给大家借鉴一下。MG7都快让人变成砖家了，整天提心吊胆，高度戒备！
冲缸垫
先兆1：排气白烟逐步浓重。左后镜明显可见。 排气味道越来越难闻。距2-3米明显可闻。
先兆2：打火时间明显拉长。抖晃明显。
先兆3：低速时水温升高明显。高速时可降低。水箱开始缺水，补加500毫升水温恢复正常。
水箱水或可见油花，及时修理，抬缸/换厚垫/换机油/机滤/防冻液。
　　汽缸垫装于缸盖与缸体之间，通过缸盖螺栓保证汽缸的密封，防止燃气、冷却水和润滑油窜漏。它必须严密密封汽缸内所产生的高温高压气体和贯穿缸垫的具有一定压力流速的冷却水与机油，并能经受住水、气和油的腐蚀。常见缸垫烧蚀是由于高温高压燃气冲击缸垫，烧坏包口、护圈及石棉板，导致汽缸漏气，润滑油、冷却水窜漏。出现冲蚀汽缸垫故障时，发动机动力性下降，汽缸压力不足；严重时出现化油器回火，排气管放炮现象，应立即更换缸垫。
1、缸垫烧蚀故障现象
　　⑴缸垫的两缸缸沿之间烧损：发动机动力不足，汽车行驶无力，加速性差，取下空滤器，发动机怠速时，进气管口可听见“啪啪”声。
　　⑵缸垫烧损部位与水套孔相通：水箱出现冒气泡、开锅，排气冒白烟现象。
　　⑶缸垫烧损部位与油道相通：部分机油会窜入缸内烧蚀掉，排气冒蓝烟现象。
　　⑷缸垫烧损部位与外部大气环境相通：发动机动力性差，经济性恶化，并且从垫的破损处发出激烈的噼噼声。
2、缸垫烧蚀原因
　　⑴发动机长时间大负荷下工作，经常产生爆震燃烧，导致缸内局部高温高压而烧蚀缸垫。
　　⑵紧固缸盖螺栓时，没有按规定要求进行操作，扭力不均致使缸垫没有平整地帖在缸体与缸盖的接合面上导致窜气。
　　⑶点火提前角或喷油提前角过大，使之循环最高压力、最高温度过高。
　　⑷缸垫质量较差、厚薄不均；包口内存有气泡，石棉铺设不均或包边不紧。
　　⑸缸盖翘曲变形，缸体平面不平度超差，个别缸盖螺栓松动，导致密封不严。
　　⑹驾驶操作方法不当，习惯猛加油门和急加速、高速运行，过大的压力加剧缸垫冲蚀。
3、缸垫烧蚀诊断
　　使用中除了通过检测汽缸压力判断缸垫是否烧蚀外，还可取下水箱盖，启动发动机中速运转，观察水箱内有无气泡冒出。若发现水箱加水口不断有气泡冒出，为之缸垫烧蚀。或其水面波动随发动机转速提高而加剧，同时有水喷出，则为汽缸垫水道周围部分冲毁。这时可逐缸断火查出不工作的汽缸，拆下火花塞电极检查是否有水珠；启动发动机，观察是否有水或水蒸汽从火花塞孔喷出，即可确定缸垫是否烧损。
发动机工作时，用手沿缸垫四周移动，若感觉到有气体冲手为之烧蚀。当缸垫损坏严重时，可在缸盖与缸体接合处有气泡冒出为缸垫密封失效。
使用中当发现水箱中水位下降较快，拔出机油尺检查发现机油中有水（机油颜色发黄甚至发白），为之缸垫漏水；另外水箱中冷却水温度上升太快，经常开锅，加水口翻水花，而进水管无凹瘪现象，冷却水无明显消耗，为缸垫漏气，遇上述现象应予更换新缸垫。
4、缸垫途中烧蚀急救措施
　　行车途中发现缸垫烧损，又无备件时可采取以下急救措施：缸垫拆下来认真检查，若是冲坏一道小口，可用烟盒内包装锡纸、废容电器内锡铂或石棉线等物填补在冲坏处，并仔细敲平压实即可；若冲坏面较大时，可用干牛皮垫或从废缸垫相同部位剪下一块贴补代用，车辆回场后重新按技术规范修复。
5、缸垫的使用维护
　　使用中，缸垫应在高温高压气体作用下，有足够的强度，不易损坏：还要具有耐热、耐腐蚀特性；有一定弹性，能补偿接合面的平面度，具有良好的密封性；拆装方便不粘缸及使用寿命长。目前广泛使用的是石棉缸垫，其结构为石棉中间夹有金属丝，水孔周围用铜皮镶边，燃烧室孔铜皮镶包，以防高温烧蚀。装用维护时须注意以下事项：
　　⑴拆卸缸盖螺栓更换缸垫，必须在发动机完全冷却之后进行，以免缸盖挠曲变形。
　　⑵检查缸垫表面有无凹陷、凸起、破损等；检查缸盖和缸体平面度是否符合要求，然后将缸垫、缸盖和缸体清洗干净，用高压空气吹干，以免脏物影响密封。
　　⑶选用的缸垫必须是符合要求（规格型号）质量可靠的原厂配件，安装注意其上下朝向标记，以防装反，避免人为故障。
　　⑷按技术规范拧紧缸盖螺栓（见表1），由于中央向两头对称扩展交叉进行，分2～4次拧至规定的扭力；再在热车状态下紧固一次更为可靠。
　　⑸缸盖螺栓锈蚀拆不下来，千万不要用铁器硬撬，以免损坏缸盖，可往缸盖螺孔中注煤油浸泡片刻，即可顺利拆下。
　　⑹缸盖保管不妥、拆装不慎、缸垫破损变形，安装时清洗不净将导致工作不良、密封不严而造成人为故障必须引起重视。
车辆水温升高的原因
　　认为清洗水箱或拆掉节温器就可以有效的控制车辆的水温。其实并不是那麽简单。车辆水温升高的原因很多，如：
1．水循环系统的故障。冷却液经过水泵、节温器、水箱、缸体和水道，在发动机系统内流动，其中有任何一个环节积垢过多或堵塞，都会引起循环不充分而造成水温升高。此外因漏水儿造成的冷却水量不足，也会导致水温升高。
2．散热系统的故障。失控风扇转动的电机有直动式、电动式、硅油离合式和液压式几种，其中后三种的冷却风量是由温控装置控制的，如控制或执行装置失灵，风量就达不到要求，使水温升高。
3．发动机的故障。如出现爆震、点火时间迟、空然混合比不正确、早燃、冲气缸垫等，都会引起水温升高。
　　为解决水温升高的问题，把节温器拆掉，这是绝对错误的。没有节温器的车辆有部分高温水直接进入缸体，造成发动机水温高，而仪表板未能反映，这样极易给车辆造成重大损坏。没有节温器的车辆还会出现以下问题：
1．热车时间长。
2．正常行驶时，水温变化大。
3．在大负荷时，水温极易升高。

