very strange problem this morning which has ruined my day......

 

car was fine yesterday but this morning on my way to work i noticed that my digital spa temp gauge was only slightly above the amb temperature. this stayed like this for about 10mins which was very strange and then suddenly lempt up to the usual temp of about 70C then started wobbling about between 50-80C then pulling into the work car park it started rapidly spiralling upto 90 and beyond and reached 105C when i pulled into a space and shut the engine off.

There was steam coming out from the bonnet and when i lifted it there was coolant spraying out of one of the hoses that connects to the head.

 

I topped the rad up with water after work and tried to drive it the 8 miles home. It did a similar thing and the start with only slightly above amp temp then suddenly rockets up to 90s when i pulled over and turned off. coolant spraying out again. called out the breakdown cover and got it towed home.

 

Now i need to know what to do to fix it.

 

there doesnt seem to be any hoses that have pulled off and cant see how i have cracked the rad when it was standing still. the hoses felt spongy and obviously not full with water like it was being pumped. the spa gauge sensor is on the rad top hose. the rad felt cold when overheating and only the two pipes to/from the block seemed (VERY) hot. the fan is turning.

 

 

Seems like the water isnt being pumped and the coolant in the block is boiling up and pressurising the hoses and pissing out the fluid. Took a long time for that to happen on the way to work so maybe the problem was intermittent. Maybe the only strange thing i noticed before this happened that could be related is that the morning before when i had turned on the blowers to get some heat in the water temperature dropped a bit which i thought was strange and didnt think had happened before but it was quite cold. Dont think temp dropped below 0 and have plenty of antifreeze in system so dont think ice cracked rad or pipes.

 

waterpump? thermostat stuck open/closed?

 

i hope i havent bent my head gasket with the heat. It was only slightly above 100C according to the temp gauge for a few seconds. how can i tell that it is bust apart from the mayo on the oil cap?

 

Apologies for long message but really need some help.

sound like thermostat or maybe blocked rad

what do i do to fix it? how could the rad be blocked? did a full flush through before xmas so pretty sure there can be an major debris

Take the stat out and test it in some very hot water

 

normally says on the stat what temp it will open at, check it with a thermometer

 

find the leak as well and change the pipe, might be a small crack that doesn

t leak till the pressure gets up

 

If the coolant system is not pressurised due to a small leak then the water will boil and the car will overheat anyways

 

your water pump is belt driven so it will be spinning, worst that can happen with these is a broken blade or failed bearing but you would hear it grinding.

cant hear any bearing sounds but there is some belt squel probably down to coolant being sprayed all over the front of the engine bay.

 

does the stat sound like a likely diagnosis of my problem to everybody?

cant hear any bearing sounds but there is some belt squel probably down to coolant being sprayed all over the front of the engine bay.

 

does the stat sound like a likely diagnosis of my problem to everybody?

cheapest and easiest first point of call. start simple imo! oh and fix the leak ;)

i suspect the hoses between the heads are leaking.

 

top up the cooling system and let it tick over and watch it for leaks as there is bound to be one.

get the system pressure tested this will show up any leaks and weak spots in the system

I understand their can be a small leak somewhere that wil be letting fluid out a high temp = high pressure but what is the original major problem that was causing my wierd temp problems. I am going to check the stat out now but if it wasnt that what else it could be?

air lock, if you have had the system drained or lost water

ok i have removed my thermostat and tested its opening in a saucepan. I didnt have a thermometer on me so cant tell the opening temp but it was opening before boiling and shut relatively quickly when dunked in cold water. I am going to replace it for a new part as i have got it off but i have seen that it does open so it ws not jammed.

 

So what else could be causing my problems. I can test for leaks in change the rad cap when everything is back together but what else can i check out now with the rad and feed pipes etc detached?

you will need to replace the 2 short rubber hoses that go into the engine from the metal rad pipes, these are prone to leaking especially if they have been disturbed. process of illimination i think mate, i still think you had an air lock if you have no signs of a water leak

have you checked the edges of the rad as they are plastic and it has been known for them to come away?

rad should be fine. It is a aftermarket copper core with copper side tanks. I reckon the leak from pipes/radcap then air lock phenomenon sounds the best bet.

I think replacing the water pump is just beyond me because of the belts and pulleys so i am going to put back together with the thermostat and small rubber pipes replaced and sit it on a hill with the rad cap of and try and work out any air locks.

 

Where is the best place to get the short bits of pipe? i guess they are nissan only, if so any idea of the part number, or do one of the traders do them? Is there an upgrade on the rubber (silicon or something less prone to spliting?). Also what is the best place to get the thermostat although i have seen them going on jap parts web sites for about £25.

 

Thanks for all your help espeacilly Carl.

rubbe rpipe about £5 off Mike at MJP in traders sec. He'll prob sort you out with thermostat too

got the small rubber tubes and thermostat for a great price. Very helpful and knows what he is talking about. glad i didnt make it to Japarts before they shut on saturday because they were charging more for the stat than mjp has charged me for the lot!

 

would people recomend these incase it is the main rubber pipes that have the leak?

http://cgi.ebay.co.uk/Nissan-Z32-300ZX-Fairlady-Silicone-Radiator-hose-kit_W0QQitemZ290098151401QQcategoryZ72205QQrdZ1QQcmdZViewItem

seems pretty pricey but surely these longer tubes are more likely to have the leak as they are longer??

