DeLorean Dirty Dozen and More

Peter Naulls
14 min readMay 20, 2022

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For potential buyers and new owners alike, the 12 (and counting) most serious issues on a DeLorean.

Introduction

Any comprehensive guide about DeLorean issues would be extraordinary lengthy. Instead, this is meant to be a reference for newcomers evaluating a car — especially in the case of a car you might be planning to purchase, or in one you’ve just obtained. Some of the items here may be problematic to check just from photos, and might not be obvious until you can spend some up close time with the car.

The DeLorean is often panned as “unreliable” by those not in the know. The truth is that a well-maintained car — and in particular addressing the items mentioned here — can be extremely reliable. Many cars take long distance trips or are daily drivers.

There are multiple solutions to the following, and multiple vendors — this guide will only touch upon some possible paths.

The List

0a. DeLorean Facts

Not part of the list, but an import precursor:

  • Best count of the number of cars made is 8975 — http://www.citizenkidd.com/dmc/pages/vin.aspx. A lower bound on the number of cars remaining today in 2023 (based upon typical attrition rates) is 4500. Exactly 1/3 of cars were automatic.
  • There were rolling changes made all through production, so there are no “1981 models”. Cars were made in 1981 and 1982. Cars with a 1983 VIN were made in previous years. More important is the month of production; in particular, cars made in late 1981 are far more similar to cars made in 1981 than they are to “early VIN” cars made in early 1981. Ultimately though, more than 40 years on, present condition is most important.
  • The top speed of the cars is generally around 120 MPH — the 85 MPH speedometer was a federal mandate at the time.
  • The cars are not “heavy” as often stated. The weight is 2700–2800 lbs, which was very typical at the time. Modern cars are usually much heavier. The construction is mild steel double wishbone frame, fiberglass body and relatively thin stainless steel panels, with rear mounted engine.
  • The recommended purchase price for a mechanically sorted car is in 2023 is US$55,000. In general, lower priced cars will end up costing you just as much or more.

0b. Parts Vendors

In approximate order of parts availability:

And now, the main event:

1. Frame, frame, frame

It is a rare DeLorean indeed that has no rust whatsoever, and certainly the original mild steel frame is prone to rust, especially in cars from colder climates. Unless the car has had a recent frame off restoration, frame replacement, etc, some rust is almost certain on the car and frame in particular.

Any advanced rust will be immediately obvious by looking the front frame extension, engine cradle and fuel tank closing plate. In very advanced cases, the treatment is to do a frame off and repair or replace with another frame — either an original, or (very expensive) stainless offering from some of the vendors.

In mild cases, treatment with POR-15 etc on the car is entirely practical. The epoxy lifting is also very common, and should be removed if possible so the surface can be fully accessed.

There are a number of spots of note that might not be immediately visible without removing wheels, or use of a flash light and are almost never consider in sale photos:

  • Inside the engine cradle extensions — these are hard to reach or even see in. Internal frame treatment is possible here though.
  • In the cross member under the cradle extensions — this doesn’t always have epoxy all the way through, and even when it does, it may be lifting.
Rust in the rear support under the engine cradle.
  • Inside the front frame extension — again seeing in here is tricky, and requires getting under the frame with a flashlight, and is hard to reach with the steering rack in the way.
  • Other spots like the sidewall where the fuel filter mounts — this is somewhat thin and can collect moisture.

Also don’t forget to remove the fuel tank closing plate and examine its inside, as well as the frame sections it’s covering.

2. Fuel lines

The original rubber fuel lines after 40+ years are aging badly, and prone to split and are a severe fire risk at worst, or at the least, leaving you stranded.

Even lines that were replaced in the last 20 years before braided options were available should be also replaced — these have been known to fail prematurely.

The are a total of 23 lines on a DeLorean (some cars might have one additional if a valve is fitted to the fuel pump lines):

102318 Injector Line #1
102323 Injector Line #2
102327 Injector Line #3
102331 Injector Line #4
102335 Injector Line #5
102339 Injector Line #6
102348 Control Pressure Line
102357 Primary Pressure Line
102370 Cold Start Injector Line
102400 Longer Frequency Valve Line
102395 Shorter Frequency Valve Line
102365 Supply Line
102359 Return Line
106979 Fuel pump feed/return/accumulator (x3)
106997 Accumulator
106983 Fuel feed front
106998 Fuel return front
106989 Fuel feed rear
106995 Fuel return rear
106287 Fuel pickup
106683 Fuel tank vent tube

The final 6 lines listed here are metal and don’t need to be replaced except in severe cases of corrosion, although we’ll talk about the fuel pickup in the pump section. However the clips holding the 5 lines on top of the frame are often broken, but replacing is largely a cosmetic issue, and requires the body to be lifted to reach many of them.

All the vendors offer braided replacement lines (for the first 13 items) , although it can be confusing since the kits offered only have a limited number of the lines, so you need to make sure you get all of them. It can also be worth replacing the elbow fittings — especially the one feeding the fuel filter.

Braided lines installed.
Fuel filter elbow has seen better days.

