GM engine overheats -

Check for failed Head Gasket,
Cracked Blocks, Cracked Heads,Warped Heads

Symtoms? any one or more of the following may be seen..
- overheating at highways speeds,
- loss of coolant but no leaks,
- crud in the surge tank / reservoir,
- water in the oil, check the OIL DIPSTICK!
- white "smoke" (steam),
- increasing oil level.
- smell of coolant but no visible leak,


Prevention Advice ?

CHANGE THE COOLANT at 24 months or less, ANY coolant, ANY CAR.
Coolants, including Dex-Cool have often failed to do their metal protection
job beyond 24 months. this failure is usually connected with an incident of
loss of coolant and overheating at some point in the history of the engine.


OTHER items that create overheating - more often than headgaskets

not listed in any order of importance:

- clogged heater core - if one hose is much hotter than the other one your heater core may be plugged,
- lower radiator hose w/o inner metal support - collapsing,
- clogged radiator,
- clog or leak in the hose to the purge/resevoir tank,
- thermostat is sticky. read FAQ on Dex-CoL,
- failed thermostat,
- thermostat installed backwards,
- defective NEW thermostat,
- defective radiator cap,
- failed water pump,
- defective water pump with impeller installed backwards,
- used water instead of the 50/50 coolant mix,
- used pure coolant instead of the 50/50 mix,
- use of tap water instead of distilled water has created deposits,
- wrong drive belts,
- slipping drive belts,
- clogged catalytic, failed catalytic
- clogged tailpipe
- radiator fans not working
- engine timing,
- air or gas in the system
- cavitation at water pump / AIR in system
- rebuilt radiators, cleaned & flushed fail due to weak coolant chamber
vanes that collapse & shut when the radiator gets HOT.
etc ...

other things make peope THINK the car overheats although the coolant temp may be normal:
- defective coolant sensor
- climbing temp upon hard driving, ie hills, acceleration, headwind, extreme ambient temp.

Check the thermostant? watch temperature at initial warm-up usually overshooting
the operating temp of the thermostat, than drop back and stabilize. a good sign of a good stat.

Running test - exhaust gas leakage into cooling system
Start the engine, cold and with the pressure cap off the pressurized surge tank.
Look for for bubbling or "false boilling" in tank.
Bubbling may be a sign that combustion pressure is entering the cooling system

TORQUE WRENCH TEST - to confirm that the head gasket needs to be replaced due to
headbolt failure, pull the valve covers, use a torque wrench set on 75 lbs to check if
any of the headbolts will turn. If any do turn, headbolts have failed and are stripped.
Time for a teardown and threadserts.

OIL DIPSTICK TEST - pull the dip-stick and see of your OIL level is raising. This could
confirm that coolant is moving from teh cooling system to the cranckcase. Also, you may
see signs of water.

Pressure cooling system - coolant leakage into combustion chambers
Use a cooling system pressure tester pump. See the Craftsman cooling system pressure
tester model #70888 - about $100. picture at end of post.
Hold it at 15 PSI for 6 to 10 hours, pump it up if the pressure drops.
In the meantime, pull the plugs.
After several hours of holding the pressure, use starter to rotate the engine with the plugs out.
Look for coolant spraying out from the spark plug ports
That would be a very strong sign of a coolant leaks.

Pressurize combustion chamber - exhaust gas leakage per cylinder into cooling system
With the cooling system full, apply 120 PSI shop air to each of the
combustion chambers, through the spark plug port.
Make an adapter out of an old spark plug shell and run shop air to the port.
or buy a ready made adapter ..(see adapter picture below)
Rotate the engine so that all the valves for each cylinder are closed.
Inspect the coolant in the surge tank for bubbling.
If the chamber holds the 120 PSI with no bubbling then chances are all is fine.

Pressurize cooling system - exhaust gas leakage into cooling system
ORIGINAL: belagatyo

Has a pressure test been done (cooling system) ? It is a very simple but very useful test. It is basically a hand-pump with a sensitive pressure gage that you attach to the surge reservoir and pressurize the system. It it leaks down over time, there is a leak. Some pin-holes won't leak until high pressure is reached.

Also, when you get the engine running while the gadget is attached, and you see the needle oscillating, that means that there is a "connection" between the coolant passages and the combustion chamber - bad news!



Combustion gas test - reactant dye.
This product will answer the of loss of coolant and leaks into the coolant system.
It wont give you the where or why of the leak or the source of coolant loss, but
will tell you there is a problem.
There may be other products, this is provided as a sample not a recommendation.
(usual disclaimer - dont own any of it, dont know anyone there)


Block Test Kit
You can see it locate combustion leaks
without guess work! Tests in seconds for:

* Cracked Blocks
* Leaky Gaskets
* Cracked Heads
* Warped Heads

When fluid turns from BLUE to YELLOW, a combustion leak is present
http://www.rxauto.com/order.htm



local://upfiles/2893/FF1E9666E57140C29988C8259D571D66.jpg





ok .. dug into the dark corners of my Proto box and found it !
pressure test adapter.

