problem with HOT engine

Hi
I've got problem with my V740. I've got B200K engine with mechanical
ignition and Solex carb. Auto run pretty when cold,but when it's hot it
doesn't working well. The whole coolant system is new,all parts,..the engine
is new too. When I stay in traffic jam, than is very bad working. The engine
works only when is cold, but when is hot is bad. What's wrong?? Can be too
poor mixture? and too hot temperature of engine? Thermostat and cooler and
coolant liquid are new. The valves are correct. When engine is very hot,
it;s sound very strange whet I go 2000 RPM and I push the pedal down, he
sound very bad, when it's cold it's sound very good.

Please help me,..I don't know what to do.... 99% parts in enegine deprature
is new,..the negine too (1700 km now!!!)

all the best....

 

1. Mixture too lean
2. Ignition too late
3. Thermostat bad (or incorrect replaced)
4. Air in the coolant system

Could be something else, but... try the 4 above first.

 

I would definitely check the coolant temp sensor, I've come across a couple
of bad ones lately, one I got off a straight 740 in a junkyard, makes me
think that's probably why the car ended up there in the first place.
Apparently it will cause this symptom if it goes open circuit.

 

I've think the same

10 deeg.

new one

new liquid,..without air

 

I think the cooland sensor is OK,....but anyway car goes wrong and engine
run bad, The alle cooland system is new (radiator,theromstat, coolant
liquid).

 

Since the cooling system was rebuilt, I would suspect an airlock or
air bubble in the cooling system. Have the mechanic that did the work
check.

 

But he said it's running poorly when hot, surely if a cooling system problem
were to blame, it would have to be hot enough that some major damage is
being done for it to start running poorly.

 

Or a coolant sensor is losing contact with the coolant when the thermostat
opens.

I'd double check that the radiator is full, not just the overflow reservoir.


Gary

 

reservoir.

I've checked it. Cooling system is 100% OK.

 

Jarek, if I understand correctly it overheats in traffic jams but is okay
when you get out on open road? If so, the air flow is probably the problem.

You probably have a fan on the water pump that is driven by a finned
aluminum "viscous coupler." If that coupler has lost some of the silicone
fluid it will be too weak to cool the radiator when the car is at low speed.
You can check it by trying to spin the fan by hand with the engine off. If
the fan stops within a quarter turn the coupler is working okay, but if it
goes more than 1/2 turn it is bad. Between 1/4 and 1/2 turn it is not very
good, but it is not the cause of your overheating.

I think there is also an electric fan on the front of the radiator; that
should be running when the engine gets hot (or maybe with the air
conditioning on - I forget which or both).

Mike

 

I check "in" hose - it's full on liquid. The radiator have special little
hose to take off the air bubble,...it is in highest place of the radiator.

 

problem.

No...on open road is also bad,.,...but in trafic jam is horrible.

Visco is new, it's 100% OK,...the radiator is't hot in trafic jam,because
visco works good. The radiator is also new.

I haven't got electric fan in my car,..only visco, rear radiator. It's look
like only up part of the engine, the engine's head is only too hot,..but the
block, sensor etc. is OK,..good temp.

Can I check the mixture by multimetr and lambda sond ???,...I've got old
lambda sond in my out manifold,..because manifold is from injection engine.

 

Is the cooling system holding pressure? I've seen a cracked expansion tank
cause overheating.

 

Yes,the pressure is OK,..I've chacked it

 

The radiator is not hot when the cylinder head is hot? Maybe the thermostat
was put in upside down? It is not hard to make that mistake. That prevents
the thermostat from working right so the hot water can't leave the head. If
it's a genuine Volvo thermostat it has a little hole that will let a little
water through, but just enough to let the head temperature get to the
thermostat when the engine has been cold.

 

No it's 100% OK.

Thermostat is new one also,...88 degr.

 

If the cylinder head gets extremly hot, it seems to be a problem with either
ignition timing or mixture.
Check the color of the spark plugs.
Run the car for a few minutes until the enginge gets hot.
Then unscrew one spark plug and check the color and how the spark plug
looks.(Be careful! It's very hot!!!)
If you have a Haynes manual for the car, you can find a color chart for
spark plugs on one of the last pages in the book.
Or try to find it on the Internet.

Or this one (for MC's but ok):
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

or this one:
http://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm

This may tell you something about the mixture.
Black - Too rich
White - Too lean
chocolate/grey - ok
Broken ceramic around the core - too hot (lean mixture)

Theese are the basics.

 

Is the water pump ok? I got a rock in mine once from a junkyard radiator, it
jammed the impeller which just spun on the shaft so things looked fine from
the outside but no water was being pumped.

 

If the head was that hot from a mixture/timing issue, the incandescent
glow from the exhaust manifold and turbo would give it away.

Coolant isn't flowing for some reason; if it's not a reversed thermostat,
or failed pump as someone else mentioned, it could be a weak lower radiator
hose collapsing under suction. Check by squeezing the hose from under the
car; if you can get it nearly flat with your hand, it needs replacing. It
may be possible to spot this by watching the lower hose while reving the
engine; if it deforms at all, it's bad.

Yikes! No! Never try to remove a spark plug while the head is hot; there
is a high probability of damaging the threads in the head. If that happens,
the cheap fix is a Helicoil; the expensive fix is a new head.

[ ... ]

That color chart applies when the plugs are cold, not hot.


Gary