Engine running hot?


Accufab

Well-known member
Mar 14, 2006
142
Some of our customers have experienced the GT engines running hot. This is most prevelent when they are running the car hard, such as in a road racing environment. This problem is related to the engine not getting efficient coolant circulation. We have had several cars on the chassis dyno and noticed an interesting little issue, one that is almost impossible to see except on the dyno or a chassis lift (so you could view it from the underneath). The water pump is so efficient, it creates a partial vacuum causing the radiator hoses to suck closed. This starts at as low as 3500 RPM and by 6000 RPM, the hoses are completley (almost) closed off. No wonder these things are running hot.

John Mihovetz has had some stainless steel springs made, springs that are the exact inside diameter of the hoses, to fit inside the hose to keep them open at all times. The inlet hoses that are effected are the lower radiator hose in the front, and the one at the rear too, the one near the engine. This is an easy fix and John tells me that he will offer these hoses as a regular Accufab item within a day or two. Once installed inside the hose, you can stand on them with all your weight and they won't cave in.

We are working on posting a video of exactly what happens to the hoses as rpm increases. The installation is quite a task though because it requires the removal of the front, mid and rear belly pans to get access to the hoses.
 

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Last edited:

analogdesigner

GT Owner
Mark IV Lifetime
Nov 15, 2005
949
San Clemente, CA USA
Nice work guys! They are even stainless steel. I'll call soon and order a set.

Jay
GTsaver
 

Fubar

Totally ****** Up
Mark II Lifetime
Le Mans 2010 Supporter
Aug 2, 2006
3,979
Dallas, TX
Just a few questions:
1) Is there a concern about the springs breaking down over time?
2) Are you fairly certain that installing this fix doesn't create new stress on other hose sections?
3) Any idea why this doesn't affect all cars?

This has been a nagging issue for my car. I'm glad to see you guys have a fix in the works.
 

andymlow

GT Owner
May 17, 2007
286
Sarasota, FL
I'm very interested as my car is affected, but I for one would love to see some real world numbers that prove this is the fix. Show me pre and post flow rates or pre and post coolant temps etc. Thanks for effort on behalf of all the "hot" GT's out there.

Andy
 

Accufab

Well-known member
Mar 14, 2006
142
1. The springs are stainless steel so there won't be any corrosion issues over time.

2. I am not certain about stresses on other hoses, but we will address them if they arise. Certainly can't be worse than no coolant flow above 5000 rpm's.

3. It does effect all cars from the first produced to the last. It doesn't appear often because most people don't drive the cars that long at sustained rpms unless on the track.


Thanks,

John Mihovetz
 

isaakgt

GT Owner
Mark II Lifetime
Dec 20, 2005
691
Wilder, Idaho
Looks good to me. This is how they manufactured radiator hose not too many years ago. Why did they stop using springs? $$$$$$$? :shrug
 

ViperJoe

GT Owner
Mark II Lifetime
Aug 17, 2006
1,305
Washington Crossing, PA
How are the springs secured in the hoses to prevent migration, possibly into the H2O pump?
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,177
The springs can't fit inside the neck of the attach points.

John, very nice job. It is the second time (at least) you have come to the rescue of GT owners!!! (Great job on the insight/design of the axle bolts too !!)
 

Kingman

GT Owner
Mark II Lifetime
Aug 11, 2006
4,072
Surf City, USA
Is it just the spring or the hose with the spring already situated?

That looks like it would be quite a bit of work to wiggle them through without screwin up the spring.
 

isaakgt

GT Owner
Mark II Lifetime
Dec 20, 2005
691
Wilder, Idaho
Is it just the spring or the hose with the spring already situated?

That looks like it would be quite a bit of work to wiggle them through without screwin up the spring.

The springs slide into the hose. Springs have been used in radiator hoses for many years in many applications.:wink
 

analogdesigner

GT Owner
Mark IV Lifetime
Nov 15, 2005
949
San Clemente, CA USA
German fit

The trick to installing them is to rotate them clock-wise as to making the spring decrease in diameter as you work it into the hose. It looks as it should be a German fit!. Jay Gtsaver
 

BlackICE

GT Owner
Nov 2, 2005
1,416
SF Bay Area in California
Does anyone know what is involved with installing the hoses. The hose near on the water pump look easy, but the one connecting to the radiator may be a pain in the as-!

Which hose is more likely to collapse?
 

ChipBeck

GT Owner
Staff member
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 13, 2006
5,770
Scottsdale, Arizona
Easy

Which hose is more likely to collapse?

The one you didn't put the spring in.
Chip
 

BlackICE

GT Owner
Nov 2, 2005
1,416
SF Bay Area in California
The one you didn't put the spring in.
Chip

Gee, Chip you get an A in the class!

:thumbsup
 

PL510*Jeff

Well-known member
Mark IV Lifetime
Le Mans 2010 Supporter
Nov 3, 2005
4,876
Renton, Washington
Hose colapse

I have had my GT on the track more than a few times.

After scaring the poo poo out of me on the first "operation" of the coolant tank cap, I now come in after a max of 45 minutes of hard running.

Temp is bout 235. Let it cool for about 15 minutes and the out to play again.

Please put me on the Order List for your spring/hose upgrade.

There was "some" discussion at the Rally II, over a few beers, that in addition to the main hose closing off, this may also be occurring in the smaller transfer hoses from the rad back to the engine compartment. These are really hidden from view, so verifying if they are part of the solution to the higher temp's some GT's have, will be more difficult.
 

analogdesigner

GT Owner
Mark IV Lifetime
Nov 15, 2005
949
San Clemente, CA USA
Does anyone know what is involved with installing the hoses. The hose near on the water pump look easy, but the one connecting to the radiator may be a pain in the as-!

Which hose is more likely to collapse?
All things equal, the longer hose will give first.

Jay
GTsaver
 

Fubar

Totally ****** Up
Mark II Lifetime
Le Mans 2010 Supporter
Aug 2, 2006
3,979
Dallas, TX
All things equal, the longer hose will give first.

Jay
GTsaver

How about the hoses that run from the front to the back? Are they potential problems? …might as well do it all at once.
 

BlackICE

GT Owner
Nov 2, 2005
1,416
SF Bay Area in California
How about the hoses that run from the front to the back? Are they potential problems? …might as well do it all at once.

I don't know, but I am guessing that is a long metal tube.
 

Fubar

Totally ****** Up
Mark II Lifetime
Le Mans 2010 Supporter
Aug 2, 2006
3,979
Dallas, TX
I'm sure all of you guys have seen this but I just found it so...

http://www.roushind.com/news_downloads/tech_papers/2004-01-1252.pdf

good stuff
 

cobrar1339

GT Owner
Mark IV Lifetime
Feb 2, 2006
956
Diamond Bar, Ca
When they get the video posted you should have a better idea of what is happening. Originally, the one hose was closing off at the engine. When that hose was fixed, the problem transfered to the front of the car. Some of you mentioned that as a possiblility. Your thoughts are correct. Then that hose was fixed. After this, no other problems showed up or they would have been fixed as well.

Not many of us would have a GT on a rack with all the gear removed to view it properly looking for this. Running the engine high enough, over and over to see and doucument the problem. Then put apply a fix and test again. Only to find another problem and fix yet again.


I for one, believe John / Accufab has this figured out. They have been working on this for several months.

Thanks to the Accufab Team for yet another part aimed at improving the reliability of the GT.:thumbsup