Gasket Leak on my K-series :o(

[CageyH]

Does the bottom radiator hose get too hot to touch?

 

[Dangerwheels]

The bottom radiator hose was very cool. The inlet hose to the top of the radiator was reasonably hot, the external water rail feeding along to the top of the radiator was hotter (though it is thin metal rather than thicker hosing, so will heat up differently to the coolant temperature inside in the short time the engine was started). I did drive the car down to the bottom of the road and back (300m), on this fine cold frosty day some cool air will have passed across the radiator, which could account for the temperature of the bottom hose. Though the potential lack of circulating coolant could cause this too.

 

I'll try the free check as suggested (thanks ECR) and see what happens. If no good i'll be checking the water pump during the week.

[Bio]

Sounds like the dreaded air lock problem...or a thermostat that will not open ☹️

[Mort]

I'll keep on asking his question, because I'm really concerned about it - my bottom hose is alway quite cool (1.4K) but everything else seems OK ( temperature gauge,fan cutting in, etc). Does this indicate a potential problem?

[John Vine]

Quoting Mort: 

I'll keep on asking his question, because I'm really concerned about it - my bottom hose is alway quite cool (1.4K) but everything else seems OK ( temperature gauge,fan cutting in, etc). Does this indicate a potential problem?

Didn't we answer that here? 😬 Or have you received conflicting opinions?

 

JV

[Often in France]

Having had similar problems as described on my 1.4K, i.e. running hot, bottom hose cold and difficulty bleeding the system I changed the thermostat, took it out and drilled a 3mm hole, changed the expansion bottle cap, fitted the bleed T piece, massaged hoses and had a "sniff test" that indicated that the head gasket was OK. We also poked the little ball valve next to the inlet manifold and water flowed OK.

Eventually we noticed a weep just below the inlet manifold, not easy to spot as the coolant was evaporating quickly on the warm engine. Set about changing the inlet manifold gasket (green thing) and it became obvious that the ball valve was not working correctly as it was sat in gunge. Gave the area a good clean fitted the new gasket, also replaced all the hoses with silicone ones from the bulk buy. Filled the system and bled simply via the T piece and everything has been spot on since.

[charlie_pank]

When building the R1 I had an engine which had been totally emptied of coolant for some time. It took me several attempts to fill it. You need to employ some common sense to remove airlocks, the best thing I can recommend is to loosen all the hose clamps, bleed screws etc..., and then fill the system slowly and do up each hose clamp as it starts to leak, making sure that it is no longer leaking any air, only coolant.

 

As mentioned already, even if your temp sender is duff, it won't cause overheating. That will only be caused by a) lack of coolant somewhere, b) water-pump not pumping enough volume of coolant, c) radiator fan not coming on, d) thermostat not opening, e) engine putting out too much heat due to running lean or being mis-timed.

 

How do you know that it's currently overheating? You know that the system SHOULD be pressurised when up to temperature right?

[Mort]

Quoting John Vine: 

Quoting Mort: 

I'll keep on asking his question, because I'm really concerned about it - my bottom hose is alway quite cool (1.4K) but everything else seems OK ( temperature gauge,fan cutting in, etc). Does this indicate a potential problem?

Didn't we answer that here? 😬 Or have you received conflicting opinions?

 

JV

You did John, yes - and I'm grateful for that. However, I've become paranoid about this, which is why I'm seeking reassurance.

 

Edited by - Mort on 3 Dec 2012 13:33:55

[John Vine]

However, I've become paranoid about this, which is why I'm seeking reassurance

Understand perfectly.

 

JV

[Bio]

Nick

Did you change your hoses recently 🤔 Does the temperature behave the same as before 🤔 Did yur bottom hose stay cool before 🤔

If your temperature is normal and the fan cuts in and out I would think all is ok.

 

John

[Dangerwheels]

As mentioned already, even if your temp sender is duff, it won't cause overheating. That will only be caused by a) lack of coolant somewhere, b) water-pump not pumping enough volume of coolant, c) radiator fan not coming on, d) thermostat not opening, e) engine putting out too much heat due to running lean or being mis-timed.

 

a) is a possibility. I made the K-series coolant mods as per the Sept LF issue, and managed to get 5.1l of coolant in the system (also by raising the nose). I'm reasonably confident there are no major airlocks.

b) is a distinct possibility - i'll be taking the pump off on Thurs and will see if the spindle is operating correctly.

c) As the bottom rad hose was cool, either the Rad is doing its job, or theres no hot coolant being pumped into the Rad (as a direct consequence of (b)), so until i've verified the water pump i won't know whether the switch is bust.

d) Got a new thermostat now. Have to assume thats working (though can check if necessary) otherwise i've been sold a dud.

e) once (B) © and (d) are verified, if its still overheating, i'll look into this one.

 

Currently i'm hopeful that the water pump is faulty. I'm not sure how cool the coolant exiting the rad should get normally, but it was barely warm (may just have been my cold hands!). If hot coolant isn't being pumped around the system, then the coolant in the rad will never get hot enough for the fan to come on in the first place. This may point to localised heating (i.e. in the engine) thus the pump may well be at fault.

 

[John Vine]

If hot coolant isn't being pumped around the system, then the coolant in the rad will never get hot enough for the fan to come on in the first place.

Worth bearing in mind that the fan sensor is in the rad header (and therefore in a hot place), whereas the coolant exiting the rad will be cool(er) -- by design. For the moment, my money's on the pump too.

 

JV

[Tony Whitley]

Without actually testing this, I think that if the engine is hot enough that it's overheating then the coolant going back into the engine should be almost as hot as that leaving the engine as there's little to have cooled it unless the fan is blowing air through the rad or the car is moving.

 

If the bottom hose is cool then there's no flow through the system - stuck thermostat, a big air lock or a knackered pump.

