Differences between 87 and 89 M20 motors?

[bmwpower]

I know the water pump is different and the hose routing, but is there anything else?

[mikegar]

which m20 motor? i think the blocks are the same its just the variants that are different. such as m20b25 and the m20b27 are different, and the 87 and 88 m20b27 are different.

[bmwpower]

which m20 motor? i think the blocks are the same its just the variants that are different. such as m20b25 and the m20b27 are different, and the 87 and 88 m20b27 are different.

Sorry, specifically the 87 325i and 89 325i engines. So I guess those would be m20b25.

[jlevie]

The water pump, injector rail, and engine harness differ between an 87 and 89 M20B25. You can use either engine by swapping parts from one to the other. You can use the harness from the wrong year, but depending on which way you are going the alterations required vary. The easiest is using a late model harness in an early model car. There it is only necessary to provide wiring for the tach and start signal.

[bmwpower]

The water pump, injector rail, and engine harness differ between an 87 and 98 M20B25. You can use either engine by swapping parts from one to the other. You can use the harness from the wrong year, but depending on which way you are going the alterations required vary. The easiest is using a late model harness in an early model car. There it is only necessary to provide wiring for the tach and start signal.

Thanks....Is the coolant hose arrangement at the thermostat housing different?

[StereoInstaller1]

Thanks....Is the coolant hose arrangement at the thermostat housing different?

yes

[MR 325]

Motors themselves are exactly the same though, fyi.

[E30_fiend]

The coolant reservoir is in a different location and the radiators are different I believe. The hoses route differently from the radiator.

[SpecM]

and the only difference in the fuel rail is the location of the feed line, but they are completly interchangeable

[sandlock]

what if any are issues using a 87 m20 in a 89 using the late harness and ecu? I noticed my original 89' harness has two extra pins compared to the 87 harness. I believe more was routed through the ecu in later cars than the early. If the motors are interchangeable, should i be swapping the original harness onto the older motor along with the coolant/fuel rail stuff and running my original ecu with it to save hassle since the motors are the same?

[StereoInstaller1]

Motors themselves are exactly the same though, fyi.

They are NOT the same block. The '89 and newer has different motor mount bosses, but that won't change anything on an E30.

[jlevie]

what if any are issues using a 87 m20 in a 89 using the late harness and ecu? I noticed my original 89' harness has two extra pins compared to the 87 harness. I believe more was routed through the ecu in later cars than the early. If the motors are interchangeable, should i be swapping the original harness onto the older motor along with the coolant/fuel rail stuff and running my original ecu with it to save hassle since the motors are the same?

Use the harness, fuel rail, and coolant system stuff from the 89. It would be best to install a new timing belt, tensioner, and water pump.

[StereoInstaller1]

and of course that means tiny bit of fabrication on the late model radiator, NBD.

[sandlock]

Thanks jlevie, that's exactly what I deduced. I'll look into the new waterpump, but the new belt and tensioner have been covered.

[bernzpeed]

i did a swap on mine. i have an 87 325i donor car and an 89 325i. i took the 87 and put it in my 89. the hoses for the oil cooler used were from the 87 since the one from the 89 didn't work. some other parts were used as well.