Exhaust manifold is an important pars of automotive engine. It is exposed to high thermal load, and its working temperature is usually cycling between low and high, making it prone to failure. During an 800 hour cyclic endurance test of a turbo engine, the NO. 1 bolt on the exhaust manifold has fracture. By analyzing the bolt fracture spot and exhaust manifold bolt holes indenta- tion, it is proposed that the exhaust manifold deformed under thermal load and sheared the bolt as a result. In the paper, this assumption is verified through simulation analysis of the exhaust manifold deformation under thermal load. Based on that, a solution is proposed by increasing the bolt hole diameter so as to increase the bolt and bolt hole initial clearance. In the end, the effectiveness of this solution is verified by testing.