 

are the silicon tubes better performance and longevity or are they just for the bling?

air lock, if you have had the system drained or lost water

I would say so it's very easy to get an air lock, when you re-fill the coolant start the engine run it for a short time then check the level again. Do this until the coolant stays at the top.

Normal running temp should be 84 degrees so if your car is running at 70 C then it either has a Nismo type racing thermostat or it is sticking open. This can quite easily hit 95 C after a serious bit of kaning, but it should fall back to 84 C quite quickly. So you may have a air lock, but you have to ask why?

 

Don't want to upset you, but this has the ring of a head gasket failure. Check for traces of oil in your water. If no oil then the next thing to check is the Rad cap. These rad caps are a presure regulator and should allow water to flow out to your expansion tank at 7psi which means your coolant system shouldn't presurise to the degree your saying.

 

I'd change your rad cap for what its worth and I really hope it is just the Hoses, thernostat or rad cap.

you are scaring me! think head gasket should be fine as there is no mayo on the oil and havent noticed any oil in the coolant after being covered in it for the whole weekend. There is a very very slight film on the puddle of it from the car but this was most likely picked up from the cr@p on the road or a bit of grease it could as it was flooding down my engine.

I would say normal running temp for my zed would be about 77C-ish and has been pretty rock solid since i did a thorough engine flush and installed a copper core rad about 5 months ago. I have seen plenty of posts on here where people have differing average temps and mid 70s to mid 80s sounds the right range. I suppose it can depend on all sorts of things like rad condition, coolant condition, number of waterways blocked in the block, oil used, whereabout the aftermarket sensor is placed and how accuratly it is calibrated.

 

thermostat is nissan, did seem to open and close pretty slowly and not sure of the temps this was happening but will know better when i have the new one to compare it against. also there is nothing to say it behaved the same in the engine as it does in a saucepan of boiling water.

 

What other signs can i use to identify head gasket failure?

I'm not deffinately saying it is. However the reason I said this is because, this is exactly how mine started. Also three people i personally have known who have had head gasket failure has started like this. The other tell tale sign can be heater Matrix failure. Then having replaced the water return hoses from each head (the short rubbe pipes or matrix) full head gasket failure has occured within a couple of thousand miles.

 

What I'm saying is get it tested now. You need to be able to do a presure test on your system to eliminate it as a problem. If it is presurising it gives you time to either sell it or bite the bullet and have the work done.

 

If it is a real small split it may just let gasses pass under combustion. This presurises the system. It will leave an oilly film in the water but won't turn the oil into mayo. The presure builds up then will find the weakest point of the system. ie brittle hoses that should be replace every 60K or 5 years same as the cam belt, but seem so often not to be. Or a corroded and on its last legs Heater Matrix. Any half decent proper old style garage can presure test your system. I assume, but someone like Duffers could clarify. that if the Rad cap regulates at 7 psi that the water system shouldn't exeed 7 psi.

heater matrix failure would be wet passenger side carpet which is dont have. any other tell tale signs of heater matrix failure?

Is pressure testing my system putting a rad cap on the rad with a hand pump attached and pressuring it up (to 7psi???) on the hand pump gauge and seeing if it holds that pressure?

This should be something that EVERY garage has trouble is that there arent many friendly and honest garages in london that would do it without charging and sucking their teeth and trying to generate themselves a lot of cash by saying it is on its way out. Just wish the zen garage wasnt so busy or i would wip it round there without feeling guilty that i was bothering the guys there. Or is there anyone in london with one of these pumps and the knowledge of how to spot the warning signs????

The garage puts a rad cap blank on and then attaches a gauge to the overflow/ expansion pipe and mesures to see if your system is being presurised. If it ain't that one less thing to worry about.

 

Sorry to be a pessimist, but if it is that its better to know as it gives you options to hide it and sell or fix it.

definetly mate. Thanks for the tip off.

 

Is the method i have described to test something else or a different way of doing the same thing. In your method are you testing the whole system pressure capacity without a working/sprung rad cap? does the system have to hold the pressure for an amount of time or are you just testing to see what pressure it can get up to?

 

Any ideas on what that target / test pressure should be?

what Mark has said about the HG has got me really woried and doing searches seems like many people have had the same symptoms as me and it was down to a failed HG. Although, i think it is just as likely to be a leak from one of the hoses or a faulty rad cap I am keen to find out whether my HG is in trouble.

I have read about a "sniffer" test with dye chemicals to test whether there are exhaust gases getting into the water system. I know there are other methods to test but these all seem inconclusive and i have seen a post that says this test kit only cost £25. However, i have searched the internet and cant find anywhere that sells it (it is just mentioned on every other car club forum which goes to show that is not only zeds that are a headache!). Does anyone know where i can get it or even a brandname that i can search for?

what Mark has said about the HG has got me really woried and doing searches seems like many people have had the same symptoms as me and it was down to a failed HG. Although, i think it is just as likely to be a leak from one of the hoses or a faulty rad cap I am keen to find out whether my HG is in trouble.

I have read about a "sniffer" test with dye chemicals to test whether there are exhaust gases getting into the water system. I know there are other methods to test but these all seem inconclusive and i have seen a post that says this test kit only cost £25. However, i have searched the internet and cant find anywhere that sells it (it is just mentioned on every other car club forum which goes to show that is not only zeds that are a headache!). Does anyone know where i can get it or even a brandname that i can search for?

 

Try Demon Tweeks

 

01978 663058 or 663006 or 663024 I'm sure they do the sniffer test thingy