Hot Head - Transmission Digest

Hot Head

A 2000 Mercury Grand Marquis with a 4.6L engine using a 4R70W transmission is at a general-repair shop for weeks. The problem is an intermittent engine surge on top of the 1-2 shift when hot. The perception is an engine problem. Eventually, the idea of the converter clutch coming on was being considered. Without much testing, the valve body and solenoids were replaced yet the problem persisted.

Hot Head

Shift Pointers

Author: Wayne Colonna
Subject Matter: 4R70W Transmission
Issue: Cylinder head temperature

Shift Pointers

  • Author: Wayne Colonna
  • Subject Matter: 4R70W Transmission
  • Issue: Cylinder head temperature

A 2000 Mercury Grand Marquis with a 4.6L engine using a 4R70W transmission is at a general-repair shop for weeks. The problem is an intermittent engine surge on top of the 1-2 shift when hot. The perception is an engine problem. Eventually, the idea of the converter clutch coming on was being considered. Without much testing, the valve body and solenoids were replaced yet the problem persisted.

This shop had no knowledge of an ATSG bulletin that covers a similar problem. The bulletin speaks of the converter clutch applying on top of the 1-2 shift due to a deteriorated No. 7 check ball. The difference is the deteriorated No. 7 check ball causes the problem to occur on every 1-2 shift, cold or hot. The general-repair shop was fighting an intermittent 1-2 surge problem when hot. And it continued to have the same problem after changing the valve body and solenoids. After much frustration, he sent the vehicle to a local transmission shop to look into the problem.

Lorenzo Ortiz from Phillips Transmissions was the lucky one to receive this vehicle. After road testing the vehicle to experience the problem, it did indeed feel like the converter clutch was applying on the 1-2 shift. His first approach was to monitor the solenoid command with a scan tool and a volt meter. By doing this, he confirmed that the computer was indeed commanding the clutch to apply. The question now is why. With shift scheduling operating properly, engine load and vehicle speed could not be the problem. This narrowed the search down to temperature. The engine temperature and transmission fluid temperature were looked at and were text book perfect.

But Lorenzo noticed how the fans were running at full speed. He then looked at the cylinder head temperature (CHT) sensor and it was running at 262°F. He popped open the hood and ran the engine idle up to about 2,000 rpms for more than 30 seconds and watched the cylinder-head temp drop to almost engine-coolant temp.

Once the temperature dropped, the fans started to run normally and the converter clutch no longer applied on the 1-2 shift. As he drove the vehicle, the cylinder head was quite lethargic in increasing in temperature.
But with continued driving, the problem suddenly returned. Looking at the cylinder head temperature, he saw 251°F. Once again, by increasing engine rpms in park, the temperature would drop immediately. This confirmed that a flow problem existed with the engine coolant, causing a hot head. It also confirmed that the CHT sensor influences a converter clutch apply strategy that is not mentioned by Ford with this particular vehicle. It does state the following:

If the CHT exceeds about 121°C (250°F), the powertrain control module disables four fuel injectors at a time. The powertrain control module will alternate which fuel injectors are disabled every 32 engine cycles. The four cylinders that are not being fuel injected act as air pumps to aid in cooling the engine.

If the temperature exceeds about 166°C (330.8 F), the powertrain control module disables all of the fuel injectors until the engine temperature drops below approximately 154°C (309.2°F).

Since the engine coolant temperature was functioning normally, a defective water pump is not suspected. A restricted water jacket seemed more likely, which may be remedied with a flush. Lorenzo immediately returned the vehicle to the general-repair facility for them to resolve the flow problem as he heard the owner had a hot head waiting for his car.

You May Also Like

Sherlock Holmes Approach to an AB60 No-Move Situation

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult.  Using scopes provides

ab60

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult. 

GM 6T40 Pump Identification Guide

The 6T40 was introduced in 2008 for General Motors front-wheel-drive cars in the Chevrolet Malibu and has gone through several changes throughout its three generations, specifically in the pump area. The 6T40 is closely related to the more lightweight 6T30 and the heavier duty 6T45 and 6T50. Generation one started phasing out during the 2012

Seeing the Forest AND the Trees

They say that the proverbial phrase “I couldn’t see the forest for the trees” means that a person or organization cannot see the big picture because it focuses too much on the details. Related Articles – 4L60E Harsh 1-2 Shift – TASC Force Tips: Diagnosing 8L45 & 8L90 Shift Complaints – TASC Force Tips: Hydraulics

The Manifold Pipeway

The Honda six-speed transmission has been on the bench of many specialty shops for one reason or another (figure 1). But, for those of you who have yet to lay your hands on one, mounted on the upper side of the unit is one of the largest, if not the largest solenoid and pressure switch

8L90 Vacuum Testing

Below are the diagrams for vacuum testing GM 8L90 transmissions. Note: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow. Springs are not shown for visual clarity. A low vacuum reading indicates wear. For specific vacuum test information, refer

Other Posts

Shift Pointers: What to do when the 62TE TRS tab breaks

How frustrating it is when on a hot summer day, as you go to open a nice cold can of your drink of choice, and the tab breaks off? You are outside, away from any tools to remedy the problem quickly. It now requires a MacGyver mentality looking around at the resources available to get

Shift Pointers: Failures caused by incorrect tire sizes

For years ATSG has produced a wide range of issues related to improper tire sizes on vehicles. Even under-inflated tires have been known to cause issues. Problems such as premature failure with an active 4WD transfer case will occur with incorrect tire sizes. Related Articles – 10L80 and 10R80 pump gear differences – Top 20

Shift-Pointers-Jan-Figure-1-1400
Shift Pointers: Focused DTCs

On occasions when a vehicle’s computer system detects an error, it can set an array of diagnostic trouble codes. The variety and quantity of them require the ability to diagnose diagnostic codes, so it’s nice when codes set that point directly to the problem.  Related Articles – Going the extra mile: Proving your transmission repair suspicions

Shift pointers: High-mileage transmissions and the aches and pains of age

Among the most common four speed-transmissions keeping shops busy today are the Ford 4R70E/W, the GM 4L60-E and the GM 4L80-E. In most cases, this typically equates to working on high-mileage vehicles. Aches and pains come with age and/or high mileage. In fact, when we see a person who looks beat and tattered, some may

Shift-Pointers-November