27 replies to this topic

[JCmini]

Hi again. 

998cc automatic 1986 A+ 

Went for a long drive from Gatwick to Brighton around 65mph (top speed). Lost about half lire of water out of radiator cap and the same coming back up to Gatwick.  The temp was about 3/4 up. And at one point touched the red going up a really steep hill.

 

So thought I would upgrade the coolant system. Before I take the pump off just need second opinion. Do think its still good working order or time to change. I've read about rusty impellers. Will it be really obvious? 

 

And finally what the latest water pump people tend to fit or should I just get a direct standard replacement if I need one cheers. 

 

If the water pump is fine then I'm going to fit a external fan on the other side of the radiator like the one Ed China fitted onto the moke on wheeler dealers years ago. 

 

 

 

cheers

 

 

[nicklouse]

I would be investing my time and money if finding out why it is losing water. the cooling system as standard will manage way more that you are describing so something is not right.

 

is the cap correct?

is there loads of deposits/rust in the system?

 

pump condition can be checked by (when cold) popping the rad cap off and revving the engine while looking at the water level. the level should drop momentarily as the engine is revved as the pump sucks water out of the rad. if it does then the first thing I would do is get some cleaner through the system and get the water system clean.

[DeadSquare]

Unlikely to be the head gasket, as Gatwick to Brighton is about 30 miles and you only lost a pint, so I'd look for a leak.

 

  With the hoses blocked off and attached to the rad, hold them under water and gently pressurise it all with a tyre pump through a scrap chopped off tubeless tyre valve pushed into the heater return, and watch for bubbles.

Edited by DeadSquare, 17 September 2018 - 10:53 AM.

[Twincam]

Have you got the correct radiator cap fitted? If not it could be letting by when the pressure rises (if it's got a weaker spring)

[JCmini]

Well water is definitely coming from the over flow in the cap. I made my own expansion tank (plastic drink bottle) so I could see how much liquid is leaking.

 

I originally has a 7lbs cap when I bought the car. Then I found a 15lbs cap in the box of spares that came with the car. 

Is it likely both caps have had it?

[gazza82]

Possibly or the 15lb one you fitted was shorter and designed for a different neck.

[Spider]

Originally, it would have had a 13 lb Cap.

 

These sort of issues can always take a bit to nail down, but given your description, one place I would be looking is a rusted cooling jacket.

 

When the car gets hot, does it take a long while to cool back down or does it cool fairly quickly?

[Compdoc]

If you enlarge the original picture, the by-pass hose looks pretty swollen, so definitely worth a look. As Nick says, fill up with water, run the engine and start looking for leaks. Check all hose connections and water pump seal.

If it overheats with no leaks then a flush with rad-flush and a new water pump can be done for around £25.

[Twincam]

Regarding what Compdoc has said. Buy some silicone pipe with the same interal diameter and cut to size. The fluted ones don't last as they're more an emergency one.

[Boycie]

Has the car stood for much of its life?
I think I'd agree with Moke regarding rust in the water jacket. I fitted a low mileage 998 in my blue car that had been 'resting' for many years. Before I fitted the engine I took the opportunity to thoroughly go over it in the hope it will be reliable.
I removed the core plugs from the block and couldn't believe the shale build up in there. I reckon the debris was taking away half the coolant capacity. My engine would have run very hot just where you don't want it to- around the cylinders!

I would fit a Minispares evo pump with new bypass hose. Thoroughly flush the block with a hosepipe with the pump off. Flush the rad in both directions. Run around for a week or so with plain water in the system, then drain again and refill with proper coolant.

[JCmini]

Hi generally it cools down after a slow 20mph drive or even sat in traffic. Its only under load going uphill or fast on motorway it over heats. 

 

I will take the water pump out and have a look at it. 

 

Whats a water jacket and how do I check it?

[Boycie]

Yes, that's because the engine is working hardest under those conditions and therefore generating more heat.
The water jacket is just terminology for the space in the block around the cylinders. Obviously, this is normally full of water and this water (coolant) transfers heat away from the source and allows the engine to stay at an optimum temperature, mainly governed by when the thermostat opens.
What you describe also points toward a clogged rad but I'd be doing a 'belt n braces' fix here and clear out everything. Your engine can only benefit from it.

[Spider]

OK, so as Boycie touched on, it does sound like it's making too much heat rather than an inability to off load the heat.

 

As Boycie also suggested, flush the cooling jacket (system). There's many threads here on the forum with some great suggestions if you do a search.

[imack]

Check the pump impeller is not loose on shaft when hot.
I once had an overheating problem, 30 years ago so I can't remember all the details.
Water level would drop in rad when engine was revved when cold as nicklouse mentioned but the impeller didn't pump when hot. Remember testing this by getting the engine hot and removing the heater hose from the heater valve on head and then start and revving the engine with the valve open, very little flow from the valve when hot, but gushing when cold.
Pump removed and when at room temperature impeller couldn't be turned independently of shaft, pour hot water on it and impeller turned freely on shaft. Always been wary of plastic impellers since!

[Boycie]

May be a bit OTT but I never refit a used water pump unless it's only a few months old. But I can understand that's not realistic if accessibility to new, cheap parts isn't so simple.