Froggy dolly 2 is boring me !

[dololo]

Hi , those who read my post froggy dolly 2(my french sprint ), already kow i am fighting since last summer to solve all my issues .
After a complete engine rebuilt , at the first rally , always bubbles in the coolant tank , and coolant consumption.
we took off the head and checked the head gasket : it seemed ok
we did a pressure test on the head : the problem was a leak in the first inlet port
fitted a new tested head+ an new improved radiator , and an new checked coolant tank cap , and still the same problem , the coolant level increases in the tank , until it overflow , and the cap over the thermostat housing is full of gas , after 5-7 miles .
The car is not overheating .
I don't know where to look to solve my problem .

[triumphdolomiteuk]

Check the coolant overflow tank is sealing with the new cap. I had a similar problem about a hundred years ago with my car.

[dololo]

Thanks fior your suggestion , i tested it with a bycicle pump ; it's opening at 15 psi .

[Carledo]

Is coolant getting into the oil in the sump?

Steve

[soe8m]

You can do a co test. There are test kits that detect exhaust gasses in the cooling system. When the bubbles contain exhaust gasses it is defenately a non sealing headgasket or another reason a cilinder is in contact to the cooling system. Do you do the spanninering yourself? Do you use the correct tightening sequence?

Jeroen.

[dololo]

Hello ,
tightening sequence
-first the line on inlet side , the center one , then the first right one , then the first left one and the extremities
-second the exhaust side , the same way

torque in 3 times
-first 2.5
-second 5
-third 7.6 kg/m

Jeroen , i will buy a Co test , this will help me identify what the bubbles are made of

[GrahamFountain]

I was told by a Sprint owner (admittedly talking about a competition engine) that he'd once had to have the top of the block skimmed to get the head to seal. He said that the studs and bolts had, probably, been over torqued, and had strained the casting around the holes.

I have no idea if his theory was right or even possible. But he said that skimming the block fixed the problem where neither skimming the head nor a new one had.

Graham

[dololo]

Is coolant getting into the oil in the sump?

Steve

No , no coolant into the oil
just gas in the bottle and thermostat housing empty .
I did a co test this afternoon , and the test liquid go from blue to green ...

[dololo]

still with my problem .
No CO in the expansion bottle now
cap + bottle tested , opening at 12 PSI
but the coolant level always increase , in the bottle


I will try this afternoon to suppress the thermostat

i will maybe try to modify the bottle into an expansion tank , by :
- drilling a hole near the top of the bottle to connect the hose to thermostat housing
- connecting the bottom of the bottle to the bottom hose of the radiator

see picture below

Doing this way , i think that air pressure will "push" the coollant into hoses instead of making an air lock in the thermostat housing
Am i right ? Did anybody already tried this ?

[cleverusername]

Since your's is a race car, are you using an alternative or upgraded rad? I ask because I had similar problems using a Saab rad, which went away when I switched to a standard Sprint rad. Though I have no idea why that should have made any difference.

[Carledo]

Since your's is a race car, are you using an alternative or upgraded rad? I ask because I had similar problems using a Saab rad, which went away when I switched to a standard Sprint rad. Though I have no idea why that should have made any difference.

I can't understand why the Saab rad should cause you grief either, the Saab rad has necks in effectively all the same places as a Sprint one!

To the OP, I asked about coolant in the oil to see if I needed to suspect a cracked block, a fault I have met 2 or 3 times in recent years. It would appear this is not the case with your car as an internally cracked block invariably deposits water in the oil.

Steve

[TrustNo1]

are you bleeding the system with the heater blower on hot and topping up via the thermostat?

[dololo]

radiator has been upgraded , but is still a sprint one .i had the same problem with the original radiator .

i bleed with heater blower on, first feeding the bottle to the right level, then engine run 3 minutes , and topping up the thermostat housing after .

[dololo]

tried a new bleeding this afternoon .
bottle level expanses until overflow (it takes approx 15 miles drive)
but what surprises me is that when cold , the level doesnt decrease .
Does it mean that air is not allowed to enter trhrough the bottle cap when temperature (and so pressure) decrease ?

[Jod Clark]

tried a new bleeding this afternoon .
bottle level expanses until overflow (it takes approx 15 miles drive)
but what surprises me is that when cold , the level doesnt decrease .
Does it mean that air is not allowed to enter trhrough the bottle cap when temperature (and so pressure) decrease ?

If the level in the expansion tank rises but doesn't get drawn back into the system as the engine cools then air is getting in from elsewhere. A full cooling system pressure test is needed to find it.