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Old 13-10-2013, 15:52   #1
philiptrak
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MGZT coolant problems

Hi Guy's i am a new member so bare with me, but need some advice with my 1.8 K Series MGZT 120+. My car is an 04 plate with 98,000 on the clock and with the usual issues all fixed head gasket, fuel filter, all this has been done over the life span of the car and all seemed well, but over the last few weeks my car has started loosing coolant through the expansion tank cap and is doing the same through a brand new genuine rover one as i thought it might be the old one had failed. The interior heater is working as it should, the car is not overheating only when it has lost most of the coolant and then the fan kicks in as it should, i immediately stop let it cool and fill the system back up. I check the water level every day, the level stays fairly constant but under pressure sometimes when cold and overflowing from the expansion tank when i remove the cap after the car has stood all day which i know is not normal, the problem usually starts when i am in slow moving traffic. I have had a mate who is a mechanic look at it but the car fails to play up every time he has it for a day so both of us scratching our heads, i really don't want to get rid of it as this is the best car i have ever had and i am hoping it is something simple any ideas?
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Old 13-10-2013, 16:13   #2
T-Cut
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The signs point to another HGF in progress I'm afraid. Repeatedly allowing coolant to get so low as to cause red light overheating is only exacerbating the situation. When the warning pops on, it's often too late to prevent damage, however small. That's why many of us with 1.8 models fit proper temperature gauges.

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Old 13-10-2013, 16:21   #3
philiptrak
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Thanks it was an uprated head gasket that was fitted, and so far no mayo on the oil stick or the oil filler cap, recently had an MOT and the exhaust test all came back normal car running fine so really confused as to what is causing the pressure problem as i said the interior heater is working fine it has only overheated twice but it is difficult to know the car is losing coolant as it does it when driving through the expansion tank cap.
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Old 13-10-2013, 18:21   #4
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Assuming the pressure relief cap is in working condition, the only way that coolant can be ejected is for the cooling system pressure to exceed 22psi. Over-filling can cause hydraulic lock ejection, but that doesn't seem to apply from what you've said. Over-pressure can happen if there's an excessive overheat (to around 128-130C) which will raise the vapour pressure in excess of the relief pressure, or for exhaust gases to be pumped into the cooling jacket via a fissure in the head gasket. This can happen by failure of the gasket material, if the head surface is untrue, the liner protrusion is too small for the gasket system in place or lack of tightness in the head clamping bolts. Another cause could be a crack in a cylinder liner.

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Last edited by T-Cut; 13-10-2013 at 18:28.
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Old 13-10-2013, 18:43   #5
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When the engines up to operating temperature squeeze the top hose.
If its hard, you have a problem.

It could still be head gasket related.

Since it would be most likely getting combustion pressure in order for it to overpressurise (rather than the engine over heating)
A sniffer test on the coolant would work.

It might be that its leaking coolant from somewhere.
This would lead to air in the system which expands and pushes water out.

You need to decide which case it is
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Old 13-10-2013, 19:52   #6
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Quote:
Originally Posted by richardszt View Post
When the engines up to operating temperature squeeze the top hose.
If its hard, you have a problem.

It could still be head gasket related.

Since it would be most likely getting combustion pressure in order for it to overpressurise (rather than the engine over heating)
A sniffer test on the coolant would work.

It might be that its leaking coolant from somewhere.
This would lead to air in the system which expands and pushes water out.

You need to decide which case it is
I'm with the above comments. For peace of mind you could get a head gasket test done (gas or dye test) to confirm if it is the head gasket or not. X
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Old 13-10-2013, 23:17   #7
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One other thought, how full are you filling the expansion tank? The MAX/MIN level indicators are actually right at the bottom of the tank below the fins, anything above this is likely to be expelled when the engine reaches the correct operating temperature. If you are overfilling it may be the engine is just finding it's own level and you have nothing to worry about.

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Old 14-10-2013, 07:55   #8
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Thanks Guy's will take all this on board and try and save my car from the knackers yard.
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Old 14-10-2013, 14:21   #9
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I don't want to hijack this thread, but my ZT-T 1.8 Turbo is showing similar symptoms. I've had 2 hoses burst in the last two months. The first, back at the end of July caused the needle to top out and the overheating warning to flash up on the dash. The second was better managed, and only saw a brief, slight rise in temp. Since then I've continually had to top up the coolant - not sure of quantities, but I've started to monitor it now. No mayo, and there's always pressure when I take the cap off, even after a couple of days of no use. The fan only kicks in occasionally when stuck in traffic for an extended period. Heater works fine.

