62 replies to this topic

[TheFabMini]

One thing which did seem odd (I’ve never had an engine overheat before) was when waiting for the car to cool down, the temperature gauge got to about 80 degrees and I decided to go and open the radiator cap to release the pressure and top up the coolant.
But there was no pressure at all... I’m guessing the steam lets out lots but I would have assumed it would still be under pressure???
Would this help towards the bad cap theory?

[viz139]

Should be pressure.

If the head gasket was gone the pressure could be coming from the engine and would also cause coolant loss. need a compression test.

The fact that it is happening at low speeds suggest a big problem.

[CityEPete]

Is it piped up correctly taking into account there's no heater?

[TheFabMini]

Is it piped up correctly taking into account there's no heater?

Heater valve replace with a take off pipe, going back to the bottom hose. So effectively the same plumbing just without a matrix in the middle

[TheFabMini]

Should be pressure.
If the head gasket was gone the pressure could be coming from the engine and would also cause coolant loss. need a compression test.
The fact that it is happening at low speeds suggest a big problem.

This was my first drive after replacing the head gasket.. my compression tester got lost when I moved house so I’ll have to borrow/buy a new one

[CityEPete]

What did the water galleries look like when the head was off?

[TheFabMini]

What did the water galleries look like when the head was off?

To be honest I didn’t pay much attention... looking back at a photo I took they look as expected.. not blocked up.
When flushing the system and rad there seemed to be lots of copper/something shiney metal shavings in the water... almost like glitter

[gazza82]

Is the water pump turning easily? Wondering if it binding and rubbing. That may explain the overheating

[Pete - W.Sussex]

The copper/shiney metal shavings sounds like residue from that radweld stuff that is supposed to fix head gasket leaks etc.

[Spider]

Another possibility is a cracked head.

[mini13]

could be a rad cap issue, its worth replacing as a matter of course.

 

obviosly pressure will build in the system with heat, if its got hot enough that its chucked coolant out then when it cools a bit it could end up with no pressure, as the larger qty of air in the sustem  will contract more than when it had less air (more water) ... if that makes sense, also the green over flow pipe you can stick into a can, and when it cools then sustem should try to suck back in coolant that its chucked out when hot, somthing like a coke or beer can will do.

 

obviously water will boil at 100deg (ish depending on aditives) which you can easily see on a mini engine, the rad cap presurizes the system to about 12-15psi bushing the boiling point up to aroound 115-120 degrees ish, but once presure releases then boiling point drops and you get boiling.... so if the caps suspect!!

 

Also, how much air gap are you leaving, you need a good air gaip at the top, normally somthing like 1/3-1/3 full header tank.

 

 

 

 

One thing which did seem odd (I’ve never had an engine overheat before) was when waiting for the car to cool down, the temperature gauge got to about 80 degrees and I decided to go and open the radiator cap to release the pressure and top up the coolant.
But there was no pressure at all... I’m guessing the steam lets out lots but I would have assumed it would still be under pressure???
Would this help towards the bad cap theory?

[Clubby77]

Hi there,

What i would do to narrow it down:

- Are you really overheating or is it the gauge. If you have no other possibility of measuring you could probably boil the Sender if you give it an earth wire. and compare temperatures.

- Leakage Check (Pressurize the System with a pump) Cooling system ok? If it cant build up pressure it won't cool as well.

- Compression Check or even better a "pressure drop test" -> Head/Gasket ok?

- If you have one of those Laser-temperature-Gauges (missing the Vocabulary there) check the temperature drop between top and bottom.

(I will need to look up what a acceptable result was)  This will tell you if your radiator is fine.

 

Problems i had before: 

1. Gauge told me engine was overheating: 

Voltage regulator was broken. Check if you have 10ish Volt @ the Gauge when running

 

2. wrong or broken Radiator Cap could be an issue 

If the System is really not leaking there should be pressure at the cap, beware there is a long and a short neck Cap.

 

3. Boil the thermostat in water and measure the temperature at which it opens. I had a broken thermostat out of the box before. 

 

Edit: sorry i overread the part with the mechanical Temperature Gauge

 

The shiny flakes in your coolant are probably only rust particles. 

G Jan

Edited by Clubby77, 04 June 2019 - 12:29 PM.

[pete l]

He says he's getting steam, so it is genuinely overheating.

 

Get the cooling system pressure tested, I reckon it is not holding pressure.

[TheFabMini]

Thanks all for your replies!
A new fletcher alloy radiator just turned up, last night I disconnected the pipe from where the heater valve would be (I have a straight take off pipe) and the return on the bottom hose.. connected up my hose pipe and let it flush through for about 10 minutes from both ends...
I briefly started the engine whilst doing this to ensure that anything lodged might have been moved around..

It’s currently pouring with rain in Norfolk so won’t be able to fit the new rad tonight but should be dry tomorrow!
Also my new compression tester turned up today so might be able to go out and get some figures from that in a bit..

So at this point once the radiators on I’ll have!

New silicone bottom, top and heater hoses
Water pump new last year (approx 300 miles use)
New thermostat
New fan belt
New fletcher alloy radiator
New head gasket


So... if it still gets hot I give up and will find a new engine and move all my new parts across haha

Edited by ChrisRuffell, 04 June 2019 - 04:27 PM.

[Mikey205]

Don’t discount the block being full of silt and crud. I’ve just cleaned out all the block on mine and it was full of lots of nasties.
Remove the thermostat housing and water pump and have a good look around the liners, mine were full of corrosion.
I ended up just scraping it out and using compressed air to blow it out of the block.

A compression test won’t tell you anything so I wouldn’t waste your time. You ideally want a leak down test or a headgasket check running on it. I would suspect that your rad cap is about done for though as it should hold pressure for a good while after you stop the engine.

Oh, and it’s sunny as anything in Portugal while I’m writing this on my balcony........ Sorry, couldn’t resist......