Vannin' Home Forums Chevy How to.... blown head gasket :eek:

My thinking is that seeing as I have good compression on all cylinders that doing a leak down test wont tell me anything more.
That said I have a loan of a leak down tester so I may as well use it and see if what it tells me.

There was no sign of water on the plugs and the engine is running well and firing on all cylinders even on start up from cold so I don't think water is getting into the combustion chambers at all.
But I am losing a small amount of water and there is an oil glaze on the coolant when I drain it and a bit of mayonnaise inside the oil filler cap.

My suspicion is that it is a bad seal on the intake manifold gasket around one of the water passages between inlet manifold and one of the cylinder heads and it is weeping down into the valley from there and down into the sump. I'll pull the intake manifold and leave the heads alone, replace the intake manifold gaskets and see if there is any evidence off losing water.

I'll also check for bubbles in the rad as you suggest Wedgy.

Mayo on the oil cap could just be short trip driving in cool weather.

O once did an used oil analysis and they indicated Sodium and Potasium, indicating coolant in the oil, and as I suspected the timing chain cover and water pump bolts were allowing coolant past their threads.

Some 8 years ago I got a new all Almuinum radiator, 9 months later it was seeping coolant from teh seam where the tubes met the bottom tank. I used some of the Gm coolant fitness tabs, at 1/6th the recommeded dosage and the leak stopped. Same radiator now 9 years later. If i drain teh coolant and refill it without the Ginger root Gm coolant fitness tabs, it wll start weeping at the same exact spots. It never dripped, and was a very slow loss of coolant and if it were a black painted copper brass raditor I might not have noticed where it had been slowly weeping coolant.

My heater core is not delivering the same heat it used to though, perhaps that gibgerroot stop leak bars leaks tabs partially plugged it. perhaps the blend door insulation is shot, perhaps both. I plan to backflush it at some point. it stil gets warm, but 22f at 7K feet and 65mph this previous November, it was not effective.

So I would say to very closely inspect the radiator where the tubes and fins meet the top and bottom,or side tanks, for signs of weeping.

A radiator which does not weep would certainly be better, but I am on year 8 or 9 of the same radiator which weeped at 9 months, thanks to this specific product's efficacy.



Lot easier and cheaper than pulling the intake manifold, and if no change, well you will be changing at least a portion of coolant when you do the intake anyway. If GM still sells products in Ireland, Gm relabels this specific prduct and calls them Gm coolant fitness tabs. My landlord is a service advisor at a busy respected auto repair joint, and says most ethelyene glycol coolant using vehicles that have cooling system work done on them go out with a few of these in there to prevent comebacks.

There are similar radiator stop leak products here but not those tablets mainly liquid ones likes Wynns or Lucas. Seeing as I've done a lot of other engine dress up work and put new radiator fans on it might be time to treat my van to a new radiator. I can get this one delivered for €130 / €115 seems good value.

https://www.ebay.ie/itm/NEW-RADIATOR-FIT-CHEVY-GMC-G30-G20-G10-SAVANA-G1500-G2500-G3500-1706/192568937868?hash=item2cd600cd8c:g:KJYAAOSw9mpZ5orz

Just thinking though, if the leak was in the radiator there would be no reason for the drained coolant to have an oil glaze on it.

I think you're right about it seeping coolant into the lifter galley.
Stock radiators usually have a trans cooler built into them. But any exchange of fluid there would show up pretty quick on the trans dipstick.
Have the heads been resurfaced or the block decked by chance? Cutting the block or heads lowers them in relation to the manifold and can cause a mismatch at the intake mating surface. But something like that is usually accompanied by a vacuum leak. Anyway, did the intake bolts line up and screw in okay without a hassle? Do you have any oil seepage at the front or rear of the intake?
Maybe the gaskets just slipped a little. It does seem odd that a relatively new set of gaskets would leak coolant but not leak vacuum.
LIke you said, just thinking out loud here.

The new radiator you linked, the picture appears to show connections for a tranny fluid cooler in one side tank and an engine oil cooler in the other plastic side tank, though the description says it only has the ATF cooler.

Does your existing radiator have an engine oil cooler?

Might be the source of the sheen, if so. If not, could be the tranny cooler leaking into the coolant.

If you have an older copper brass radiator, well lets say the plastic tanked aluminum models are not really built to last. If there are still shops In Ireland than can recore radiators there, they might be a better option. Seems all those shops around here have been killed off by 70$ chinesium radiators.

Regarding the stop leak products. I've read nothing good about any, but the crushed gingerroot tabs I posted a pic of, and these might be responsible for my heater core not transferring heat as it once did.

Current radiator only has the trans cooler so it's unlikely to be caused by that as Catfish said. I'll hold off on a new radiator but maybe send it out to be re-cored over the winter when I take the van out of use. Everything is still pointing to the inlet manifold gasket. It don't remember any issue with bolts lining up but it may be just a small failure in the gasket.

So finally got round to doing a leak down test and all cylinders came up as good.

Rocker covers are covered in emulsion on the top so it looks as though water is getting past the inlet manifold gasket at one of the water jacket holes , dripping down into the sump and being sprayed up with oil through the push rods to coat the inside tops of the rocker covers. Gonna pull the inlet manifold and investigate that next week.

Remember next set gaskets, it's regular maintenance to check the bolts. When new,check after warm up, check at end of day, check in a couple days, check couple weeks, check twice a year. Yup it's a chevy, don't forget the header bolts.