help needed,running rover3500 in my dax for 5 years no problems.put in a set of adjustable push rods with one and a quarter turns to set the pre-load ,now it boils up within a mile or two.exhaust pipes are now blue from heat. check for air in the system half a dozen times,check timing(ok),fueling ok,thermo ok also checked compressions ok.at a total loss now and no hair left to pull out.any ideas out there
v8 overheating
- Thread starter bluebuggsy
- Start date
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is it just the pushrods you changed? they can be notoriously difficult to shift air locks from though
I would first look for any breather pipes not refitted since you worked on it.Sounds like it is running very lean to heat it up enough to blue the exhausts.If nothing obvious,consider refitting the original pushrods in case the new ones are having an effect on valve timing enough to cause hot running.Of course,you could have a coincedence,like a head gasket or thermostat failure,not connected with the mods.
Does replacing pushrods mean the heads come off? sounds like you have no water flow to boil that quickly. if you replaced gaskets maybe you have a blockage from blue mastic sealer from the rebuild. Was the radiator removed, disturbed. they silt up and moving them can loosen the silt and make a blockage.
Either way i'd say cooling system first, just a small tuning change (ie small % bhp increase) shouldn't suddenly render the cooling system massively inadequate.
Either way i'd say cooling system first, just a small tuning change (ie small % bhp increase) shouldn't suddenly render the cooling system massively inadequate.
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IF head was removed - it could be that the new gasket was put on upside down and has blocked a couple of transfer holes for the coolant. However, it is unusual to have to remove head to fit new pushrods unless you want to remove the cam followers as well.
My money will be on the valve clearances being too small. Less air = less fuel = running lean = extra heat (not so much fuel to cool the charge on entry to the cylinder)
If the exhaust valve clearance is also too small the exhaust won't be venting cleanly so the valves will get hotter and push the engine temp through the roof. The hotter gases will stay in the manifolds longer as the overall flow is reduced hence the colour of the downpipe.
You are running the risk of burnt valves and warped head. I agree that you should put the old pushrods back and see what happens.
Point to check - did you fit new rocker arms? They wear a ridge in the centre which doesn't allow a set of feeler gauges to be inserted properly to gap the valve clearance. Try setting it with a "click adjuster" vernier type tool for more accurate results. Grinding out the ridge sometimes works but it can remove the case hardening and ruin the rocker arm.
My money will be on the valve clearances being too small. Less air = less fuel = running lean = extra heat (not so much fuel to cool the charge on entry to the cylinder)
If the exhaust valve clearance is also too small the exhaust won't be venting cleanly so the valves will get hotter and push the engine temp through the roof. The hotter gases will stay in the manifolds longer as the overall flow is reduced hence the colour of the downpipe.
You are running the risk of burnt valves and warped head. I agree that you should put the old pushrods back and see what happens.
Point to check - did you fit new rocker arms? They wear a ridge in the centre which doesn't allow a set of feeler gauges to be inserted properly to gap the valve clearance. Try setting it with a "click adjuster" vernier type tool for more accurate results. Grinding out the ridge sometimes works but it can remove the case hardening and ruin the rocker arm.
thanks for all the help.
ron gamma prob right as set gaps on wrong lift ,ie to small. have changed heads due to blue smoke(clouds of the stuff).mate of a mate gave me a set of 3900 heads ,will they fit 3500 block with 3500 gasket.many thanks for all the help out there. When sorted will post for all the v8 out there.
ron gamma prob right as set gaps on wrong lift ,ie to small. have changed heads due to blue smoke(clouds of the stuff).mate of a mate gave me a set of 3900 heads ,will they fit 3500 block with 3500 gasket.many thanks for all the help out there. When sorted will post for all the v8 out there.
It seems to me as if there are two faults!
Retarded ignition and lack of water flow.
If the stat is open and the pump operating correctly there will be a fairly small temperature differential across the rad. Perhaps 20-30°C max from top to bottom.
If there is no flow then the bottom of the rad will be pretty cool as there will only be thermal circulation like the very early cars.
Tony
Retarded ignition and lack of water flow.
If the stat is open and the pump operating correctly there will be a fairly small temperature differential across the rad. Perhaps 20-30°C max from top to bottom.
If there is no flow then the bottom of the rad will be pretty cool as there will only be thermal circulation like the very early cars.
Tony
it has all come down to a sticky thermo. opened ok in hot water.but after fitting new heads was still overheating, so started checking from scratch ,what do you know the thermo would not open in pan of boiling water.so now i know always check and check again
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