Blown radiator.

[Barry Gadd]

Took the Z3 in for the MOT today.
The good news is, it passed the emissions test (I asked them to do this first as it failed last time and I replaced the cat)
The bad news is for some reason the pressure in the rad built up while on test and blew a sizeable chunk of the rad filler tank out. I couldn't believe it as I'd taken the car for a 12 mile drive prior to taking it to the test centre and the car was fine.
I'm now puzzled.
Why would this happen during the test as the emissions test where the car is deliberately revved up had already been done?
Should the filler cap have let the pressure down? (Does it work this way or is there another pressure relief valve somewhere?)
Does this build up of pressure indicate problems with the pump or thermostat or headgasket?
I've seen an ad for a Z3 filler tank only. I didn't realise these could be replaced. How do you couple up to the honeycomb and make a watertight seal?
Again sorry for asking such questions but I really thought the car would pass the test this time.

 

[jonco]

Sorry to read that Barry - you don't seem to be having much luck. I presume you mean the expansion tank - this may help to explain procedure http://www.zroadster.net/forum/viewtopic.php?f=5&t=36720&hilit=Expention+tank-
You can get a new tank from Eurocarparts or carparts4less for £20 to £30 including O ring seals.
Tanks do become brittle with age - no doubt others will comment on possible pressure causes.

 

[hard top]

Had this happen on a 318i.
I was told it was due to the thermostat and had to replace the radiator and the expansion tank.

 

[oldcarman]

Bad news Barry, doesn't sound like a head gasket but more like a stuck thermostat. Sometimes rad hoses collapse and can cause this also. Perhaps T-tony can give his opinion. JIM

 

[hard top]

This makes for quite a good story when it happened.
I was parked up at the airport waiting to pick up a friend of mine and parked up behind a Bentley. I had the engine running and the temp gauge started going up. The owner of the Bentley turned up and started to load his bags into the boot (trunk) with his backside inches from my car bonnet (hood) when it blew up. One hell of a bang and lots of steam, when the steam had cleared, I could see this chap laying on top of his bags in the boot (trunk) of his car. He climbed out, straightened his tie, gave me a dirty look and then got in his car and drove off.

 

[Barry Gadd]

Thanks for the replies.
I'm off this morning to tow the Z3 back from the test centre. Sounds like it maybe the thermostat so this will come off next then fit a new rad or just the expansion tank
Thanks for the story Mike. I needed cheering up. By the way, the MOT tester got a bit of a shock too.............. Didn't seem to have much of a sense of humour!!!!!

 

[badman gee]

Love to have seen the mot testers face!

 

[t-tony]

Not so funny when you're under a car inspecting it and a hose blows or radiator bursts and you get covered in nearly boiling.coolant. It has happened to me before, I wouldn't recommend it.

 

[hard top]

I had to get the car back from the airport the next day.
A colleague of mine offered to help (I should have known) and proceeded to tow me down the motorway at a million miles an hour, me with no power steering and hardly any brakes, we got to the last roundabout and the tow rope snapped and I thought, s***, that is going to hit me right in the windscreen but it did a lovely pirouette and took out his rear window....ha ha....

 

[Barry Gadd]

Had a white knuckle tow back home behind my Yaris driven by my neighbour . As you say Mike, virtually no brakes and really heavy steering but we made it.......
I took the rad out and the expansion tank is fine. A part of the black plastic radiator moulding had blown out. I've never seen anything like this before.
I searched ebay and found an identical rad in a breakers in Eastbourne so rushed down there and now have a replacement.
I checked the thermostat by heating in a saucepan bringing the temp to low boiling level. At this point the pin poking out of the top popped out. I'm not sure if this indicates it is working properly so I intend to replace.
I can't find a plug in thermostat on ebay for the M44 B19 unit and all I can find is the complete housing plus thermostat which I don't really need.
Does anyone know if we can buy just the thermostat??? The complete housing with thermostat fitted is around £30 and I'm more used to buying just a thermostat for other cars at around £5 to £10.
Thanks again for all your help.

 

[t-tony]

Hey Barry, you ought to be able to source a t/stat on it's own to fit your car without a problem. Do you have a local Euro Car Parts or Andrew Page?
If you PM me your reg I will ask our local's for price and availability for you tomorrow.

Cheers, Tony.

 

[oldcarman]

Hi Barry, was doing my usual trolling of ebayUK and found several thermostats for the z3 available for around 12-13£ HTH , JIM

 

[Barry Gadd]

Hi Tony / Jim,
The metal thermostat is marked 1743544.9 95* B9 2406. I removed it fairly easily from the plastic securing clips in it's housing.
I tried Euro car parts website but could only find the whole assembly (£33 from memory)
I searched ebay thoroughly for a thermostat for the M44 1.9L Z3 and could find several for the bigger engines (these look quite different from mine).
I searched for the part number on my unit but nothing came up.
Perhaps I will have to buy the whole assembly but it's a shame to throw perfectly good bits away when there's nothing wrong with them.
Thanks for helping.

 

[joey]

barry...thermostat and water pump are known weak points on the M44, I recently replaced both of mine and although on inspection of the old parts they didn't need it,

but you cannot put a price on peace of mind..

btw the thermostat comes in its housing and it is around the £30 mark..they are known to fail on "open" so it really doesn't have a huge effect on things most of the time, re the water pump, you can have my old one..still in great nick and with a metal impeller...probably has another 60k in it and would be a good swap out for yours if it is one with the plastic impeller...pm me if you want it and I will post FOC..seems like you are having a rough time with the Z, and could do with a break.

stick with it and you will be repaid tenfold by that car when she comes good!

 

[Brian H]

I had a blowout on my 1.9 some years ago, it was behind the expansion tank.

 

[Barry Gadd]

I've now got both a replacement radiator plus thermostat (I had to buy the complete unit, thermostat in it's housing) and will put these in this weekend.
I'm still puzzled as to how the pressure can build up and what is causing this. If the thermostat fails open then this should prevent a pressure build up. If it fails closed then I guess this could cause the increase.
Also my pump looks new. I would be surprised if it has failed. I will play this weekend and see if the pump can squirt water around.
We need a Jet D'eau in Pyrford............
Thanks for the offer of your spare pump Joey. I'm not sure yet if I need it but I will get in touch if the offer remains open.

 

[t-tony]

Good luck mate, keep us posted.

 

[David Cullen]

glad you got the full unit, housing and all, its always better to replace the full unit as the plastic t piece also has wear over a period of time and will also fail, good reading guys, some good stories best of luck with the fix

 

[Barry Gadd]

Having replaced the rad + thermostat I took the pump off and it looks fine to me ie the impeller rotates when you turn the driven shaft by hand and the o ring seal is fine. How does the pump fail? What would you expect to find if it has died?
Last thing I've checked is the viscous clutch cooling fan. I can stop the fan rotating with a roll of cardboard by gently pressuring against the rotating shaft. I've read that they do lose oil (or the oil degenerates with time) It seems as easy to stop the rotation with the unit both cool and hot so I've ordered a replacement.
Has anybody had problems with their fan unit? Do my symptoms sound like a classic fan failure mode?
Thanks in anticipation.

 

[zedonist]

I would expect the impeller to either be on the floor when taking it out or rotating freely on the shaft