The Triumph Dolomite Club - Discussion Forum

I have the head off my Sprint engine because of a boiling over cooling system, I suspected a head gasket. Alas I can't find any evidence of that. I thought I had found the problem when I checked for flatness with a spirit level and the head didn't seem flat. However I ordered engineers straight edge and checked with a feeler gauge.

There is absolutely no evidence of warping and the head looks fine, unless I have done it incorrectly. The block surface is also flat. I though there might be a crack somewhere but searching with a UV torch (I put UV dye in the cooling system), reveals no issues. I would assume the dye would have picked them up.

So I am going to refit with a payen gasket and not head bolts. I did wonder whether it would be worth skimming the inlet ports to get a better seal on the manifold? Coolant tends to leak in that area.

Why did you suspect the head gasket?

Check your water pump hasn’t stripped the teeth off the gears or the impeller isn’t spinning on the shaft....were the engine running, you could check this by seeing if the bottom hose gets warm, or not.

Did you notice the coolant level going down at all before the engine boiled? Did you try another pressure cap?

If you have an issue with the head gasket, such as combustion gases getting into a coolant channel, I would expect to see traces on the head, block and certainly gasket. Also that would tend to push quite a lot of coolant out when it boiled.

If you are replacing with a new head gasket, when I have suspected an issue, I have used a light spray of a copper (sold in NZ as Copper Gasket Spray) on both sides and then been very careful in ensuring torquing down is done in the correct order, in increments and then retorqued after 500 and 1500 miles when stone cold.

It is a good idea to use Hylomar around both sides of the inlet gasket where the water passage is.

Also while the inlet manifold is off, I would suggest take a good look into the water pump and even if all appears well, reset the clearance. Test the thermostat is opening as it should while everything is apart. If all else fails you could try putting dye in the coolant again so any leaks can be more easily seen.

Geoff

I will have a look at the coolant pump, because it shouldn't be difficult to get at. I have already checked the thermostat and everything was OK. I suspected the head gasket because I could see bubbles in the coolant. Already changed the cap and the coolant bottle.

The inlet manifold is a joke, I didn't need the feeler gauges to see it wasn't flat. I could use the engineers edge like a seesaw, so I am definitely getting that skimmed.

Was it overheating or just bubbling in the expansion bottle?

Jeroen

soe8m wrote: ↑Thu Mar 12, 2020 9:28 pm Was it overheating or just bubbling in the expansion bottle?

Jeroen

Bubbling in the expansion bottle and coolant pouring out of the overflow. I didn't give it a chance to overheat.

When it bubbled without overheating you don't have to check the waterpump etc.

Coolant bubbling in the expansion bottle means too much pressure in the cooling system or too less.

Too much can be caused by a leaky head gasket having combustion gasses pressed into a waterway. This cause can be tested easily but that had to be done before the head was off and with the engine running. What you can do now is to check surfaces and have the head crack tested.

Too less can be caused by a faulty pressure cap releasing coolant too early and having air in the system what will cause the bubbling. New caps are crap and NOS caps on plastic tanks can have issue's also as plastic tanks can stretch a little where the cap sits. This can be tested by pressurising the bottle and see at what pressure it blows off. Too early you can fit a stronger cap or add washers under the springs to adjust. I use 15 or 18lbs caps on dolomites and these work fine. The coolingsystem can handle the extra pressure easily and keeps the coolant inside when the temp rises incidentally by some reason.

To diagnose it's also good to know when the bubbling starts. When the engine is cold and it starts bubbling immediately it's very likely too much pressure by a leaky gasket. When it starts at normal operating temp the cap or tank is more probably the cause.

In some cases a wrong type thermostat can cause the bubbling but I think that is not the cause here as you should read a higher temp first before the bubbling starts.

Jeroen