Coolant loss at high RPMs

B

Bill Batson

Member
Hi Guys

I'm mostly a lurker - I do post post once in a while but have a situation I'd like some opinions on. I finished my Brookville bodied AV8 last year (after 12 years) and have put about 100 miles on it so far. Has a 1951 1BA engine bored .080, Bubba mechanical advance dizzy, Max 1 cam, .050 milled off the stock heads, single Holley 94 and has been running excellent. Block was boiled and cleaned and magnafluxed which showed no cracks. Plugs show a nice cream/brown color after a ten mile run.

Today I took a ride and on the way home ran it up harder in second gear and it suddenly shot coolant out from the radiator cap. Its an aftermarket Walker pressure radiator and I'm using Speedway pumps. Temps on both heads were running 160 - 170 with no fan on. As soon as I slowed down the coolant stopped escaping.

When I got home I removed the cap and started the engine. No bubbles at idle or up to say 2000 rpms but as I increased the rpms bubbles did start showing - stopped again as the rpms came down. I had torqued the heads three times to 45 lb ft as Ole Ron suggests. Does this sound like head gasket leak, pump cavitation, or could I have developed a crack even after magnafluxing. Since I first started it temps have never reached over 190 degrees. Also, checked the oil and it shows no signs of water - still is clean and fairly clear. Right now I am not running stats.

Any help would greatly be appreciated and I will post some picture soon. I used all old Ford parts that the local street rodders were discarding. Its basically a Bishop/Tardell build & I love it.

Much Obliged
Bill
 
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Doubt if it is an engine problem. Sounds like the radiator can't handle a very high flow rate. Pumps could be cavitating.
 
Remove the upper radiator hoses from the heads. Remove thermostats if you have them in there. Fill the engine with water up to the thermostat necks then remove the water pump belt. Crank the engine and look for bubbles in the water necks.
 
Ken/Alabama has a sure fire method of telling where the bubbles will be coming from. Magnetic particle inspections will show up cracks in places you can see but it won't help for the odd ball places. Pressure test of each side of the block will find any cracks that can't be found with MPI. Hopefully it's just a head gasket interface problem if it's pushing gasseous mix out of the water jackets.
 
im with flatjack9, I think the water is being pumped to the top of the radiator faster than it can flow to the bottom, and then being forced out the top
 
Hi Everyone, Wouldn't a modern exhaust gas tester, put near the radiator neck while it's puking, tell if they are exhaust gasses?
 
There was a guy here in town with a 35 Ford who had his engine rebuilt and when it was in the chassis he had the same problem. Bought one of those kits that supposedly checked for exhaust gas in the coolant. It showed positive. He was positive he hac a cracked block so he took the engine out and was going to get a different engine. He happened to call me and I said I would pressure test the block. Tested fine so I rebuilt the engine for him, put it in the test stand with his radiator and the damn thing puked water. I thought what did I miss? Tried all different tests - nothing. I had a radiator sitting around for my 36, put that on and that solved the problem. His was an aftermarket radiator and just would not handle the flow.
 
Thanks to everybody for the information. Flatjack may be on to the problem as I bought a 1932 repo radiator from Walker. It cools very well but is a much smaller radiator than my 51 Tudor has. The Speedway pumps are suppose to move a lot of water - more than the stock ones so I may be fighting the pumps against the radiator size. I can not smell any exhaust from the bubbles - don't know if that means anything.

It will cruise all day at 60 - 65 mph with no problem. It was just when I stood on it hard in second up to about 50. I retorked the heads and the bolts did pull up a bit.
 
I kept blowing head gaskets in my 8BA rebuild until I re-torqued cold after every heat cycle until there was no more movement in the bolts. This took a lot more than three re-torques. Symptoms each time were puking water. By contrast, years ago I never once re-torqued my new 81A motor and had no problems ...
 
Bill, I don't know anything about your new radiator but can tell you how stock radiators act. First of all most of these systems were designed for 22 quarts of
coolant. Less coolant and they run hotter. The radiators should be filled up into the filler neck. The problem is 144 tubes are 24 or more inches long, have a little dirt in
them and restrict the flow of coolant through them. If you could dump a volume of
into the radiator with the bottom hoses removed the water will back up and slowly
pass through the tubes. More water than that is being pushed in to the tubes by the
two pumps, it can't free flow through the tubes, backs up in the top tank and on early
year cars with the over flow from the top the excess coolant go's out the over flow.
On later years with a WORKING 4 lb pressure cap the cap causes the coolant to be FORCED through the tubes. No coolant is lost and better cooling results from having
more coolant in the system and more coolant flowing through the engine and radiator.
Skip Makes a 3 lb pressure valve that is installed on the bottom of the radiator over
flow tubes on radiators that are not set up for a pressure cap. Don't use the 3 lb valve
on radiators that will accept a pressure cap. I said WORKING pressure cap above meaning a cap that the rubber spring loaded bottom end hits and seats on the washer like seat about 7/8" down at the bottom of the filler neck. I find for some reason MOST
do not hit the bottom before the top of the cap hits the top of the filler neck. This leaves the bottom rubber loosely touching the washer seat. I install a red rubber washer on the bottom seat made from the 1/8" material found in hardware stores. With the slightest back pressure coolant is pushed out the over flow. This pressure can come from the restriction of the tubes, water pressure if the temperature is above 210 or from a compression leak. Running with no fan is going to bring the temperature up above 210 at low speeds and idle. Going down the road the faster you go the better the cooling below 75 MPH. First do the test described above, remove fan belt and upper hoses, fill heads or pumps up to the top with water and run the engine at idle 2 or 3 minutes looking for bubbles on both sides. If you see bubbles you have a compression leak, if slight install a bottle of heavy duty Barr's stop leak and it should solve the problem. I find all most all old Fords have some slight leak and add a bottle to every engine and never have a problem after that. A slight leak will show a small amount of black water out the exhaust at start up and usually go's away as the engine warms. After the Barr's treatment I very seldom see water out the exhaust. G.M.
 