补充一下，看红字，
NAC MG7 1.8T
    Test date 28 April 2007 Price as tested TBA
   
   
What is it?
    This is the Nanjing MG7, one of two new ChinesE-Pro(参数|询价)duced versions of the cars previously known as the MG ZT and Rover 75. The other is the Roewe 750.
    The MG7 is built in China using a production line shipped over from Longbridge in the UK. It's been updated for the Chinese market, too, and fitted with revised versions of the K-series engine (now Euro4 emissions-compliant, apparently more durable and called N-series).
   
What's it like?
    Reassuringly British. This is the same supple suspension, and these the same cossetting bucket seats we tried for the first time on the roads of Britain back in the middle of 1998. The car’s manufacturing centre might have moved 8000 miles east and the people building it might be different in almost every way from the Cowley lineworkers who started it off, but this car is still close to the good old Rover 75/MG ZT in look, feel, image and quality.
    NAC MG engineers have improved the MGZT without changing it much. The car has better-looking rear LED tail lights and new-** alloy wheels. The audio and heating/air conditioning systems are both updated, and there’s a better sunroof assembly. As a result of a Lotus Engineering development programme, the engine range (now comprising a 1.8 160bhp petrol turbo and a 190bhp 2.5-litre petrol V6) can meet Euro4 emissions standards. It also gets a five-layer head gasket aimed at correcting the old K-series engine’s best-known head-sealing fault. For now there’s no diesel for the MG7.
    Nanjing’s new flagship comes in two wheelbases (MG7 and MG7L) and two equipment levels, Sport and Classic, which are distinguished by different bumpers and the fact that the Sport has a mesh grille while the Classic sticks to slats.
    The Sport also gets stiffer suspension rates, though a European driver might not recognise them as such because every Shanghai auto executive you meet tells that that Chinese buyers like ‘relaxed’ suspension rates.
    MG7 sales are just beginning in China (the first car is less than four weeks old) and NAC is still rather reluctant to reveal its domestic pricing. However, four-cylinder models seem to start around £14,000 with the top-spec V6 reaching upwards of £20,000.
    Chinese buyers love ‘toys’, so MG7s come with rear-facing parking cameras and you can also get a neat, twin-screen DVD system for the rear.
    Best of all, the MG7 has been refitted with the NVH (noise, vibration, harshness) package that was removed, along with some cabin fittings, during a cost-cutting exercise called Project Drive in the darkest MG Rover days.
    We're trying a freshly built MG7 1.8T. It’s several years since I’ve driven a four-cylinder MG ZT, but this car seems notably quieter. The restored NVH pack helps, but the car’s inherent mechanical refinement, always one of its best characteristics, still compares well with class leaders. The steering seems a little heavier around the straight-ahead than I remember, but it still has that fluidity that distinguishes BMW designs.
    The ride is flat and well damped even with five passengers and luggage. The engine feels strong, the gearbox gate is well defined and the whole car retains that sub-Bentley feeling of durable luxury that made the 75 a good car. To my cursory inspection, the MG7’s build quality looks fine, too.
   
Should I buy one?
    If you live in China, yes. But while there are plans to restart production of the MG7 on the line that remains at Longbridge, it's unlikely to happen for a year or two, so British buyers won't get the chance.
   
Steve Cropley