Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   Pelican Parts Forums > BMW Forums > BMW Technical Forums > BMW Z3/Z4 Forum

LinkBack Thread Tools Rating: Thread Rating: 4 votes, 5.00 average.
Thread Post New Thread    Reply
Registered User
Join Date: Apr 2003
Location: Colorado Springs Co
Posts: 147
Over heating

My 1998 Z3 1.9 overheats after about 10 miles of driving.
After checking the reservoir, it's empty.
I loosened the radiator cap and the bleed screw and the reservoir fills up. After a few minutes of sitting to cool down a bit. I will run fine.
Is this thermostat stuck closed?
Thanks for any help.
Old 06-24-2009, 01:30 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
Schneller's Avatar
Join Date: Aug 2002
Location: Newbury,MA USA
Posts: 259
Overheating problems fall into 2 general categories:

1) Lack of Coolant flow as a result of:
  • Faulty water pump not circulating coolant (w/ engine cold & expansion tank cap off & engine running, a small stream of water can be observed spilling back into the tank from a return attached to the filler neck. No flow? blip the throttle to see if it appears, still no flow? need to investigate further, but water pump is suspect)
  • Low or no coolant to circulate
  • Obstructions, ie clogged radiator (resulting in reduced heat liberation capacity. IR thermometer scan of individual coolant tubes will show uneven temp readings across tubes, ie. hot until clog is reached, then much cooler),
  • Obstruction due to stuck T-Stat (If T-Stat is stuck closed, the lower radiator hose never gets hot to the touch as it's not letting coolant pass through the radiator to be cooled. Hence the coolant stuck in the radiator & lower radiator hose stay cold while the engine overheats.)
  • Obstruction by Exhaust gases from a faulty head gasket w/in the block or head. (Oftentimes building pressure within the block forces coolant back into the expansion tank where the cap releases the pressure & coolant into the overflow hose & out of the system).

2) Lack of air flow over radiator as a result of:
  • Dirt & debris obstructing flow through radiator core. (Heat can't be liberated)
  • Engine fan clutch not engaging at low speeds to pull air through radiator. (Again heat can't be liberated)

You may have a combination of these problems conspiring to produce your overheating situation. If you're not capable, you should have someone knowledgeable evaluate the cooling system for you. It's a serious situation that if not handled properly or in a timely manner will result in some very expensive engine repairs.

A BMW dealer can offer help as can any one of the capable independent BMW repair shops listed at

Hope this helps, Good Luck!
Mike Morris
Schneller BMW Performance
26 Middle Rd Unit 1-2
Newbury, MA 01951
Old 07-06-2009, 04:39 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)

Thread Tools
Rate This Thread
Rate This Thread:


All times are GMT -8. The time now is 08:21 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.