The Triumph Dolomite Club - Discussion Forum

my overheating Sprint.

For more months than i can remember now i have been trying to get my Sprint running following body work and then curing overheating. A previous thread showed the cam bolts finally sheared which resulted in a full strip down. I got a good block from Tinweevil and had the head tested and thought all would be well. Last weekend i finally got it running again.

I had to play about with the twin 45's and the distributor to get it to idle and the carbs were not set using any equipment for balance/mixture at this stage. The bypass tube also has slight leak and the exhaust manifold was blowing a bit on the head even though it was torqued down.

Not long after running it the head started to get very hot again ( i shut it off at 95 deg) . The rad pipes were not very hot though so it would seem that there as no circulation. The rad took the exact amount in the book for coolant and it was filled with the heater on hot very slowly.

The water pump has been rebuilt. Recored rad , new pipes , new timing gear , new head gasket, head pressure tested.

I have just pulled the head off again to sort the exhaust manifold as i will get it skimmed so that it seal properly. The bypass tube should be an easy fix but what can i do next to sort the overheating.

I pushed on the impellor to check it was not rotating freely and this was ok. I used the correct gasket thickness as well.
Could the exhaust manifold or the leak from the bypass tube cause overheating this quickly , i would suggest not .

Massive airlock , could be but the coolant amount was spot on.

I have read differing opinions on electric pumps but i am tempted to try this although that would assume the current pump is no good as it is not likely to fix any other causes.

Any help or suggestions would be welcome in stopping this car being off the road for it's 9th year.

I assume you've changed the thermostat and rad cap?

Hi Mike, Just as a try out would you like to borrow the rad currently out of CWL ? It is known good.
Just in case there is something odd with the carb; jetting would you also like the loan of the original SU carbs ?
Somewhere I also have a good cylinder head off DHO .
It might prove something.

This just has to be fixable !

Cheers for now,
Tony.

frustrating for you Mike, sad business when something isn't going right. At least you have realised there is a problem and haven't damaged the engine.

The rad pipes were not very hot though so it would seem that there as no circulation.

does the top hose from the thermostat housing to the radiator get hot ? if it isn't then a thermostat isn't opening. Try removing the thermostat as a trial. Run the engine nd see if the pipes now get hot.

with the thermostat removed, remove the thermostat cover and see if you can see the water pump actually working, pushing water into the big hose. Obviously do this when the engine is cold. that should reassure you that the pump is working.

2 simple-ish things to try that should eliminate the thermostat and the water pump as the cause of the problem.

good luck

stu

It was a brand new thermostat, overflow bottle and cap as well. Thanks for the offer Tony of the parts. If i was running untested parts or old parts i would take you up on the offer but the rad was re-cored by Feltham Rads and the head has been tested so i am confident there are no major issues with them. I may end up eating my words but i would like to eliminate all else before fitting trial parts. Carbs are no doubt in need of setting up but have run ok before and i would be very suprised if they gave this sort of overheating in such a short time from start up whilst idling on the drive..

I think i will have to set it all up again once the manifold is skimmed and then make sure the bypass hose seals ok and run it again taking note of what warms up first and what does not. Still tempted to go the elctric pump route but no guarantees there either.

Hello, you cannot run a sprint or 1850 without thermostat. It has to be a double working stat. When the engine is getting on temp, the lower part is closing the bypass. When running without stat the coolant flows through the bypass and never through the radiator. When having the wrong type of stat, a single working, it will open the main flow to the radiator but the the bypass isn't closed and the coolant will still run internally. The rad hoses will not get warm because there's no flow to the rad and the engine is getting too hot very soon.

Do you have the right stat in your car?

Jeroen

Jeroen

Yes i have the right thermostat with the plastic part in the rim. This is why i am getting so frustrated , i have done so many things , bought so many parts and still i can't get it running at the right temperature. I am determined to crack it though as i am too far down the line now.

Hello, that's not what i mean.

Not this one: but this one with the valve at the bottom. Jeroen

Got one of those as well. Keep the suggestions coming.

thanks Jeroen, my poor communication. I was suggesting that with the thermostat out, there would be some heating of the top hose and you could observe the rush of water through the thermostat housing. Sorry, I should have made it clear I wasn't suggesting running without a thermostat during normal driving.

stu

Never assume new parts to be fault free!

Now more than ever do not trust repro parts as most are cobbled up in China and the originals were bad enough but the repro

Just for something else to try, if you have the thermostat housing off , try poking a bit of fuse wire through the air bleed hole in the casting from the smaller diameter radiator hose side. ( Remove the hose first ). If that hose is full of water its probably O.K. though.
HTH,
Tony.

Also you need to be cpmpletely sure your intsrumentation is right.

I fitted a new sender to a car last year...and it was indicating too hot. I swapped it for an original one from an old TR7 manifold and hey presto...correct reading again.

Jonners

Yep , same issues some time ago, all new stuff but still reading hot. Changed sender unit(it was a brand new one!) & all was well. Make sure it is actually getting really hot. Capillary temp gauges are supposed to be the best/most accurate, not affected by voltage fluctuations etc. (Having said that though the capillary one in my car goes up by about 8-10 degrees everytime I brake!). I once even fitted a secondary gauge in the plate at the very back of the head , just to be sure. Do you know anyone with a laser temp gauge, not great I know but at least it will give a good indication if the motor is really getting too hot? and it does not involve a lot of unnecessary work/changes?? I have also seen recon'd radiators coming back blocked??
Hope this helps & don't give up !!