THE ADAPTER -

it has two size threads, maybe 14mm & 18 mm. I dont know what the
part number is. I believe it came from the PROTO truck, (now owned by
Stanley) but it is not marked. It fits the GM (327 ci), Ford (302 ci) &
Mopar (340 ci), we had a compression gauge attached but dont remember
if that gauge was part of it or we added it. too long ago.



http://www.cadillacforum.com/upfiles/2893/5144D33383AD411A99960B91DF2A4BF8.jpg



by Craftsman

Universal cooling system pressure tester that eliminates the need for almost all system adaptors. Complete with 4 double-ended cap adaptors allowing 8 different caps to be tested. Spare bladder, manual, 3 neck extensions and 4 cap adaptors, blow-molded storage case Suitable for marine applications Fluid drain tube lets coolant return to reservoir or safely collect for recycling Contents: analyser, pressure pump with 0-30psi gauge, air supply hose, drain hose Locate leaks from head gaskets, radiator/heater cores, welch plugs/housings, water pumps Features universal fitment for fast, efficient system testing Test cap relief pressure and seal condition
http://www.cadillacforum.com/upfiles/2893/57B4B7CD67854E5BBA69DE338B166F5F.jpg



local://upfiles/2893/5144D33383AD411A99960B91DF2A4BF8.jpg
local://upfiles/2893/57B4B7CD67854E5BBA69DE338B166F5F.jpg

I post this unk article for one purpose and one purpose only.

To show you that there is a difference between the ealry 4100 and the later (1984+) 4100's which
did not suffer the ills of the early models.

Should you be buying a pre-'84 car with a 4100, have the engine checked for symtoms of overheating ( read the end
of the article). These noted issues do not apply to the Allante 4100's since those came much later, in 1987.

However, IF it was me buying ANY aluminum engine car, ANY maker, ANY year, I would certainly test
the engine for head gasket integrity. Aluminum engines, simply stated, are not forgiving of even one overheating
episode. We all knew that back in the 80's, but people seem to have forgotten that simple fact.

IF your aluminum engine starts getting HOT, shut her down, PULL OVER. Dont attempt to drive the extra
two miles home. Even, or specially, the NorthStar engines - camel mode or not. OF course, all IMHO !



by unk

All HT-4100 engines had significant reliability problems, specifically rapid main bearing and camshaft lubrication (wear) failures; however, those of the first years, mainly 1982 and 1983, were troublesome engines. The problems were caused by engine coolant entering the engine's crankcase from the intake manifold gaskets at the heads. Once the coolant mixed with the engine oil, the lubrication dropped significantly.
Intake manifold coolant leaks were common on early HT-4100 engines with as little as 30,000 miles. The "design" solution used by Cadillac was to replace the intake manifold bolts with a bolt with a smaller diameter shank in conjunction with a Bellville (spring) washer. However, once coolant leaks were discovered, the intake manifold had to be removed to replace the gaskets and also to use the GM fix (bolt/washer kit).

After two years of production, Cadillac began installing and recommending the field installation of GM Coolant Supplement which was basically a "stop leak" type of product to try to seal the engine at its gasket to prevent oil and coolant from mixing. This product came as tablets which were crushed and added to the coolant. It was only partially successfull in preventing oil/water problems and could actually clog the cooling system if too much was instilled.

The vast majority of HT4100's did not make 60,000 miles without severe bearing knock or complete engine failure and complete engine failure was known to occur in as few as 30,000 miles. Cadillac replaced hundreds of thousands of these engines under warranty; so many, in fact, that it was common to see bad HT4100's stacked like cordwood in service departments across North America.

Also, in engines with no discernable problems, one overheating episode often would destroy the engine as it was nowhere near as forgiving of high temperatures as a cast iron engine.









.

ORIGINAL: slowroll

There was a recall 99086 involving 1999 Northstar and Aurora V8 for head bolt holes being drilled to deep. A condition where head bolts could come loose. There is a vin break of less than 20k cars to be inspected. Engines that failed inspection were to be replaced. VIN breakpoints:

DeVille XU791675 - XU802142

Seville XU938976 - XU940640

Eldorado XU613134 - XU614972

Only some of the engines would fail inspection.

A $3,000 table ?



ORIGINAL: stomper

What to do with an ENGINE after the headgaskets fail




http://www.cadillacforum.com/upfiles/3799/FA70132674B946588A75BAD890439FA1.jpg

WATER PUMP

ORIGINAL: Katzmans Caddy

Put on the heater full blast. If you get heat water is circulating through system and pump is fine. If low heat or no heat impellers are corroded and pump is done. You might also see some leakage from the seep hole on the water pump cover left front of engine.