Thanks 49r & George.

49r - I will be retorquing the heads a couple more times as I believe your right that these new gaskets take more than three times to get them set. I also increased the torque to 50 lb ft to try for the best seal.

George - I have a Walker radiator which should be one of the best aftermarket ones available and obtained a Model A/ 32 style. Its a three row 13 lb pressure radiator physically the size of a of a Model A radiator.

I have an pull electric fan (no shroud) on the radiator but have never turned it on as the temps seldom get over 180 degrees - I live in a rural area and spend little time in traffic. Although even after idling 20 min or so while setting timing and adjusting the carb etc. it stays cool. I am seriously considering removing the fan.

I believe you are correct that it is either the radiator is too small (too much resistance) to take the flow of coolant at higher rpms or I have a compression leak. When this happened I was running about 50 in second (3:78 rear end - 7.00 by 15 tires) and the water escaped from under the cap in a rush not thru the overflow tube. Sprayed the windshield, cowl, firewall, etc. Now did I have a senior moment and not have the cap completely tightened? Very well could have but I don't think so.

I did check the cap (provided with the radiator by Walker) and mating in the filler neck and it seems good contact is being made and the spring is applying pressure when the cap is pushed down and turned. I could try using a red rubber washer as you mentioned to increase the seal - that would be an easy alteration.

As per your advice I will be checking for leaks using Ken/Alabama's method but I believe from what everyone has said is the item you first described. The flow is too much for the radiator size at high out put. I know it doesn't mean much but looking thru the filler neck with the engine idling or running 1500 or so not one bubble can be seen. Above 2000 rpm the water start jumping around and bubbles form

Thanks very much for your help.

It makes me feel young again to drive her.

Bill
 
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Bill Batson said:
Thanks 49r & George.

49r - I will be retorquing the heads a couple more times as I believe your right that these new gaskets take more than three times to get them set. I also increased the torque to 50 lb ft to try for the best seal.

George - I have a Walker radiator which should be one of the best aftermarket ones available and obtained a Model A/ 32 style. Its a three row 13 lb pressure radiator physically the size of a of a Model A radiator.

I have an pull electric fan (no shroud) on the radiator but have never turned it on as the temps seldom get over 180 degrees - I live in a rural area and spend little time in traffic. Although even after idling 20 min or so while setting timing and adjusting the carb etc. it stays cool. I am seriously considering removing the fan.

I believe you are correct that it is either the radiator is too small (too much resistance) to take the flow of coolant at higher rpms or I have a compression leak. When this happened I was running about 50 in second (3:78 rear end - 7.00 by 15 tires) and the water escaped from under the cap in a rush not thru the overflow tube. Sprayed the windshield, cowl, firewall, etc. Now did I have a senior moment and not have the cap completely tightened? Very well could have but I don't think so.

I did check the cap (provided with the radiator by Walker) and mating in the filler neck and it seems good contact is being made and the spring is applying pressure when the cap is pushed down and turned. I could try using a red rubber washer as you mentioned to increase the seal - that would be an easy alteration.

As per your advice I will be checking for leaks using Ken/Alabama's method but I believe from what everyone has said is the item you first described. The flow is too much for the radiator size at high out put. I know it doesn't mean much but looking thru the filler neck with the engine idling or running 1500 or so not one bubble can be seen. Above 2000 rpm the water start jumping around and bubbles form

Thanks very much for your help.

It makes me feel young again to drive her.

Bill
Click to expand...

You can't tell from looking down in the radiator if there are bubbles, it has to be filled up until it runs out the over flow in the filler neck. The sure way is with the belt and top hoses removed. The radiator isn't to small or it wouldn't be running as cool as it is. I think you tightened the head bolts enough times. Try the Barr's. A small or clogged radiator will cause over heating, you don't have that problem and the water is flowing through the engine and radiator or it would be running hot. Your problem is with the cap. If it only did it once I would say you didn't tighten the cap. I would also replace the cap with a 4 to 6 lb cap, all you need is a 4 lb one. Pressure doesn't come into play AT ALL BELOW 210 degrees, to high of a pressure cap doesn't give you any protection from high pressures in the system. If a hose breaks with 15 lb pressure and your near it you will get burnt. You don't want the red rubber, your cap is working. Putting the rubber down on the seat with a working pressure cap that is already down on the bottom seat will increase the pressure the cap releases at. The pressure cap is also a pressure relief valve to release pressure above it's 4 lb rating. G.M.
 
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