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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
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Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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Why does Toyota previas have so many head gasket problems

Customer Question

why does Toyota previas have so many head gasket problems
Submitted: 1 year ago.
Category: Toyota
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. The main reason of head gasket issues (not just Toyota, but any manufacturer) is them using an aluminum cylinder head and a cast iron cylinder block. When an engine overheats, the aluminum tends to expand faster than a cast iron cylinder head. When the metal expands, the seal between the head and the block (the head gasket) is damaged. Once the seal is damaged, either you get an internal coolant leak into the cylinders (huge clouds of white smoke) or you get an external coolant leak (drips on the ground). The aluminum heads warping slightly when past normal operating temperature has been a major concern for the manufacturing community for many, many years. When I was with Nissan, we did 2-3 head gaskets a week on trucks, which were quite prone to head gasket issues.

The Previa engine is no different than any other aluminum head engine. Overheat it, ti will distort due to being past normal operating temperature. It then causes the gasket to fail. The gaskets are not the problem. it is the deflection fo the aluminum flat side of the head that faces the head gasket. That is why we have to have them 'machined' after the head gasket fails....this is to restore a perfectly straight surface. Once the head overheats, and warps (we are talking 3-4-5 thousandths of an inch here), and warps, it will not return to a true flat plane. It stays warped.

Expert:  Toyota Service replied 1 year ago.

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