LIMITED WAIVER

Exhibit 10.37

LIMITED WAIVER

This LIMITED WAIVER (this “Waiver”), dated March 28, 2006, by and among LASALLE BUSINESS CREDIT, LLC, a Delaware limited liability company (“LaSalle”), with its principal office at 135 South LaSalle Street, Chicago, Illinois 60603, the financial institutions that, from time to time, become a party to the Loan Agreement (hereinafter defined) (such financial institutions, collectively, the “Lenders” and each individually, a “Lender”), LaSalle as agent for the Lenders (in such capacity, the “Agent”), and IMPCO TECHNOLOGIES, INC., a Delaware corporation, with its principal office at 16804 Gridley Place, Cerritos, California 90703 (the “Borrower”).

WHEREAS, the Borrower and LaSalle as a Lender and the Agent, are parties to a Loan and Security Agreement dated as of July 18, 2003 (as amended, restated, supplemented, or otherwise modified from time to time, the “Loan Agreement”), pursuant to which the Lenders have agreed, upon satisfaction of certain conditions, to make Revolving Advances and other financial accommodations to the Borrower.

WHEREAS, the Borrower has advised the Lenders and the Agent that it was not in compliance with the Loan Agreement for the fiscal quarter ending December 31, 2005 in the following respects (collectively, the “Financial Covenant Non-Compliance”): (a) Paragraph 14(p)(v) (Maximum Intercompany Accounts), (b) Paragraph 14(p)(vi) (Consolidated Minimum Pre-Tax Income), (c) Paragraph 14(x)(i) (Tangible Net Worth U.S. Consolidated) and (d) Paragraph 14(x)(v) (U.S. Minimum Pre-Tax Income). The Financial Covenant Non-Compliance constitute or more Events of Default (collectively “Financial Covenant Defaults”).

WHEREAS, the Borrower has requested that the Lenders and the Agent agree to waive the Financial Covenant Non-Compliance and Financial Covenant Defaults, and the Lenders and the Agent are willing to agree to such waiver on the terms and subject to the conditions hereinafter set forth.

NOW THEREFORE, the parties hereto agree as follows:

1. Waiver.

(a) Effective as of the Effective Date, the Lenders and the Agent hereby waive the Financial Covenant Non-Compliance and Financial Covenant Defaults.

(b) The waiver granted in Section 1(a) above is a one-time waiver, given solely for the specific covenants and specific time periods set forth herein. Nothing contained in this Waiver constitutes a waiver by the Lenders or the Agent of any other term or provision of the Loan Agreement or the Other Documents, whether or not the Lenders or the Agent have any knowledge thereof, nor may anything contained in this Waiver be deemed a waiver by the Lenders or the Agent of any non-compliance with the terms or provisions of the Loan Agreement or the Other Agreements that may occur after the date of this Waiver. Without limiting the foregoing, a future non-compliance with any of the financial covenants described in the second “Whereas” clause above will be a new Event of Default.

2. Waiver Fee. In consideration for the waiver granted by the Agent herein and in addition to all other fees and costs, the Borrower hereby agrees to pay to the Agent a nonrefundable fee equal to Five Thousand Dollars ($5,000), which fee will be fully earned, due, and payable as of the date of this Waiver (the “Waiver Fee”).

3. Representations and Warranties. The Borrower hereby represents and warrants to the Lenders and the Agent, that:

(a) Each of the representations and warranties set forth in Paragraph 13 of the Loan Agreement is tr