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[michael_de]

hi , im a motor mechanic to trade however my knowledge on the mv6 is limited , yesterday i bought an r reg 3.0 mv6 for £100 as it has a few problems the main one being is the right hand bank isnt firing , i pulled the plenum chamber off and dug my way down to the plug leads, when i pulled the leads off i couldnt see the plugs , the holes were full of coolant , i know the heads and gaskets are good and obviously the water is grounding the ht but what im not sure of is , is where is the coolant coming from and is this common or am i taking the car to the knackers yard .

any ideas appreciated
thanks

p.s. i know its coolant as i tested the anti freeze level and its the same mix as the expansion tank .

[TheBoy]

I was just about to say rain running from scuttle, until you said you tested it.

There is a small coolant pipe from rear coolant bridge to throttle body, which runs over right bank (looking from front).

The HBV is a common cause for coolant loss, this tends to spray coolant all over the place, and lives behind left bank (looking from front).


Welcome to the site as well

[michael_de]

im pretty sure i checked that but access to the back of the lump isa bit tricky , what i did notice was when i took the expansion cap off coolant started to stream out the front of the bank and down the main hose but im pretty sure this is just run off , but i also found it strange that the top of the rocker cover is bone dry , you would never know there was water there until you took the leads off , is there any blanking plugs or core plugs on top of the head or between the plugs ,

thanks for the welcome

[TheBoy]

Not aware of any. I'm sure someone will be along soon to confirm.  Also, it is very rare to have core plug issues on the GM V6 unit, certainly I've never heard of them failing on this engine.

[Marks DTM Calib]

No coolant plugs n the heads on these.....

The avourites will be

1) Throttle body coolant feed hose (runs across top of 2-4-6 bank cam cvoer)
2) Leaking scuttle (unlikely as you say you have carried out an antifreeze test......what sort of test by the way?)
3) Screen washer jet pipe maybe ?

[michael_de]

i used a fancy snap on digital hydrometer , if the hoses check out is there any possibility of a crack in the head , im going to try another pressure test .
cheers

[TheBoy]

i used a fancy snap on digital hydrometer , if the hoses check out is there any possibility of a crack in the head , im going to try another pressure test .
cheers

Again, never heard of a head crack on these GM V6 units - they are a very reliable engine mechanically (usually killed by failed cambelts/tensioners)...

[Marks DTM Calib]

i used a fancy snap on digital hydrometer , if the hoses check out is there any possibility of a crack in the head , im going to try another pressure test .
cheers

Which are hit and miss on modern non-glycol based antifreeze.....anyway...it detected something!

Never seen a crack in a V6 head....

Are you positive the coolant pipe is ok......with the engine running or the coolant pressurised, was there a sign of where the leak was coming from...

[cdx25]

Rather curiously when I did my cam cover gaskets a few weeks ago I discovered just one spark plug recess to be full of what I thought was water (didnt test it for coolant etc) in pot 2.  All the others on that nearside bank were completely dry.  (Other side was full of oil but thats a different story.)

Very odd, as I couldnt see any evidence of wetness on the rocker cover tops.  

Maybe I'd better look under the plug caps that side again...

Jon

[michael_de]

hi i double checked the pipe running over the right bank , seems ok again the rocker cover is still bone dry , i pulled the leads out of the road and syphoned the liquid out , which turns out is over a quarter pint of coolant , i blanked off the pipes and hooked up my pressure tester with noresult and no pressure drop , i can't run it to pressurise as plenum in bits .

puzzled

[Markjay]

OK... maybe the coolant was left there form an earlier leak, i,e, the HBV, the leak was sorted but the spent coolant never removed, so you get a tightly sealed cooling system with coolant in the plug wells and wonder how it got there?

I suggest to dry (or, for what they cost, replace the plugs, replace the HT leads, and fire it up... if it fires than problem solved...? If it does not fire, check the DIS, if it had coolant splashed on it at some time it may not be too happy.

[michael_de]

thats a good sugestion and thats what ill do , ill change the leads and plugs as iv'e already bought them throw it back together and run it , the valve was changed six months ago - it was me that changed it !! ill do a compession test just to be safe , does anyone know what compression should be for the 3.0 with 105k

cheers

p.s. the fuel computer says 31mpg average can this be true , mainly rural runs with not much long haul

[TheBoy]

thats a good sugestion and thats what ill do , ill change the leads and plugs as iv'e already bought them throw it back together and run it , the valve was changed six months ago - it was me that changed it !! ill do a compession test just to be safe , does anyone know what compression should be for the 3.0 with 105k

cheers

p.s. the fuel computer says 31mpg average can this be true , mainly rural runs with not much long haul

31mpg is optimistic - my MV6 auto manages 25mpg, can't see it being much better. Does average 33mpg over a 2k run to France and back...

[Marks DTM Calib]

As I am sue you know, there is no specific values for any compression test as there are many factors that play a part in the results.....the important thing is that all 6 cylinders are close to each other in terms of readings.

Standard compression is often listed as 12-15Bar (i.e. you can drive a bus through the middle of it!) on these units......its the max 1bar difference between the pots thats important....(unless they are all close to zero of course )