Never having noticed the "Max" mark in the expansion tank because it's usually covered by coolant (nice bit of design genius there!), I've often over-filled it (but no more!). Is it worth changing the cap, and/or should I be worried about hgf?
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Old 14-10-2013, 16:06   #10
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Don't be fooled by the level of water, i went several days without topping up always making sure the water level was just below the fins in the expansion tank, and then for some reason i lost the lot again! out of the pressure cap and that lead to overheating. I stopped the car immediately let it cool and then topped up the water it took quite a lot before it found a level again so it is really difficult to know how much to keep adding. You probably already do this but keep plenty of water on board and check the expansion tank every day. My car is being looked at over the next couple of days with various tests will keep you posted.
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Old 15-10-2013, 07:50   #11
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Well, I'm not sure if I noticed a new symptom today or not. Cold morning and a very steamy exhaust, although it did seem to clear up after the engine warmed up. I suspect I'm just being paranoid because coolant loss is on my mind, but it did seem a lot steamier than any other car around me. It was very noticeable when sitting in traffic, but less so once moving. Haven't checked the coolant level yet, but will pop down at lunchtime and see how much it's gone down since last week.
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Old 15-10-2013, 11:28   #12
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Excessive steam production can be a sign of inlet manifold seal failure. This is common in the 1.8 engines and leads to coolant loss with no outward signs. The coolant will usually get into cylinders 1 and/or 4 causing their spark plugs to look 'washed' and get a pink stain. The fix for this is a new seal. The best option is the later Viton version (black). The original seals are in a less robust blue coloured rubber.

Viton Seal: http://www.rimmerbros.co.uk/Item--i-LKJ101110
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Old 15-10-2013, 12:52   #13
JensenHealey
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Excessive steam production can be a sign of inlet manifold seal failure. This is common in the 1.8 engines and leads to coolant loss with no outward signs. The coolant will usually get into cylinders 1 and/or 4 causing their spark plugs to look 'washed' and get a pink stain. The fix for this is a new seal. The best option is the later Viton version (black). The original seals are in a less robust blue coloured rubber.

Viton Seal: http://www.rimmerbros.co.uk/Item--i-LKJ101110
Well, I've just ordered both a new expansion tank cap, and a new IMG. Give me something to do at the weekend...
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Old 15-10-2013, 13:07   #14
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Fingers crossed that sorts it - on a K4 engine I'd always change the IMG if you have any coolant loss or odd coolant behaviour - they're weak and fail often.
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Old 15-10-2013, 14:32   #15
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Fingers crossed that sorts it - on a K4 engine I'd always change the IMG if you have any coolant loss or odd coolant behaviour - they're weak and fail often.
I read somewhere that the older alloy manifold is better in this respect. Is it a straight swap? (assuming they can be obtained...)
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Old 15-10-2013, 16:40   #16
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Had a test done to find out if there was gases in the water and all clear so no HGF, and cylinder head also ok, but still no answer to the pressure build up in the expansion tank when it has been left cold. At least it behaved itself this morning in heavy traffic no loss of coolant through the cap so still head scratching at the moment .
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Old 15-10-2013, 18:13   #17
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Possibly a p**s in the dark but if running in slow traffic starts the temperature rising i wonder if the thermostat is working properly? or the fan sensor? is the rad core gummed up with crud? just floating ideas, cheers Rob
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Old 18-10-2013, 08:03   #18
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Well after doing a gas test and all came back ok, the last few days the car has run perfectly fine. Maybe this is a tip for anyone else with a similar problem, the last time i took the expansion cap off when the engine was cold and the coolant came straight to the top and overflowed i kept pumping the top hose with my hand forcing more coolant out until the level settled just above the max, maybe doing this helped force some air, i really don't know, and i hope it's that simple, but i have been stuck in traffic, done some heavy motoring and no coolant loss through the cap and keeping a constant water level in the expansion tank, fingers crossed, and thanks for all the help and suggestions will keep you posted. cheers
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Old 18-10-2013, 08:36   #19
JensenHealey
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Originally Posted by philiptrak View Post
Well after doing a gas test and all came back ok, the last few days the car has run perfectly fine. Maybe this is a tip for anyone else with a similar problem, the last time i took the expansion cap off when the engine was cold and the coolant came straight to the top and overflowed i kept pumping the top hose with my hand forcing more coolant out until the level settled just above the max, maybe doing this helped force some air, i really don't know, and i hope it's that simple, but i have been stuck in traffic, done some heavy motoring and no coolant loss through the cap and keeping a constant water level in the expansion tank, fingers crossed, and thanks for all the help and suggestions will keep you posted. cheers
Hmm, well, I put a new cap on yesterday, and although I've only done 4 short (~4 miles) trips since, the coolant has dropped by about 1/4 pint. Also, there was no pressure when I took the cap off ths morning - is that right or wrong? It also seemed a bit lumpy on start-up from cold, so I'm definitely thinking inlet manifold gasket. New Viton one turned up on Weds, so I'll get that fitted overthe weekend and see if that sorts it.

{Edit} Anyone got a spare inlet manifold nut? :-(

Last edited by JensenHealey; 19-10-2013 at 11:45. Reason: Update
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Old 19-10-2013, 11:56   #20
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JensenHealey;6082378]Hmm, well, I put a new cap on yesterday, and although I've only done 4 short (~4 miles) trips since, the coolant has dropped by about 1/4 pint. Also, there was no pressure when I took the cap off ths morning - is that right or wrong? It also seemed a bit lumpy on start-up from cold, so I'm definitely thinking inlet manifold gasket. New Viton one turned up on Weds, so I'll get that fitted overthe weekend and see if that sorts it.


{Edit} Anyone got a spare inlet manifold nut? :-(
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