I recently had a cracked head replaced on my 97 z3. It ran fine for about a month. Now it is running hot again. Any idea what it may be.
only took off the thermostat, but put it back because of the price of a new one. Kinda pricey to not be sure that was the problem
Hello,In what circumstances does the vehicle overheat? All the time, only at idle, only while driving?Thank you.
It overheats while driving mainly. Although after idleing a while it will gradually overheat. I must add, the heater is not heating either, indicating it may be the thermostat. Not noticing the fan coming on either, is there a fuse that controls the fan.... I guess I'm just being overcautious because of a previously cracked head. Fan comes on but does not heat...
You can never be over cautious with an over heating engine. It can lead to warpage of the block which means and engine or other damage due to heat transfer.
If the water pump has not been removed it would be a good idea to remove it and inspect the impeller. Also keep an eye on coolant level. To find out if this is the thermostat you can boil it in a pot on the stove and see if it is opening. The usual course in a shop is to start with both a thermostat and water pump if no external leaks can be found. But with the head being done only a month ago this may be a problem with the new head gasket. If you had the work done at a dealer or a shop this still may be under warranty. Keep in mind if the engine over heats too much they may void the warranty as negligence so it may be in your best interest to give them a call soon. This engine I believe also has the mechanical fan attached to the water pump. This is responsible for engine cooling. The electrical fan is a pusher fan for the AC system and may not come on even during an over heat. The mechanical fan has a fan clutch that is a viscous clutch (fluid filled) if it has leaked out it may not be engaging properly. To check this usually you can see a lot of dirt on the backside of the metal center portion of the fan (toward the engine).
Hopefully this will just prove to be something simple like a thermostat or water pump. For the heat inside the vehicle it may be a clog due to the last over heat as coolant can solidify in high temperatures but it may be related to poor circulation. If the thermostat does not open or the water pump impeller is failing then poor circulation can result in both symptoms.
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I wish you the best.
Roger, actually the work was done over a year ago. So the warranty is out on new block. I have just had the car parked. The overheating I noticed did happen about a month after the new block. Sorry didn't explain that well. I did put the thermostat in a pan of boiling water, but the type thermostat it is you cant tell if it is opening or not. Does that make sense? It is held in place with some type of arm you put it on???? I will definitly check the waterpump, but I thought if it was something as simple as a thermostat I would start there. This particular thermostat is about 80 bucks. Perhaps I can find a cheaper replacement thermostat.
Thank you for the update. One the flip side, if the work was done at the dealer or if the shop you used, used parts from the dealership, BMW will cover any failure of the components used for up to two years unlimited miles. This is the benefit of spending a bit more money on a part from the dealership. It is worth the two year warranty on both parts and labor even if another shop did the work if that component has failed.
You should be able to see the thermostat metal portion arm move a bit when boiled but you are correct it can be hard to see but fluid should flow through it so this would be a way to check it as well. Fluid will not flow closed but it will hot and open so this can be another way to test this :)
You can try pelican parts as well. They seem to have some good pricing.
I hope this helps!
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10 Years Dealer Experience, Shop Foreman