Regularly overlooked are the 4 shorter lines — 2 from the fuel pump (accessible in the trunk under the cover) and 2 accumulator lines under the center of the car. The original lines have 3 layers — a black plastic/rubber coating, which is often flaking or completely gone, a white fabric/asbestos second layer, and an internal hose, which is typically yellowed and very hard from age. If you are seeing white hoses, it’s well past time to replace. You need to use the correct fuel line clamps here (they should come in a kit from a vendor), not the typical hose clamps.

Cost for all items is about $500.

3. Vacuum lines

This is an easy one, but again often overlooked. The factory original vacuum lines are typically aging and leaking, and are one of the first things to consider when trying to make a car run smoothly, and especially address high idle.

Original aging vacuum lines.

Replacing the full complement of 11 lines can be done for about $45 from vendors. However, getting to everything requires a visit to the valley — see the next section.

4. Valley of Death

This refers to the region on top of the engine, below the intake manifold. It is known for collecting coolant, loose engine parts and tools and other foreign objects.

Accessing the valley is not difficult, but it does mean removing a number of engine components, which can be a bit overwhelming for a new owner.

VoD being cleaned.

A “trip to the valley” is particularly important, because collecting coolant/water can cause block rot. Running through the valley is the heater return pipe, which is known to rust out, but is relatively easy to replace. With that is the Y pipe, which can also corrode, especially its bolt holes into the engine.

And as noted, above, replacing the full set of vacuum hoses requires this — 3 of the hoses terminate in the valley. Also, a tune up (spark plugs, wires, distributor and cap), are easier to access if the intake is removed, but not required.

There’s some debate over whether the valley should be painted (in high temperature engine paint), or just left after cleaning.

5. Roofbox

Like the frame, the original roofbox is mild steel, and prone to rust both inside and out. It is also prone to lifting at the rear — the exact reasons are not clear, but probably due to aging glue and continual flex — in any case, it needs repair by bolting down.

The roofbox is clearly lifting here.

Sometimes it is obvious by looking at the fit of the T-panel on the roof, but can otherwise be examined by removing the finishing plate above the rear window, where any lift will obvious. Over time, not fixed, this can lead to torsion bar failure. A boroscope is suggested also to look inside the roofbox access panel, especially the front area.

The repair is somewhat involved, but kits can be had from vendors for about $40. The repair involves resealing inside and out against further rusting.

In more extreme cases, especially in cars that have been sitting for any length of time, the roofbox will need replacing — this is a very involved repair, and stainless steel replacements are $1600 or more from vendors.

It is almost certain that any DeLorean will need one of these two repairs in the near future if it hasn’t been done, so this is an important thing to know about any given car’s history.

6. Fuel pump

The fuel pump itself tends to be an incremental and obvious failure, although plenty of original factory pumps are still going. There are multiple options for replacement from vendors, or kits to install mainstream ones. Some options include integrated fuel senders, to replace the factory sender, which can deteriorate over time, and even fully working isn’t the most reliable in reporting. Also available is a separate sender MCU to improve this.

However, what can be more concerning is the rubber boot around the pump — this can perish over time, especially with use of fuels with ethanol in them. It’s also worth examining the fuel tank for debris, which can cause havoc with the K-Jet system. Finally, check the fuel pick up line; sometimes it’s missing or jury rigged.

Finally, and very important, as mentioned earlier, the 2 lines here from the fuel pump — these are the easiest of all the fuel lines to replace, so there’s no excuse.

Fuel lines to the fuel pump. These are clearly original, deteriorating lines.

7. Fuse box and Relays

Fuses and relays have been known to melt and cause fires due to high current draw or shorts, so this is important to check regularly. In particular, aging cooling fans can have very large current draw, and updated, much lower draw fans are available from vendors. However, some owners advocate for retaining the original fans (which have higher air flow), and improving the wiring or refurbishing the fans.

Fuse box area with a number of updates.

Dave McKeen sells a number of solid state relays and other items which can significantly reduce the current load (and therefore heat) of many items, and several of these are highly recommend for any car, especially the RPM relay, Lamba relay and also a fan relay to monitor the fans, above:

https://dm-eng.weebly.com/

8. LEDs

Replacing LEDs in the car significantly reduce current draw, which is important to the above. And in particular, the some or the bulbs can get quite warm, especially the one in the engine bay, so putting in LEDs can be important.

There are a couple of drawbacks to installing LEDs, and the battery light in the dash can’t be replaced, however, this guide covers everything apart from the headlights:

One caveat about replacing bulbs in the dash is that sometimes the original flexible PCB does not survive removal of the connectors due to its age. Replacements from vendors can be had for about $40.

7. Tires

This one is obvious, but so often not done. Tires are good for about 6 years, and then should be replaced, whether driven on or not. Sometimes DeLoreans have the factory original Goodyear NCT tires, which are only good for show.

At present in the United States, the only tire brand available that has front and rear matching are Hankook Kinergy, which are available from a number of retailers. Some European owners have found matching Nangkang tires. Since the Hankook tires have only been available for a couple of years, a car fitted with those will be in good condition.

That said, mismatched front/rear tires are not unusual to get the correct sizes, or sometimes the sizes will be varied to get a matching brand.

