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Z20Let Coolant Loss


steve_wilson
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Morning :)

 

I'm having a few issues with my 2B that I've fitted a Z20LET to...

I'm thinking head gasket/cracked head, but I just wanted a second, third and fourth opinion before I start stripping it down.

 

It's a rebuilt engine (by myself) with new gaskets, seals and water pump, new civic aluminium 50mm thick radiator (shrouded), new hoses and a nice big oil cooler. I have removed the thermostat.

The grill in the nose cone is one of the Caterham type ones so isn't restricting flow, and I've fitted flared side panels to remove heat from the engine bay.

 

At speeds of above 50mph-ish the temperature will creep up and up and eventually start blowing past the rad cap (which I believe is a 20 psi one).

I've also had a few little slow drives around the estate on a cool evening with no bonnet fitted and the same issue occurs but much slower.

 

in 50 miles of use I've used roughly 3 litres of water.

 

I bought one of the testers off ebay that tests your coolant for combustion gasses which has indicated there are no exhaust gasses present in the coolant.

 

The next thing I'm planning on doing is fitting a pressure gauge and Schrader valve to a coolant pipe, pumping up with a tyre pump and looking for pressure drop... which I think should rule out any coolant leaks in the system.

 

Despite the coolant tester indicating no exhaust gasses in the coolant, I still consider head gasket to be the most likely culprit. Although would it be possible for the water cooled turbo to be leaking coolant into the exhaust somehow? Perhaps its possible for it to be airlocked - how do I rule this out?

 

The exhaust gasses are quite smokey/white but that could just due to the low temperatures outside. There are no other running issues. it pulls very well and isn't making any usual noises.

 

Advice/opinions welcomed

 

Thanks,

Steve

Edited by steve_wilson
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So I've no experience of that particular engine, but a couple of things I've learnt with others...

 

Rover K-Series can have hot spots in the water gallery at the front of the head; there's a small take-off on the front of the head (through the inlet manifold) to ensure even flow and no air collecting there. But a number of people fit aftermarket manifolds and then block off the water take-off, causing issues with warped heads. Is there any chance anything like this has happened with yours?

 

On running without a thermostat - some engines can be fussy about this. On my race engine, a Peugeot XU10J4R lump, I was advised for race use it was adviseable to leave it out to counteract hot spots within the engine... but "no thermostat" means you keep the thermostat outer ring, you just remove the sprung assembly in the middle, to presumably keep some degree of "port" for the water pump to push water through and maintain some sort of flow rate? With the K-Series, a number of people run it without a stat but I have found that to be a very bad idea, the engine never warms up fully and there was ultimately no need - if the car was overheating then the last thing that should be causing this is the thermostat (edit: other than it being stuck, of course!), so they were just masking other issues.

 

Now, like I say, there may be specifics for your engine that I'm unaware of so take all of the above with a pinch of salt. Ultimately the water must be going somewhere, right?! So if the system is sealed, it's not in the oil, it's not leaking or escaping directly out of the cooling system, then it must be going somewhere. Inlet manifold, any chances it's being ingested into the inlet somewhere? Otherwise, as you said, exhaust system/turbo? If you left the engine for a week and then inspected the bores with a borescope could you check for water ingress? Anything scary with a compression test (not always a sure-fire indication that's all good, but easy enough to do)?

Edited by brumster
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If it was the head gasket, you'd have emulsification in the oil - just open the oil filler cap and look for a creamy deposit.

 

If the engine runs OK otherwise, sounds like you just have a basic over-heating problem. Sounds like the rad is ok (shrouded, ally etc) so is your cooling system OEM or something you made up yourself? Sorry, I know nothing about that engine...

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If it was the head gasket, you'd have emulsification in the oil - just open the oil filler cap and look for a creamy deposit.

What makes you say this, is this something specific to the Z20LET?

What happens if the gasket goes between a water gallery and the cylinder, without touching an oilway? Or are you saying this isn't possible with this engine?

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I convinced myself that Marlin had a blown head gasket as the coolant system kept popping hoses off once the car was warm. I did every test I could think of to prove it was the head gasket, I could not get hard evidence that it was. I ended up doing a leak down test on each cylinder and the results were all ok. In the end it was down to my cooling system set up causing a huge air lock. Worth exploring all options before you rule out the head.

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Some XE & LET heads were known to be porous....did you have that checked?

As Craig says above, check simple (cheap!) things first.

Rad cap, then an air lock somewhere in the system.

I found the OEM setup complicated to fit in the kit.

I simplified everything, I blocked the heater feed at the back of the head & did away with the

water feed into the bottom of the inlet manifold, but I still need to open up a top hose

when refilling it to allow the water to fill the top hoses.

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Hi Steve

don't know how you've plumbed up your cooling system but here's how I did mine which would run at 80 - 85 degrees all day long and only rise to 90ish when sat in traffic until the fan cut in.

 

Bottom hose from radiator to back of the water pump, but I also Tee'd the 25mm pipe from the inlet manifold into the bottom hose.

 

The 8mm spigot on the inlet had a short piece of hose with a blanking plug to use as a bleed point when filling the system.

 

Top hose went from the thermostat housing to the top of the radiator and Tee'd into this was the turbo cooling loop which went from the spigot on the stat housing, into the top of the turbo, out of the bottom and into the top hose near the rad.

 

I ditched all the heater parts from the rear of the head, fitted core pugs to the holes where possible and then a 10mm aluminium plate with the metallised gasket bolted on to cover the whole of the area.

 

Where is your intercooler mounted, is it in front of the rad? Could there be some heat transference to the rad or is it possibly blocking the air flow through the rad?

 

Why have you removed the thermostat, I ran mine with the 82 degree version. Water pumps are also another problem area on VX engines, some of the aftermarket ones just don't seem to be able to do the job for some reason.

Edited by steve in stockport
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Thanks for everyone's input, really is appreciated!

 

So I think what I'm going to do is, fit a thermostat, plumb the system the way that Steve and Kerry have it (as I think mine is slightly different), fit the Schrader valve to pressure test the system and then go for a few drives and see how I get on.

 

 

What is the best way to avoid getting air locks in the system when filling? Do I get the hose pipe on the top rad hose to blast water through?

 

Thanks,

Steve

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but I still need to open up a top hose

when refilling it to allow the water to fill the top hoses

 

|Fill up as normal via rad cap or expansion tank slowly but allow air to escape from the highest hose bu loosening the clamp.

Edited by Bob Tucker
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