The Triumph Dolomite Club - Discussion Forum

Hello All, I'd appreciate your ideas of what's happening to my Sprint which I just acquired. The car is very lumpy on idle but positively flies once its over 2000rpm. While driving it around, I heard a piercing high pitch sound, coming from front of the engine. The temp was showing 3/4 and rising but the radiator top was cool!! No pressure in the expansion tank, I opened it without any rush of air. The thermostat housing has three hoses leading out of it - all cool or luke warm to the touch while the housing itself was very hot.

Is the high pitched sound that of a dead water pump?

The first thing to do is let it cool and check the water level, not in the expansion bottle, but via the brass plug in the thermostat housing.
besides a low water level, the next thing I suspect, is what happened to Mahesh's Sprint recently. That is a blockage in the small pipe in the thermostat housing that leads to the expansion bottle. Finally, it is more than possible that the thermostat itself is faulty. I suspect the scream you heard was high pressure steam with nowhere to go!
Lumpy idle could have many causes, but first check is that the choke is clearing properly at the carbs. this would give you an artificially rich mixture that makes it pull like a train at high revs but run rough lower down the range. If that's OK, it may just be set up too rich which would have similar results. But check the choke mechanism first to avoid embarrassment later!

Steve

Yes now that you mention it, it does sound like a kettle going on at full blast!

The other possible sources of a scream from the front of the engine are a seized torque converter in the fan and the belt slipping. But a fan belt slipping is a fairly common sound, and I assume you'd probably recognize it.

A stuck torque converter makes a truly horrible noise, until the fan unit flies off through the rad. But it's possible to hear that when you just rev the engine. If it is that, it often goes quieter for lashings of WD40, but only for a while. Fan belt slipping noise will also go away for a bit for a spray, as well.

If it's the torque unit, that's bad news - they aren't cheap. Can be cheaper to fit an electric fan, though that's not necessarily free of problems if there are other cooling system issues like, by the sound of it, a blocked hose or stuck thermostat. I'm still not happy with the way my set-up behaves driving in slow traffic in hot weather - though I've yet to test it properly since replacing the pump. I've a suspicion I need either a better rad or a bigger fan and alternator to make it work properly.

Graham

Remove the alternator drive belt and then start the engine,
if the noise has gone then you know it is either the alternator or the viscous coupling assembly.
Then it is a case of elimination to find the cause.

If the noise is still there then it is going to be expensive....


The overheating may be due to a stuck closed thermostat as Steve suggested.
Alternatively, it may be failed water pump (where the pump turns but the impeller does not or a stripped
pump drive skew gear).
Check the thermostat first…..




Ian.

Thank you all. Having the 'full' Sprint engine (the V8 in my Stag), I'm used to expensive bills . I'm much inclined to think its escaping steam from somewhere. The car was low on water so i'll be checking that first. Having the expansion bottle half full of water misled me into not checking the water level

The important thing here is that though the engine was stinking hot and low on water, you had half an expansion tank full of COLD water and NO pressure under the cap when it should have been venting by rights (hence the screaming steam). It's not hard to take the pipe that leads to the expansion bottle off the stat housing and have a poke up the metal tube with a bit of wire or a small drill bit twisted with your fingers to make sure there is no blockage in it. Take care though as this tiny hose neck is inordinately fragile when old!

Steve

On mine, the thermostat housing small pipe was blocked at the internal orifice as Steve mentioned.

When pressurised the coolant would come out of the slot underneath the water pump.

I had the water pump out a total of 5 times (& three rebuilds), not once after cleaning out the stat housing, I hope yours has the same easy fix, worth checking first.

Will buy the blue stuff and will replace all the coolant once I'm at it.
Silly question-I can understand 2 pipes going to the rad top and expansion bottle respectively, but why have a third pipe also going to the rad top, on the opposite side?

The RH top radiator spout is a vent.
Without it, creating an airlock within the radiator is likely.




Ian.

This thread highlights the reason I did away with the standard expansion bottle, and replaced it with a modern expansion tank from a Volkswagon, as the modern tank has a lower drain which I piped in to the return to engine bottom hose. This also means that a top up goes into the engine and remove the chance of air locks. I also blocked off the top right hand 1inch hose between rad and thermos housing to ensure all water goes through the rad.
Was I right? However with the car flat out going down Silverstone circuit the cars temperature was actually going down!!

Hope you have cured this problem.