Warm-up regulator – sale, repair & purchase (Bosch K-Jetronic)
The Warm-up regulators (control-pressure regulator) of the Bosch K-Jetronic regulates the control pressure and thus the fuel-air mixture: when the engine is cold, it enriches the mixture, and as the temperature rises it leans it out to operating values. If the diaphragm ages or the internals gum up, the engine runs poorly – especially in the warm-up phase. Since Bosch no longer supplies new warm-up regulators, overhaul and tested used parts are the way to go today. With us you get both – and we pay you for defective regulators.
Buy an overhauled warm-up regulator
Tested Bosch warm-up regulators from stock – ready to ship, with invoice. Stock changes constantly; we are happy to check your part number.
Browse selectionHave your regulator repaired
Complete overhaul: new diaphragm & seals, new heating resistor if needed, housing refurbished like new, function test. Return shipping included (DE), 12 months' statutory warranty. Your genuine part is retained.
Book repairSell a defective regulator
or 100 € as a shop voucher
We buy every complete defective Bosch warm-up regulator – hassle-free by e-mail or phone.
Go to buybackHow can you tell a warm-up regulator is defective?
Typical symptoms of a defective warm-up regulator are:
- Poor cold start or stalling shortly after starting
- Jerking, surging or rough idle in the warm-up phase (first 5–10 minutes)
- Poor throttle response and noticeable lack of power
- Significantly increased fuel consumption (mixture permanently too rich)
- Problems with hot starting
- During testing: incorrect control pressure cold and/or warm
Certainty comes from measuring the control pressure with a pressure gauge between the fuel distributor and the warm-up regulator – the values must match the Bosch specifications for your regulator number. Common causes inside: aged or cracked diaphragm, clogged screens, corroded internals, defective heating coil.
Repair & overhaul – how it works
We overhaul both designs completely: warm-up regulators without vacuum and with vacuum (vacuum connection) – on vacuum regulators the vacuum diaphragm is always replaced as well.
- Book repair – directly online in the shop or by phone. You will receive the address to send it to with your order confirmation.
- Remove and send in the regulator – two fuel lines, connector, two screws. Packed well and sent to us as a parcel.
- Overhaul with us – disassembly, cleaning and refurbishing of the surface (the housing looks like new again), new diaphragm and seals (brand-name repair kit), new vacuum diaphragm on vacuum regulators, new heating resistor if necessary – then reassembly and function test. Processing usually takes just a few business days.
- Return shipping included – install it and enjoy the cold-running phase. With 12 months' statutory warranty.
Buyback: 50 € for your defective warm-up regulator
Do you have a defective warm-up regulator left over – from a donor car, a parts box or after a conversion? We pay a flat 50 € per pc for every complete Bosch warm-up regulator (0 438 140 …), regardless of condition. It's that simple:
- Register your regulator online or give us a quick call: +49 179 8991069
- You will receive our confirmation and shipping address by e-mail (postage is paid by the sender)
- Payout after receipt: 50 € by bank transfer or PayPal – or 100 € as a shop voucher
Are you buying a refurbished regulator from us right now? Then you get the 50 € as an old-part bonus refund.
Which vehicles? All Bosch K-Jetronic
We overhaul, buy and sell all warm-up regulators with a Bosch number 0 438 140 … – regardless of vehicle make. Typical vehicles with K-Jetronic:
| Mercedes-Benz | R107/W107 (280–500 SL/SLC), W116, W123 (230 E, 280 E), W126 (280–500), 280 models with M110, V8 M116/M117, 280 GE (W460) |
|---|---|
| Porsche | 911 (2.7, SC, Carrera 3.0), 930 Turbo, 924, 928 |
| VW / Audi | Golf I GTI, Scirocco, Jetta • Audi 100/200 5-cylinder, Urquattro |
| Others | Volvo 240/260, Saab 99/900 Turbo, Ferrari 308i/Mondial, DeLorean DMC-12 and many more |
Why KFZTeile-Thot?
- Specialized in classic Mercedes and the Bosch K-Jetronic – parts trade and workshop practice from a single source
- Over 1,000 positive reviews from our eBay sales
- Like-new look included: The housing surface is refurbished with every overhaul
- Fixed price, clear service: 400 € incl. return shipping, 12 months' statutory warranty – no surprises
- Fast turnaround: Usually processed within a few business days
FAQ about the warm-up regulator
What does the warm-up regulator do in the K-Jetronic?
It regulates the control pressure acting on the control plunger of the fuel distributor and thereby determines the mixture composition. When the engine is cold, it lowers the control pressure – the mixture is enriched (cold-running enrichment). As engine temperature rises, the control pressure increases and the mixture leans out to operating values. Variants with a vacuum connection additionally enrich at full load.
What symptoms does a defective warm-up regulator have?
Poor cold starting, stalling after starting, jerking and rough running in the warm-up phase, poor throttle response, increased consumption and hot-start problems. Measuring the control pressure gives a clear answer: if the values, cold or warm, deviate from the Bosch specifications, the regulator needs to be overhauled.
What does the warm-up regulator repair cost and what is included?
400 € fixed price including return shipping within Germany and 12 months' statutory warranty. Included are disassembly, cleaning, refurbishing of the housing surface (like-new look), new diaphragm and seals (brand-name repair kit), a new vacuum diaphragm on vacuum regulators, a new heating resistor if necessary, and the function test.
Do you also overhaul warm-up regulators with vacuum (vacuum capsule)?
Yes, we completely overhaul both designs – warm-up regulators without vacuum and with vacuum. On vacuum regulators the vacuum diaphragm is always replaced as well, and a defective heating resistor is replaced if necessary.
How long does the repair take?
Usually a few business days from receipt of your regulator. We confirm the exact timeframe when we receive your order.
Why repair instead of a replacement regulator?
Bosch no longer supplies new warm-up regulators. With an overhaul, your genuine part with the part number matching your vehicle is retained – a plus for originality and value retention. In addition, there is no core deposit and no risk of an unknown replacement part.
Which vehicles do you offer repair and buyback for?
For all Bosch warm-up regulators with part number 0 438 140 … – including Mercedes R107, W116, W123, W126, Porsche 911 SC/930/924/928, VW Golf I GTI, Audi 100/200/Urquattro, Volvo, Saab, Ferrari and DeLorean.
Does the KE-Jetronic also have a warm-up regulator?
No. On the KE-Jetronic, the electro-hydraulic pressure actuator handles the mixture adjustment – a warm-up regulator exists only on the K-Jetronic (incl. K-Jetronic with lambda control). If you have problems with the KE-Jetronic, feel free to contact us anyway.
How does the buyback of defective warm-up regulators work?
Register the regulator on our buyback page or call us. You will immediately receive confirmation and the shipping address. After receipt, we pay out 50 € per complete regulator by bank transfer or PayPal – or 100 € as a shop voucher.
Can I repair the warm-up regulator myself?
Repair kits are available, and the assembly itself is doable for experienced DIY mechanics. Without control-pressure measuring equipment and experience, however, it remains flying blind: a regulator that works incorrectly leads to poor running and increased fuel consumption. That is why our overhaul always includes the function test.
Direct line
Phone: +49 179 8991069 (Mon–Fri 8 am–6 pm)
E-mail: thot.kfzteile@gmail.com
Or use our contact form – we will get back to you as soon as possible.