should have vacuum if anything... right?

In a normal cooling sytem yes, there should be a vacuum that pulls water back in to refill the system. It is normall just thermal expansion that pushes the water out and then when it cools it draws it back in. What I have is pressure that stays long after the engine is cooled. What I am thinking is that I have reduced flow and the water is actually boiling in there and after it shuts off it continues to boil and build pressure and this forms a pocket of air that does not get re-absorbed by the water.

 

[Trevor Jessie]

The problem I see with your theory ... when water boils it creates steam (not air) when the steam cools it makes water.

If you have pressure in the system then I'm thinking there is still a head/head gasket issue.

 

[histerical]

I figure that if steam was present, the expansion would be greater than just hot water, and you would have even more vacuum when cool. In any case, I don't see how you can have pressure in the system after cooling down.
I was also going to suggest a head gasket leak. With the car running warm or hot, put your hand near, or hold a cloth over the exhaust and see if you are getting a lot of moisture. Or, do you see white ( water vapor) smoke ? If you are loosing coolant and don't see a leak, then you might be burning it. If you were burning a strong anti-freeze mix, I'd think you might even smell it.
If you have an overflow tank, only that cap should have a pressure relief spring. The one on the radiator should be a straight sealing type.
Bill

 

[dklawson]

If it's a head gasket leak into/out-of the cooling jacket, perhaps a leak-down test performed on a warm or hot engine would confirm that as the problem.

 

[regularman]

I see no fogging like when one is burning water. This is the wierdest one I have ever had. Full of water that engine settles in at a nice temp until the water goes somewhere and then it starts to heat up. I really don't think it is a head gasket. I have the die to check for that. Maybe another hot systme pressure test is what I need. My gut feeling is a flow restriction somewhere, because I could drive it easy on level ground for a long time and not have the problem in cool weather, its only when in stop and go that it starts to heat up. I need to rig up some hoses and flow some water through the system, this is nuts.

 

[JPSmit]

This is me thinking out loud.

1. you are loosing rad fluid.
2. you are overheating.

these two facts are likely related.

let's start with the fluid loss since that seems the most likely cause of the overheating.

it can only be leaving from a few places

1. head gasket. - seems unlikely based on your checks
2. water pump gasket - perhaps - permatex would solve.
3. hoses - theoretically would drip
4. freeze plugs - ?

Of these, 3 & 4 could drip under pressure but not when cold - maybe 2 as well though unlikely.

all of which makes me wonder whether you have a pinhole somewhere either in a hose or even a partly rusted freeze plug that only looses liquid at heat - and thus overheating.

thoughts

 

[regularman]

I have been thinking freeze plug myself. I never really gave them a hard look under pressure. I wonder If I could knock them out and replace them without pulling the motor. I am kind of curious to see if there is anything in there.

 

[Hap Waldrop]

If there's a breach in the system then a pressure check as suggested above will confirm that. Bum, borrow or buy a pressure checker and give it a look. If you pressure check and the leak is external then you'll see a drip, if it's internal it will show up in the oil.

A air pocket in these cars is always a possiblity, most racers put some sort of bleeder in the thremostat housing to bleed the system off there, you can also try running the engine for a monment with the radiator cap off and topping the collant up if needed, and then when confirmed full put the cap back on.

 

[regularman]

If there's a breach in the system then a pressure check as suggested above will confirm that. Bum, borrow or buy a pressure checker and give it a look. If you pressure check and the leak is external then you'll see a drip, if it's internal it will show up in the oil.

A air pocket in these cars is always a possiblity, most racers put some sort of bleeder in the thremostat housing to bleed the system off there, you can also try running the engine for a monment with the radiator cap off and topping the collant up if needed, and then when confirmed full put the cap back on.

I have a fairly nice pressure checker that I broke down and bought last year when I could not find a leak in the wife's car. It works good. I have never seen any evidence of water getting into the oil, no ugly whitish stuff on the dipstick. I have pressure checked it a few times and never seen any leak at all with 20 lbs on the system for a while. The water is going somewhere, I just don't know where. It is always the same thing after the car has cooled down to cold, the little tank is full and the radiator is about a quart low and there is pressure when I remove the plug from the radiator. It could be some compression getting into the system, I just can't figure it out.

 

[RonMacPherson]

Then next step is to check for combustion chamber leakage.

Two ways that I use. One is with a shop that has an exhaust "sniffer". Smog checking machine. Warm the car up, with the radiator cap removed and coolant appx 1 inch below the neck. With the engine running hold the probe over the coolant. If you get a reading of exhaust gases, you know the heads have to come off.

The other way is a cylinder leak down test with a warm engine. Again, remove the radiator cap. When you pressurize the leaking cylinder watch the coolant come out of the radiator.