[Mort]

Quoting BIO: 

Nick

Did you change your hoses recently 🤔 Does the temperature behave the same as before 🤔 Did yur bottom hose stay cool before 🤔

If your temperature is normal and the fan cuts in and out I would think all is ok.

 

John

Hi John

 

Yes, hoses changed to silicon during the last service (by Caterham specialists - I don't much enjoy spannering these days). Temperature was running higher initially, but it's been back and been re-bled /checked and now seems OK. I can't say whether the bottom hose ran at a similar temperature before the service, as I never had an issue with temperature before the service, and so hadn't checked it. It does, however, seem to be only warm when the heater is off, and cooler still when the heater is on. I did mean to speak to you about this at the last Penn meet, but somehow forgot about it. Grateful for your thoughts.

 

Sorry about the thread hijack, BTW, but as this may be connected to the OP's problem it may be useful.

[charlie_pank]

You still haven't said how you know it's overheating.

 

You can test the fan switch in the rad by testing its resistance as you bring it to the boil in a pan of water - should see resistance drop when it wants the fan to come on.

 

Note that the fan switch is at the top of the rad, if you open up the bleed screw in the top of the rad, and take it out, then loosen the expansion cap for a second, does coolant come out immediately, or is the rad switch sitting in an air bubble at the top of the radiator?

 

You should be able to test that coolant is flowing without having to take the water pump out - how about turning the engine over on the starter motor for a couple of seconds while the pump's intake is in a bucket of water and the output is directed back at the bucket - you should be able to see it flow!

[Dangerwheels]

You still haven't said how you know it's overheating.

 

I have both coolant and oil temperature sensors on my seven, and can flick between the two readings from the dash. When the coolant needle reading heads past 80Deg and doesn't stop its not good news I'm thankful it had this sensor - i could have blown it again after the rebuild. That would have been *really* embarassing.

 

When i stopped the engine last week after it got hot, i did check the bleed screw on the top of the rad - coolant immediately bubbled out after only a turn of the screw. Thats what makes me believe the top of the rad contains coolant and not an air pocket (which as you state would alter the temp reading for the fan as it would be sitting in a warm/hot air bubble and not in fluid).

 

I also half undid the expansion bottle cap, and could hear the coolant system depressurise (if thats any help).

 

An interesting idea on checking the water pump - I'll be taking a look on my day off later this week :) Thanks.

[charlie_pank]

Test the temp sender and gauge with a thermometer and a pan of hot water.

 

If you undid the bleed screw while the system was hot and therefore pressurised, you'd get water coming out virtually instantly even if there had been an air bubble trapped there.

[Dangerwheels]

Note that the fan switch is at the top of the rad, if you open up the bleed screw in the top of the rad, and take it out, then loosen the expansion cap for a second, does coolant come out immediately, or is the rad switch sitting in an air bubble at the top of the radiator?

 

Thanks for this tip - you were quite right. I warmed the engine up, then let it it cool down. About an hour later i checked the coolant level in the top of the radiator - it had dropped by almost an inch. Air pockets. So i topped up and repeated the process - only a small air pocket this time. But i also noticed that the heater would not pump out any hot air, which i am taking to be an air pocket at the top of the system too. And after all my attempts to raise the nose as high as possible too during the refill. D'oh.

 

I have just purchased a Coolant bleed tee which will hopefully arrive amongst the xmas post next week ( if anyone still requires one, the ebay sale is eBay Coolant Bleed Tee). Once that is fitted i will try again.

 

With the heater and the extra piping for the LowFlying coolant mod the system must now take more than the 5.1l of coolant !

 

[elie boone]

Since you will do the coolant mod, if you have enough room between rad and nosecone you could put a banjo in place of the bleed screw, your rad would not trap any air anymore. You could plumb this in with a T piece on the small ho se from the expansion bottle.

[Tony Whitley]

im a-leanin' on a lamppost

At the corner of the street

In case a certain little lady comes by.

 

I don't see how that's going to help

[Jason E]

I would say air lock as they can take ages to bleed and mine was unbelievably difficult even with a bleed tee , I was utterly convinced that I had all the air out on numerous occasions , however I did trace a slight weep on a hose joint that was letting air in so that sort of explains my prolonged experience.

i would be thinking why the car overheated in the first place maybe the head gasket but the water pump does raise a question for me , I have just done a golf with exactly that problem plastic impeller with steel shaft which I think the k series is

[Stationary M25 Traveller]

When I replaced my k-series water pump, the new one had a steel impeller.

[jj48]

Have never seen a " plastic impeller " on a k series motor and have replaced a few over the years!

Regards

Richard

[Jason E]

i wasnt sure about the plastic impeller so bow to your knowledge , obviously i was dealing german inferior parts!!

[Dangerwheels]

Done. Fixed. Phew. Hurrah!

 

Fitting the bleed tee into the system by the heater coolant inlet/outlet has made the world of difference to ensuring enough coolant is in the system. I'm sure the system is now taking in more than the 5.1l of coolant (i've topped up/lost so much coolant in tinkering i've lost count of actually how much is in the system), but the tee has allowed me to ensure easily that enough coolant is in the system. Had to top up a few times through the bleed tee following short runs in the car, but its now steadily holding temperature at 85-90 deg, i had a lovely run around some of the local roads and it behaved just like it ought to. Its like having a new car all over again :)

 

If anyone experiences any overheating issues i'd highly recommend fitting a tee-piece into the coolant system. If nothing else, it only cost a couple of pound for the parts - including an additional pair of hose clips, and makes it so quick and easy to see and diagnose the coolant levels.

 

Cheers very much everyone for all your assistance and comments, the whole head gasket change has been a great learning experience and i feel like i know an awful lot more about whats going on under the engine cover than ever before.