Front tires are 195/60R14 and rears are 235/60R15.

Hankook tires ready to be fitted.

8. Trailing Arm Bolts

These bolts are part of the rear suspension, and hold the trailing arms to the frame. This was a relatively weak part of the original design of the car, and these bolts over time bend, and eventual break, leading to potentially dangerous situations. A car with original trailing arm bolts will almost certainly need them replaced; vendors sell stronger ones.

On a manual transmission car, this is straightforward, if a bit involved, since it requires a number of steps, and other parts are often replaced in the process, including the trailing arm bushings and mounts.

Original trailing arm bolts after removal. One was so badly bend, it had to be cut out.

On an automatic transmission, the clearances, especially on the driver side, are very tight, and the process can be extremely time consuming, involving either loosening the transmission mounts or removing the trailing arm altogether, and is ideally a two person job with a lift.

9. A/C

Poor air flow from the vents can often by fixed by cleaning out the fan or “hamster cage” or replacing the motor — a full assembly can be had cheaply and is very easy to replace. Over time the motors corrode and may start to squeal.

Hamster cage, ready to be cleaned.

The A/C flap is prone to rust, and is NLA from vendors, but can be reached by removing the glovebox and refurbished.

For the rest of the A/C system, a rebuild of the heater box is sometimes necessary — this is a particularly involved job, as much of the dash has to be removed, the box resealed and broken items on the aging plastic repaired. In addition, typical A/C car items like the compressor and hoses may need to be replaced and the system possibly upgraded.

10. Radio and speakers

The original Craig and ASI radios often are faulty from age, but can be refurbished. It is however also common to fit a new style standard DIN radio (in which case, a new DIN panel needs to be fitted, or the original cut to size), or it’s possible to find modern radios which fit in the original space such as RetroRadio — https://www.retromanufacturing.com/products/1981-83-delorean-retroradio.

DIN-sized faceplate and original-sized faceplate.

One thing of note when updating the headset is that the grounds on the speakers need to be split — the original wiring uses shared grounds to the speakers, which results in awful sound if you do not do this.

The front speakers themselves may be OK, and but are easy enough to replace — one recommendation though is to use brass standoffs to get the screws back in. Rear factory speakers will in almost all cases have suffered rot, and will need to be replaced. Doing so is somewhat involved, since the rear interior panels have to be lifted from the door frame. Replacing the speaker wire is an option here too.

Typical rear speaker condition with dry rot.

11. Seat rails and carpet

This is an easy one, but the seat wells can collect water from the evaporator drain, doors and other locations. This leads to obviously damp carpet, and the seat rails in particular can get rusty. Too far gone, they’ll need to be replaced. Carpet too can be replaced in pieces or as a whole set — also worth checking the rear parts for battery leaks.

Seat rails that have been better days.

12. Steering

The steering bushing is a typical wear item, and is easy and cheap to replace. Sometimes overlooked is the inner steering bushing, which can crack — vendors sell a strong version of this — the steering assembly needs to be removed to fit this.

Steering assembly. Bushing is seen right at the end.

Without this, the steering will be sloppy. Another possible wear item here is the upper universal — over time, the joint may wear, making steering less precise.

13. Grounds, grounds, grounds

Clean ground connections are import to correct electrical behavior of the car. Over time, connections can corrode or oxidize and need to be cleaned.

There have been many discussions on this, but this provides a good diagram for checking all the ground points. One particularly important one is mentioned earlier — the connection to the passenger side trailing bracket.

https://delorean.bnebel.com/tiki-index.php?page=Groundconnections

14. Automatics

The original factory automatic computers aka governors, are well beyond their best before date, with failing components and connections. Vendors will rebuild these for around $400 with a core exchange. Also check the operation of the WoT microswitches (2 on an automatic, 1 on a manual) and cable adjustment — both throttle and governor cables. A poorly adjusted automatic DeLorean does not drive well.

Also make sure automatic transmission filter and fulid is fresh.

15. Manuals

There are two nuts inside the end cap of the transmission housing that are known to have not been properly tightened at the factory. It’s possible to get to these without removing the transmission from the car. Left unchecked, a hole can be drilled in the housing.

This is what can happen. Photo courtesy Mike Guy.
And this is what it should look like.

16. Binnacle and instrument cluster

The binnacle (the fiberglass surround of the instrument cluster) will have its vinyl covering crack with age. This can be repaired yourself, or with a professional kit. Sometimes newly-made ones are available.

The instrument cluster itself has some age concerns:

  • The original trip reset shaft is plastic and prone to breakage. Rebuild parts and instructions are available.
  • The flexible circuit board may work fine until it’s removed (such as performing the above) and then fail, especially the contact pins, when reinserted. New ones can be purchased from vendors.
  • All of the the lights in the cluster can be upgraded to LEDs with the exception of the battery light — this must remain incandescent for correct alternator operation.

17. Brakes

TODO

18. Shift linkages

TODO

19. Fluid Changes

TODO

20. Headliners

TODO

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Peter Naulls

Vegan, IoT, Coffee, Lego and DeLoreans