Heat exchanger problems yet again!

Just an afterthought, if I have overfilled with coolant and the new cap has some kind of anti corrosion spray on it that might be reddish...............Could it be that simple???

Edit: Look at the color of that spring!

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This how they treat them before packaging.

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Carmel2 said:
It started last year. I was running the engine on quite low revs (1500-1800rpm) because we have added a lot of weight to the boat: an inbuilt 4.5kw generator, watermaker, 100 metres of 10ml chain, a gantry with 4 panels, 100 metres floating line, kedge anchor, plus we have 70 kg of rib and outboard strung up. So less revs, less stress. Then we happened to be talking to an engineer who said we should be running it at 2500rpm, so we did. Soon after we started seeing coolant coming out the overflow so did the test that Vyv mentions and no problem. We found if we ran the engine at very low revs it didn't leak. Once back in port for the winter, the engineer we use came to see, took the pressure cap off and ran it up to temperature, and the coolant was bubbling, so he diagnosed a blown head gasket. It was taken apart and sent to Volvo in Athens to be milled flat and cleaned out. The heat exchanger was pressure tested to 1 bar, not dye tested. The injectors were cleaned, all new gaskets and rubber end caps, exhaust elbow, new calorifier, with all new pipe work and fittings. So we set off this year and had no worries until the last but one journey when the bright green coolant leaked from the overflow. So we sourced a new cap as that was the only thing that hadn't been replaced. We went off again and that was when the purple liquid started coming out of the overflow, so back to port. Below is a pic of the cap I took off this morning, you can see the red/purple on the bit where the cap sits and in the coolant. In the engine bay this morning the liquid has not separated, it's still the same as the photo. If it was the gear oil, or indeed any oil, I would have thought it would have separated.

This morning I tried get the bolt out of the gear box that acts as a dipstick. You can undo it to the point you can do it with your fingers and you feel it's loose, but go a quarter turn and it tightens. So, back with the socket wrench and 3 or 4 more turns and it's loose again but the same thing happens and after 50 or 60 turns it still doesn't come off, just the same thing over and over again. It tightens up ok, is it threaded?


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Hmmm ... Ive seen it before when a head gasket has been diagnosed and it turns out to be a crack in a head (same symptoms)so personally i ALWAYS get the heads pressure tested before anything gets done to them, or what happens is you spend a fortune getting the head skimmed and valves cut/ recessed etc and then only to find the same symptoms when you bolt it all back together, then you end up asking yourself have you torqued it properly ...blah blah blah... im not saying thats whats happened but bear it in mind.....the fact you have worked this engine since the repair suggests it shouldnt have any cracks unless new.

the colour thing makes little sense to me or anyone else it would seem - I have seen an antifreeze in a shade of pink that looks almost pearlescent , very close in colour to what you have - but it would / should have mixed with the green stuff and not be visible at all

did you try running the engine today with the cap off for a bit as a few of us suggested ?
if so what was the result?
that over flow pipe in the picture does it go to a plastic expansion bottle or into the bilge ?

heres my take on it....go back to basics.... disconnect and BYPASS ALL AND ANY coolers and colorifiers, then run it again and see what happens, at least then you will know IF the engine is sound or has a fault, if the engine is good , start adding stuff back into the system one at a time

I like the description of the boat , it sounds so similar to us, we are over loaded with similar kit, listen to the engine note, find its RPM "happy spot" we can make 6.5 under engine and within the RPM range, but I dont like the sounds or the increased vibration in my minds eye I can see whats happening under the saloon floor - drop back to 5.5 and it sounds so much happier - most engines are the same, find the sweet spot

as viv said the coolant is under pressure (look to bottom of rad cap) so the coolant would (should) go into the gearbox if you had a gearbox cooler problem, as for the bolt ....you arent having much luck are you , im assuming its a standard threaded bolt if so ..lefty loosey.. righty tighty if that doesnt work you have a thread issue, may even find its been helicoiled before if its doing what you describe... (voice of doom)
 
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Volvo have told me that they cover the inside of the cap and spring in soluble pink marker paint which explains the colour. I have just run the engine for an hour at 1250rpm, (any more and the coolant jumps around so much it spills.) When the coolant expanded it came out of the overflow pipe a lovely green, no plastic expansion bottle, straight into the bay, and after an hour no bubbles.
 
Did the calorifier contents get hot? If so you can eliminate any ideas of airlocks in the loop or coil. You just might have an air leak on the suction side of the circulating pump but I suspect that this would not introduce air one the coolant was at pressure.
 
vyv_cox said:
Did the calorifier contents get hot? If so you can eliminate any ideas of airlocks in the loop or coil. You just might have an air leak on the suction side of the circulating pump but I suspect that this would not introduce air one the coolant was at pressure.
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Yes it did get hot, and I had turned it off last night just in case it needed to be cold to do work on.
 
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